Chemistry 151 Week 4 – Critically Analyzing Scientific Data
College of the Canyons Fall 2020
Name ______________________
Date ________________ Section_________________________________
Critically Analyzing Scientific Data
Activity adapted from Miller, D. M; Chengelis Czegan, D.A.Integrating the Liberal Arts and Chemistry: A
Series of General Chemistry Assignments to Develop Science Literacy. J. Chem. Ed, 2016, 864-869
In today’s fast-paced, technology-driven, 24-hours news cycle society, it seems information is coming at
you faster than you can keep up. Much of this information is “scientific” news, stories, or advances and can
sound very legitimate…but that is not always the case. As an informed listener or reader, you need to be
able to take in the information being presented, critically and objectively analyze it, and make your own
judgement as to the validity of the conclusions that are being reported.
In science there are many factors that affect whether a news source, website, or story is credible. This
activity is designed to help you assess what information should be taken seriously versus information being
hyped to help attain some other purpose. You will apply those skills to analyze some real-life, current
scenarios.
Hallmarks of Reliable Scientific Research
When scientists observe some phenomenon that is interesting to them they often use the scientific method
to learn more about that process. The scientific process consists of the following steps:
Observation
This process provides a framework to analyze new findings, but it does not ensure the validity of any
findings. A valid scientific study is characterized by additional features that serve to challenge and
scrutinize any new findings prior to publication. These characteristics are:
- Representative samples (large n, reproducible data)
- Reproducibility (control groups, cause vs correlation, biases & placebo effects)
It is unavoidable that there will be some amount of variation in results from a scientific experiment. This
arises from random error sources, which are outside of the control of the researcher. This could be changes
in the environment (temperature fluctuations for example) or just the inability to exactly repeat precisely
how you took a measurement. Random error affects scientific data’s reproducibility or precision: the
ability to obtain the same result every time an experiment is performed. The good news about random error
is that it usually averages out statistically (for every temperature fluctuation where it got a little warmer,
there will likely be a fluctuation where it got a little cooler).
If too few measurements are used to draw conclusions, random errors present in the experiments may be
misinterpreted as true phenomena, and a scientist may draw unwarranted conclusions from the data. This
means when you are hearing about a new scientific discovery, information, or finding, if it is unclear how
many times the experiment was repeated, or even worse if it was clearly not repeated at all, or very small
sample sizes were used, then you should be skeptical about the results.
Chemistry 151 Week 4 – Critically Analyzing Scientific Data
College of the Canyons - Peer Review (valid interpretation of results, well-designed and performed studies)
This process of peer-review helps to ensure that all published data is valid, significant, and original.2 This
means that the science that comes out of this process is more than just some scientist’s opinion; it’s been
analyzed, scrutinized, and supported by a variety of scientists in the field.
When a group of researchers believe that they have data and information worth sharing with the world, they
will submit their paper to be published in a journal. These are different than magazines, newspapers or
online articles because while those articles are hopefully thoroughly researched, they are not critiqued by
other, non-affiliated, objective experts in the same field. Not all journals are peer- reviewed either, but those
that are send the papers they receive to a team of experts to read the paper before they agree to publish it.
These experts critically examine the scientific data presented to determine if it is:
• valid/credible
• significant
• original2
If enough of the peer-reviewers agree that the science presented is credible, reproducible, and valid, then
the journal will likely agree to publish the results. If the peer-reviewers find issues, concerns, or other errors
in the data, the journal will not publish the study as presented. Often, the journal requests that the scientists
edit or amend the original research – often requiring that additional experiments be carried out! – before
agreeing to publish the paper. In a sense, peer-reviewers are the referees for scientific research and
conclusions, and if you find information in a peer-reviewed journal, you can have more confidence in the
validity and accuracy of the data and conclusions that are being presented.
One limitation to the peer-review process may come if someone is trying to publish truly brand-new, neverbeen-seen-before data. If there are no other obvious ‘experts’ in a field, it may be hard to find reviewers
who can critically and objectively assess the data and the conclusions2. Usually as long as all of the data is
clearly presented, and logically and honestly analyzed and discussed, even non-expert reviewers will be
able to recognize it as valid and credible science and support its publication.
For more information on peer review, see the handout listed in the references (2).
Procedure
Part I: Recognizing Reliable vs Unreliable Evidence
Begin by reading the attached handout titled, “A Rough Guide to Spotting Bad Science”1 and answer the
following questions:
Chemistry 151 Week 4 – Critically Analyzing Scientific Data
College of the Canyons - From the twelve points outlined on the handout, rank the three points that you feel are most detrimental
to the validity of a scientific study. Then discuss your choices with your partner. Whenyou and your
partner agree on the top three points, write them in the table below and write 1-2 sentences explaining
why you ranked each as very detrimental. - The handout mentions that both a control group and a blind study are ways to improve the reliability of
a scientific study. What is the difference between a control group and a blind study?
Point Explanation
Chemistry 151 Week 4 – Critically Analyzing Scientific Data
College of the Canyons - The difference between correlation and causation was discussed as well. In your own words, what is
the difference between the two, and how do you think you can try to assess whether something you’re
reading is correlation or causation? - What is peer review? What is peer review important?
- What is one challenge with peer review?
Part II: Searching and Assessing Reliable Sources
Visit the following websites and based on what you’ve learned about identifying credible, reproducible,
and peer-reviewed data, rank them on a scale from 1-5 for their reliability (1 is the least reliable source, 5
the most). All of the sources deal with the safety of the artificial sweetener, Aspartame.
x https://www.fda.gov/food/ingredientspackaginglabeling/foodadditivesingredients/ucm397725.ht m
x http://articles.mercola.com/sites/articles/archive/2011/11/06/aspartame-most-dangerous- substance-addedto-food.aspx
x https://en.wikipedia.org/wiki/Aspartame
x http://www.equal.com/products/equal-original/
x http://thepopularman.com/aspartame-detox-and-withdrawal/
Chemistry 151 Week 4 – Critically Analyzing Scientific Data
College of the Canyons - Use the table provided below to rank the websites, and provide justification for your ranking. Include
in the justification any of the 12-points to look for that may be relevant, as well any other factor that
you used in your decision.
Website Ranking (1-5) Justification
FDA
Mercola
Wikipedia
Equal
Popularman
Chemistry 151 Week 4 – Critically Analyzing Scientific Data
College of the Canyons
Part III: Journal Article Critique
Read the attached article, published in Physiology and Behavior, and answer the questions that follow: - Article analysis
a. What was the goal of the research?
b. What conclusions did the researchers draw from their study?
c. What evidence did the scientists present that supported their claims? - Article Critique
a. Was this article published in a peer-reviewed journal?
Chemistry 151 Week 4 – Critically Analyzing Scientific Data
College of the Canyons
b. Identify any of the 12-points/criteria used to assess scientific findings that you see arise in this article.
Provide the specific example from the article that matches the particular point, and in 1-2 sentences explain
whether this was something that was positive (they avoided one of the 12 common faults) or negative (they
utilized one of the 12 common faults in their findings).
c. Read the ‘Acknowledgements’ carefully – who funded this research? What do youthink that means about
the objectivity/validity of the study?
d. Do a quick internet search to try and find who founded/funded the EuropeanHydration Institute. Does this
make you more or less confident in the scientific findings?
Chemistry 151 Week 4 – Critically Analyzing Scientific Data
College of the Canyons
e. Based on your response to questions (a) – (e), make a conclusion about the overall validity of this scientific
data and the author’s conclusions. Make sure you fully explain your conclusion and how you came to it. - Do you think that just because a scientific study was funded or initiated by a company/corporation with a
potential conflict of interest, that it should immediately be assumed to invalid and skewed? If yes, explain
why you feel this way. If not, explain what you think it does mean to you, the reader, if you discover a
scientific study has ties toanother organization.
Mild hypohydration increases the frequency of driver errors during a
prolonged, monotonous driving task
Phillip Watson a,c,
⁎, Andrew Whale a,b
, Stephen A. Mears a
, Louise A. Reyner a,b
, Ronald J. Maughan a
a School of Sport, Exercise and Health Sciences, Loughborough University, Leicestershire LE11 3TU, UK
b Sleep Research Centre, Loughborough University, Leicestershire LE11 3TU, UK
c Department of Human Physiology, Vrije Universiteit Brussel, Brussels B-1050, Belgium
HIGHLIGHTS
• Mild hypohydration has been shown to cause impaired cognitive function and altered mood.
• This study reports an increase in driver errors with mild dehydration.
• Error incidence increased over time, but occurred at a greater rate following fluid restriction
• Higher subjective feelings of thirst, as well as impaired concentration and alertness were also apparent
• Driver education programmes should also encourage appropriate hydration practices.
article info abstract
Article history:
Received 13 November 2014
Received in revised form 13 March 2015
Accepted 13 April 2015
Available online 16 April 2015
Keywords:
Cognitive function
Dehydration
Fluid balance
Road traffic accident
The aim of the present study was to examine the effect of mild hypohydration on performance during a
prolonged, monotonous driving task.
Methods: Eleven healthy males (age 22 ± 4 y) were instructed to consume a volume of fluid in line with
published guidelines (HYD trial) or 25% of this intake (FR trial) in a crossover manner. Participants came to the
laboratory the following morning after an overnight fast. One hour following a standard breakfast, a 120 min
driving simulation task began. Driver errors, including instances of lane drifting or late breaking, EEG and heart
rate were recorded throughout the driving task.
Results: Pre-trial body mass (P = 0.692), urine osmolality (P = 0.838) and serum osmolality (P = 0.574) were the
same on both trials. FR resulted in a 1.1 ± 0.7% reduction in body mass, compared to −0.1 ± 0.6% in the HYD trial
(P = 0.002). Urine and serum osmolality were both increased following FR (P b 0.05). There was a progressive
increase in the total number of driver errors observed during both the HYD and FR trials, but significantly
more incidents were recorded throughout the FR trial (HYD 47 ± 44, FR 101 ± 84; ES = 0.81; P = 0.006).
Conclusions: The results of the present study suggest that mild hypohydration, produced a significant increase in
minor driving errors during a prolonged, monotonous drive, compared to that observed while performing the
same task in a hydrated condition. The magnitude of decrement reported, was similar to that observed following
the ingestion of an alcoholic beverage resulting in a blood alcohol content of approximately 0.08% (the current UK
legal driving limit), or while sleep deprived.
© 2015 The Authors. Published by Elsevier Inc. This is an open access article under the CC BY-NC-ND license
(http://creativecommons.org/licenses/by-nc-nd/4.0/). - Introduction
Under ‘normal’ conditions, an individual's total body water (TBW)
fluctuates throughout the day, but overall daily water balance is generally maintained through a series of interrelated factors which control
intake and output of water. The homeostatic regulation of salt and
water balance normally acts to limit excursions in TBW to no more
than about 1% per day [24]. Nevertheless, there are several routinely encountered situations that act to either increase fluid losses (e.g. illness,
exposure to heat/humidity, diuretics), or serve to restrict fluid
intake (e.g. access to beverages and/or latrines). Over time, one, or a
combination, of these factors results in the progressive reduction in
TBW. The ensuing hypohydration causes a reduction in the circulating blood volume and an increase in plasma osmolality, which are
typically proportional to the magnitude of decrease in TBW [32].
Populations at particular risk of hypohydration are the very young,
those engaged in professions where fluid homeostasis is regularly
Physiology & Behavior 147 (2015) 313–318
⁎ Corresponding author. Fax: +32 26292876.
E-mail address: pwatson@vub.ac.be (P. Watson).
http://dx.doi.org/10.1016/j.physbeh.2015.04.028
0031-9384/© 2015 The Authors. Published by Elsevier Inc. This is an open access article under the CC BY-NC-ND license (http://creativecommons.org/licenses/by-nc-nd/4.0/).
Contents lists available at ScienceDirect
Physiology & Behavior
journal homepage: www.elsevier.com/locate/phb
challenged and the elderly. Limited data are available on the prevalence of hypohydration, but there is evidence to suggest that this
may be relatively common among sections of the elderly population
[24].
Mild hypohydration can cause symptoms such as headache, weakness, dizziness and fatigue, and generally makes people feel tired and
lethargic, with lower self-reported ratings of alertness and ability to
concentrate [36]. Body water losses have been shown to impair performance in a variety of tests of both physical and mental performance. Evidence suggests that either starting exercise in a hypohydrated state, or
allowing hypohydration to accrue during exercise, will result in an increase in subjective feelings of exertion, or this likely contributed to
the reduction in exercise performance [24]. As little as a 2% reduction
in body mass due to insufficient hydration can also result in impaired
cognitive function, with changes in mood state and modest reductions
in concentration, alertness and short-term memory reported [1,24]. In
addition to the established physiological consequences of hypohydration,
the generally unpleasant symptoms of hypohydration (e.g. dry mouth,
thirst, headache) may directly produce a negative effect on mood state
[2,12]. In fact, some authors maintain that dehydration-associated
impairment of tasks with a large cognitive component is driven primarily
by the discomfort and distraction associated with these symptoms [6].
Data quantifying the hydration practices of regular drivers is scarce,
but assessments of hydration status and reported beverage intakes
among employees in a variety of workplace settings highlighted that a
significant proportion of employees report to work exhibiting signs of
dehydration [25]. A large proportion of those individuals also remained
in a state of hypohydration at the end of their shift, citing restrictions on
when and where they could consume fluid and access to toilet facilities
as the primary barriers to increasing water intake. It is likely that driving
in a hot car will lead to significant losses of water over the course of a
long journey, but these data are not readily available in the scientific
literature. Even in an air-conditioned car, evaporative water losses
from the skin and lungs are likely to accumulate during a long drive
due to exposure to dry air because of the increased vapour pressure gradient. Taking these points into consideration, the European Hydration
Institute recommends the regular ingestion of non-alcoholic beverages
during long automobile journeys to help to reduce road fatigue [10].
These guidelines are likely to be sound, but anecdotal reports suggest
that many drivers avoid drinking adequately, with a view to limiting
the need for bathroom stops during long journeys.
While it is widely acknowledged that the use of alcohol or drugs
among drivers increases the risk [29] and the severity [3] of road traffic
accidents, there are currently no scientific evidence linking dehydration
to an increased incidence of traffic accidents. At present only one recent
study has investigated the possible effects of dehydration on simulated
driving performance [20]. Again the primary focus was to examine the
effects of moderate quantities of alcohol on aspects of driving performance, but this group also suggested a possible interaction between
alcohol consumption and dehydration. The authors suggested that
alcohol-induced impairments in cognition, and consequently on simulated driving performance, would be greater when individuals were
also in a state of dehydration. Although the results of this study failed
to identify any significant impact of hydration status on driving performance, it is worth noting that the simulated driving task employed was
short (15 min) and was set in a suburban environment.
An estimated 1.2 million people worldwide are killed as a result of
road traffic accidents each year, with around 50 million people also injured annually [40]. Driver error is by far the largest cause of these accidents, accounting for approximately 68% of all vehicle crashes in the UK
[7,8]. Factors including failing to look properly, misjudging another
driver's path or speed and driver distraction are cited in the top ten
most common causes of traffic accidents [7,8]. During long and monotonous driving, most drivers progressively show signs of visual fatigue
and loss of vigilance [4]. Hypohydration has been shown to result in
altered mood and deficits in aspects of cognition, it is reasonable to
assume that dehydrated drivers may be more susceptible to errors in
judgement and/or the successful execution of motor skill. With this in
mind, the aim of the present study was an initial exploration of the
effects of mild hypohydration, on performance during a prolonged, monotonous driving task where aspects of cognition relevant to driving
(e.g. response times and loss of vigilance) are likely to be challenged. - Methods
2.1. Participants
Twelve healthy males were recruited to participate in this randomised
crossover design study. All participants were experienced drivers; having
driven for over 2 years on a full licence and for more than 2 h/week. Prior
to volunteering, participants received written information regarding the
nature and purpose of the study and a written statement of consent
was signed. One participant completed all trials but was excluded from
the final results after displaying a high propensity to fall asleep during
the driving task (perhaps caused by sleep deprivation). Physical characteristics (Mean ± SD) of the remaining 11 participants were: age 22 ±
4 y; height 1.75 ± 0.06 m; and body mass 77.4 ± 10.0 kg. This study
was approved by the local Ethical Advisory Committee (REF: R14-P12).
2.2. Experimental design
Each volunteer visited our laboratories on three separate occasions.
The first visit was a familiarisation trial that involved the completion
of the same driving task undertaken in the experimental trials. This
was intended to enable the participants to become accustomed with
the study protocol and limit any possible learning effect apparent with
the use of the driving simulator. This was followed by two experimental
trials. All trials were separated by at least 7 days and experimental trials
were completed in a randomised order. Participants were provided
with a customised diary to record dietary intake and physical activity
during the 24 h before the first experimental trial and were asked to
replicate this on the day prior to the subsequent experimental trials.
During each trial period (as illustrated in Fig. 1), participants were
asked to record dietary intake in a food and beverage record diary,
using the portion size method. No restrictions on routine or food/
beverage intake, other than those mentioned below, were enforced
during this period, as the aim was to mimic free-living conditions. To
help ensure the volunteers were adequately hydrated, they were
instructed to consume at least 2.5 L of fluid, spread evenly across the
day [9]. No strenuous exercise or alcohol consumption was permitted
in the 24 h before, as well as during, each trial.
2.3. Experimental protocol
Each experimental trial took place over two days, as illustrated in
Fig. 1. On day 1, volunteers visited the laboratory in the morning after
an overnight fast (10 h, with no food or fluid permitted). A urine sample
was obtained and body mass measured to the nearest 10 g in minimal
clothing (underwear). Volunteers then sat for 15 min, before a 5 mL
blood sample was collected from a superficial antecubital vein. During
the 15 min of seated rest, subjective feelings related to thirst, hunger,
concentration and alertness were assessed using a series of 100 mm visual analogue scales [36]. Volunteers were then free to leave the laboratory with the instruction to replicate their food intake of the pre-trial
standardisation day. During the hydrated (HYD) trial volunteers continued to consume at least 2.5 L of fluid, spread evenly across the day.
During the fluid restriction (FR) trial, only 25% of the HYD fluid intake
was permitted; this was expected to result in a ~1% reduction in body
mass over a 24 h period [36].
Participants then returned to the laboratory the following morning
after an overnight fast (10 h, with no food or fluid permitted). A urine
sample was obtained and body mass measured in minimal clothing.
314 P. Watson et al. / Physiology & Behavior 147 (2015) 313–318
After sitting for 15 min, a 5 mL blood sample was then collected from a
superficial antecubital vein. The same visual analogue scales were
also completed at this time and a heart rate telemetry band was
positioned (Polar RS400, Kempele, Finland). Participants were then provided with a standardised dry breakfast (2 cereal bars; Alpen, Weetabix
Ltd., Kettering, UK), providing 1052 kJ, 42 g of carbohydrates, 7.6 g of fat
and 3.8 g of protein. During the HYD trial they were given a volume of
plain water to drink with breakfast (500 mL), but on the FR trial only
a very small volume was provided (50 mL). They were then fitted
with electroencephalogram (EEG) and electrooculogram (EOG) electrodes. Electrodes were attached for two channels of EEG, with interelectrode distances carefully maintained by using the ‘10–20 EEG montage’ (main channel C3–A1, backup channel C4–A2), and there were
two EOG channels (electrodes 1 cm lateral to and below left outer canthus and 1 cm lateral to and above right outer canthus; both referred to
the centre of the forehead).
One hour following breakfast, volunteers began a driving simulation
task, similar to that described in several publications [11,30,31]. The
task comprised of a 2 h continuous drive in an immobile car with a
full-size, interactive, computer-generated road projection of a dull monotonous dual carriageway, each carriageway having two lanes. The
road also had a hard shoulder and simulated auditory ‘rumble strips’
(incorporated into white lane markings) either side of the carriageway
and a barrier separating the carriageways, with long straight sections
followed by gradual bends. Slow moving vehicles were met occasionally, and these had to be overtaken. Drivers were instructed to remain
within their lane unless overtaking. During the HYD trial volunteers
were be provided with 200 mL of fluid every hour, and on the FR trial
only 25 mL was made available each hour. Immediately following the
drive, volunteers then sat for 15 min, before a 5 mL blood sample was
collected from a superficial antecubital vein. A final assessment of subjective feelings related to thirst, throat dryness, hunger, concentration
and alertness was undertaken, before a urine sample was obtained
and body mass was again measured in minimal clothing.
2.4. Analysis
2.4.1. Dietary intake
Nutritional analysis of food intake records was undertaken using
commercially-available nutritional analysis software (NetWISP v4.0,
Tinuviel Software, UK). Total water intake from all food and drink, as
determined from food composition tables within the database, was
the primary focus. The contribution of metabolic water to total body
water was not accounted for, as this was assumed to be consistent
across both trials. Energy, macronutrient and caffeine intakes were
also examined to ensure consistency across trials.
2.4.2. Driving related measures
Instances of lane drifting or late breaking are the most common
manifestation of driver error, and a car wheel touching (or crossing)
the rumble strip or lane line was identified as a driving ‘incident’.
These were classified as ‘minor incidents’, whereas ‘major incidents’ included cases where the car completely leaves the lane, hits the barrier or
another car. Split-screen video footage of the roadway and driver's face
(filmed by an unobtrusive infrared camera) enables the cause of the
incident to be determined. Those due to sleepiness (e.g. excessive
blinking, eye closure, eyes rolling upwards or vacant staring ahead)
were logged as ‘sleep-related incidents’. Non-sleep related incidents
(driver distraction, fidgeting or looking around) are also recorded.
2.4.3. EEG and EOG
EEGs and EOGs were recorded using “Embla” (Flaga Medica Devices,
Iceland) and spectrally analysed using “Somnologica” (Flaga) in 4 s
epochs. EEG low and high band-pass filtering at N20 Hz removed slow
eye movements and muscle artefacts. Increases in EEG power in the
alpha (8–11 Hz) and theta (4–7 Hz) ranges indicate increasing sleepiness
[22] and reduced vigilance [4]. EEG power in this (4–11 Hz) frequency
range was then averaged in one-minute epochs. To remove individual
differences in these EEG power levels and to permit better comparison
between conditions, these data were standardised for each participant
by taking the difference between each epoch and mean value for that
person's EEG power during the first 30 min of the HYD trial, divided by
the standard deviation around that mean [11,31].
2.4.4. Blood and urine samples
Blood samples collected throughout the experimental protocol were
drawn into dry syringes before being dispensed into plain tubes and left
to clot at room temperature for 1 h. These samples were then centrifuged at 3000 g for 10 min to yield serum. When urine samples were
obtained, participants were instructed to empty their bladder as
completely as possible into a collection container. The volume of each
void was determined, and a 5 mL aliquot was retained in a sterile collection tube. All urine and serum samples were stored at 4 °C for a maximum of 7 days before being analysed for osmolality using freezing
point depression (Gonotoc Auto; Berlin, Germany).
Fig. 1. A schematic representation of the experimental protocol describing the methods employed to manipulate of hydration status on days 1 and 2 of the trials. Arrows indicate the measurement of body mass, urine and serum osmolality undertaken upon arrival laboratory at the start of days 1 & 2 of the experimental protocol, as well as the end of the driving protocol.
P. Watson et al. / Physiology & Behavior 147 (2015) 313–318 315
2.5. Statistical analysis
On the basis of the results of previous investigations undertaken
using the same experimental model [11,18,30,31], we estimated a 90%
probability of detecting a difference in total errors of at least 32 with a
sample size of 11 subjects (G-Power 3.1, Dusseldorf, Germany). Data
are presented as mean ± standard deviation (SD) unless otherwise stated. Driving incidents and the EEG data were averaged into 30 min
epochs, as described by Reyner et al. [31]. The distribution of the data
was first assessed using the Shapiro–Wilk test. Differences in the total
number of driver errors recorded during each trial, as well as the baseline measures used to check pre-trial standardisation, were assessed
using paired sample t-tests. Cohen's d effect sizes (ES) for the differences in driver error rate were also determined. To identify differences
in normally-distributed data collected throughout each trial, two-way
(time-by-trial) ANOVA were employed. Where a significant interaction
was apparent, pair-wise differences were evaluated using the
Bonferroni correction. For the purpose of hypothesis testing, the 95%
level of confidence was predetermined as the minimum criterion to
denote a statistical difference (P b 0.05). - Results
Pre-trial body mass (t = 0.391, P = 0.692), urine osmolality
(t = −0.216, P = 0.838), serum osmolality (t = 0.338, P = 0.574)
were the same on both trials, suggesting that the participants were in
a similar state of hydration before the start of each trial. Pre-trial dietary
energy (HYD 12.6 ± 1.2 MJ; FR 12.3 ± 1.8 MJ; t = 0.297, P = 0.742) and
caffeine (HYD 157 ± 51 mg; FR 131 ± 46 mg; t = 0.412, P = 0.742) intakes were also not different. Participants also started both trials
reporting the same subjective feelings of thirst, throat dryness, hunger,
alertness and ability to concentrate; further supporting this view.
Total water intake from all sources during day 1 of the HYD trial
was 3.0 ± 0.2 L, compared to 0.9 ± 0.1 L ingested during the FR trial
(t = 10.647, P b 0.001). This comprised 2.6 ± 0.2 L from beverages
and 0.4 ± 0.2 L from foods in the HYD trial, whereas 0.5 ± 0.2 L and
0.4 ± 0.1 L was ingested through beverages and foods respectively
during the FR trial. Caffeine intake was lower during the FR trial
(55 ± 12 mg) compared to the HYD trial (208 ± 49 mg; P = 0.017).
FR during day 1 resulted in a 1.1 ± 0.7% (range −0.7 to −2.3%) reduction in body mass, compared to −0.1 ± 0.6% (range +1.1 to −0.7%) in
the HYD trial (F = 38.482, P = 0.002). The 24 h restriction of fluid intake
resulted in an increase in both serum (F = 92.042, P = 0.007) and urine
osmolality (F = 207.904, P b 0.001; Fig. 2).
The number of driver errors made during the trials, both minor and
major incidents, grouped into 30 min blocks, is illustrated in Fig. 3. There
was a progressive increase in the total number of driver errors observed
during the HYD trial, with significantly more incidents recorded during
the last 30 min period (17 ± 16), than in the first 30 min (7 ± 8; F =
3.587, P = 0.043). However, the frequency of driver error increased to
a greater extent throughout the FR trial (F = 8.043, P = 0.008). FR resulted in a marked increase in the total number of driving errors, with
47 ± 44 and 101 ± 84 recorded during the HYD and FR trials respectively (t = −4.549, P = 0.006; ES = 0.81). Four major incidents were recorded over the course of the study, but these were evenly distributed
between the HYD and FR trials. There was no clear relationship between
the number of errors made during the FR trial and the degree of dehydration accrued (r2 = 0.18; P = 0.544); it is likely that there is insufficient statistical power to detect such an effect with the number of
participants recruited, nor was the experiment designed to examine
this question.
The analysis of the EEG data is presented in Fig. 4. There was a
progressive increase in alpha (8–11 Hz) and theta (4–7 Hz) activity
throughout both the HYD and FR trials (F = 4.528, P = 0.038), indicative of greater sleepiness and perhaps reduced vigilance. The magnitude
of change tended to be greater in the FR trial, but this response just
failed to reach significance (F = 2.998, P = 0.062).
There was no change in thirst perception over the course of the HYD
trial, but self-reported ratings of thirst increased by 107 ± 17% throughout the FR trial (F= 80.920, P b 0.001). The same response was apparent
when examining the perceived feelings of throat dryness. Perceived
ability to concentrate (−39 ± 17%; F = 22.475, P b 0.001) and alertness
(−48 ± 26%; F = 6.845, P = 0.016) had also reduced over the course of
the FR trial, but these were both significantly lower at the end of the
Fig. 2. Urine (top) and serum (bottom) osmolality throughout the HYD and FR trials. *
denotes a significant difference between trials at the corresponding time point
(P b 0.05). Data are presented as mean ± standard deviation.
Fig. 3. The total number of driver errors made during each 30 min period of the HYD and
FR trials. * denotes a significant difference between trials at the corresponding time point
(P b 0.05). Data are presented as mean ± standard deviation.
316 P. Watson et al. / Physiology & Behavior 147 (2015) 313–318
drive during the FR trial than compared with the HYD trial (both
P b 0.001). - Discussion
4.1. General discussion
Driver error is by far the largest cause of road traffic accidents, accounting for approximately 68% of all vehicle crashes in the UK [7,8].
During motorway/highway driving, drivers tend to progressively
show signs of visual fatigue and loss of vigilance [4]. Since deficits in
TBW are associated with altered mood and decrements in aspects of
cognitive function, it is possible that dehydrated drivers may be prone
to making more errors in judgement and car handling. The results of
this exploratory study suggest that mild hypohydration, induced
through a short-term period of fluid restriction, produced in a significant increase in minor driving errors during a prolonged, monotonous
drive, compared to that observed while performing the same task in a
hydrated condition. Mild dehydration can produce negative changes
in mood state and modest reductions in concentration, alertness and
short-term memory [1,2,12,14]. While there remains some uncertainty
whether these responses result from a physiological impairment caused
by the reduction in total body water and electrolyte imbalance, or are
simply due to the discomfort and distraction associated with dehydration, these subtle changes in mood and cognition mostly likely explain
the decrement in driving performance observed.
Water accounts for 50–60% of body mass in most healthy individuals, and maintaining water balance is essential for health. Body water
turnover rate, a function of fluid losses (respiratory water, sweat,
urine, faeces) and fluid gain from food, beverages and metabolic
water, is highly variable between individuals with typical values of between three to six litres/day reported in the literature. The homeostatic
regulation of salt and water balance normally acts to limit excursions in
total body water to no more than about 1% per day [5]. Exposure to environmental extremes (particularly heat and humidity) and prolonged
physical activity, as well as some nutritional (fluid restriction, alcohol)
and pharmacological (diuretics) interventions can significantly accelerate fluid losses over time. Hypohydration causes a reduction in the
circulating blood volume, a reduction in stroke volume and an elevated
heart rate at a given exercise intensity [13,26]. There is also evidence of
direct effects of hypohydration on the central nervous system [28,39],
which may contribute to these observed changes in both mood and
cognitive function.
The American College of Sports Medicine qualifies mild hypohydration as body mass losses exceeding 1%, and as such are deviations
in total body water that may be encountered routinely by adults during
daily activities [33]. While data quantifying the hydration practices of
regular drivers is scarce, when hydration status has been assessed in a
variety of workplace settings, a significant proportion of employees report to work exhibiting signs of dehydration [25]. In addition, it is likely
that driving in a hot car may lead to significant losses of water over the
course of a long journey, but again these data are not readily available in
the scientific literature. While it has been suggested that drivers should
aim to regularly ingest non-alcoholic beverages during long automobile
journeys to help to reduce road fatigue [10], and caffeine containing
beverages, including coffee and energy drinks, are regularly promoted
to counteract driver fatigue [30], factors such as limited free access to
fluids and desire to avoid stops for bathroom breaks mean that drivers
may place themselves at greater risk of dehydration.
At present only one study has examined the effects of dehydration
on simulated driving performance [20]. This particular study was primarily designed to investigate a possible interaction between
exercise-induced dehydration and alcohol consumption, as the authors
suggest that many people tend to consume alcoholic beverages following participation in sports. No effect of dehydration was observed, but it
is worth noting that the driving task employed was particularly short
(15 min). While several studies have reported decrements in aspects
of cognitive function with dehydration [1,2,12,14], there are a number
of conflicting reports suggesting little or no change in cognition following a variety of dehydration protocols [21,37,38]. Innate intelligence and
life experience of familiar day-to-day tasks, such as driving, result in
functionally more efficient cognitive networks and therefore provide a
cognitive reserve [34]. This acts as a buffer providing resilience to cope
with increasingly complex tasks while still functioning adequately,
and also delays the onset of clinical manifestations of neurodegenerative disorders such as Alzheimer's disease. There is evidence that
individuals are able to tolerate a degree of dehydration without any
measureable impairment in cognition by increasing the degree of
brain activation required for a given task [21]. It appears likely that in
the present study the task was sufficiently complex and long lasting to
overcome this reserve capacity and result in a measurable decrement
in cognitive performance. It is worth noting that while some studies
do not report significant differences in task performance with varying
levels of dehydration, these data suggest that losses of body water
and/or electrolyte imbalances do appear to produce decrements in aspects of brain function underlying important cognitive processes.
4.2. Implications and limitations of the study
Driving performance in the present study was assessed through a
simulated driving task, rather than ‘real world’ on-road driving. The
use of a driving simulator allowed us to study long, monotonous, and
uninterrupted driving task, but it is difficult to know how to translate
the driving errors measured during a simulated drive to the likelihood
of accidents occurring on the road. The simulator employed in the
present study has been internally validated against an instrumented
real car circulating a race track, and it has been employed in several published studies investigating the link between tiredness and driving performance publications [11,18,30,31]. The car cabin environment,
including commands and instruments were identical to an operative
car, but it should be recognised that a driving simulation is not real driving. While participants were instructed to drive as diligently as they
would on the road, the consequences of a minor error made during a
simulation are clearly not the same as would be experienced while driving at speed on a motorway [4]. However, the present data do suggest
that decrements in vigilance, decision making and mood, as apparent
from the EEG data and the reported subjective feelings, are likely to
have a significant influence on driving behaviour. This is likely to translate into a greater potential for errors in both simulated and real world
Fig. 4. EEG alpha + theta power (4–11 Hz) averaged every 30 min and normalised against
each individual's power in these ranges, by taking the difference between each minute's
epoch and the individual's mean value over the first 30 min of the HYD data, and dividing
this by the standard deviation around the mean of that 30 min of data. Data are presented
as mean ± standard deviation.
P. Watson et al. / Physiology & Behavior 147 (2015) 313–318 317
settings, and consequently influencing the possibility of road traffic
accidents.
Driver fatigue and sleep-related vehicle accidents account for a considerable proportion of all vehicle accidents, especially those on motorways and other monotonous roads [17]. These types of accidents are of
particular concern since the possibility of a fatality is approximately
three times greater than encountered in general road accidents [7,8].
Many road traffic accidents are preventable, and a variety of national
initiatives and targets to reduce road deaths and serious injuries have
been implemented in recent years [7,8]. Interventions that have been
implemented both within the UK and elsewhere to prevent or reduce
the occurrence of accidents on the road and the severity of injuries
sustained, include changes to the road environment, media safe driving
campaigns, drink driving campaigns, stricter enforcement of legislation
relating to roads, and finally targeted driver education programmes. The
later approach aims to enhance safe driving skills through increased
awareness of the dangers involved and improved recognition of driving
hazards. While the effects of alcohol consumption and driving while
tired is mentioned in these courses, there is no mention of other factors
that drivers should be aware of to maintain attention and vigilance.
In conclusion, the results of this initial exploratory study suggest that
mild dehydration, induced through a short-term period of fluid restriction, produced in a significant increase in minor driving errors during a
prolonged, monotonous drive, compared to that observed while
performing the same task in a hydrated condition. Due to the nature
of the experimental protocol, it is unclear whether this response was
caused by prior the fluid restriction, difference in fluid intake during
the drive or combination of both these factors. Further work is warranted to examine contribution of these factors to the response observed.
The level of dehydration induced in the present study was mild and
could easily be reproduced by individuals with limited access to fluid
over the course of a busy working day. To provide some context to the
magnitude of decrement in stimulator performance reported, a similar
increase in driver error rate has been observed when driving following
the ingestion of an alcoholic beverage resulting in a blood alcohol content of approximately 0.08% (the current UK legal driving limit), or
while sleep deprived [19]. There is no question that both drink-driving
and driving while tired increases the risk of road traffic accidents [40],
and many countries have instigated national campaigns to educate
drivers of the associated risks. Given the present findings, perhaps
some attention should also be directed to encouraging appropriate hydration practices among drivers.
Acknowledgements
This work was funded in part by a grant from the European Hydration
Institute (EHI). The EHI did not directly contribute to the study design;
the collection, analysis and interpretation of data or in the writing of
the manuscript.
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???
C BY NC ND
A Rough Guide to
SPOTTING BAD SCIENCE
© COMPOUND INTEREST 2015 - WWW.COMPOUNDCHEM.COM | @COMPOUNDCHEM
Shared under a Creative Commons Attribution-NonCommercial-NoDerivatives licence. - SENSATIONALISED HEADLINES
Aa
Article headlines are commonly designed to
entice viewers into clicking on and reading
the article. At times, they can over-simplify
the fndings of scientifc research. At worst,
they sensationalise and misrepresent them. - MISINTERPRETED RESULTS
News articles can distort or misinterpret the
fndings of research for the sake of a good
story, whether intentionally or otherwise. If
possible, try to read the original research,
rather than relying on the article based on
it for information. - CONFLICTS OF INTEREST
Many companies will employ scientists to
carry out and publish research - whilst this
doesn’t necessarily invalidate the research,
it should be analysed with this in mind.
Research can also be misrepresented for
personal or fnancial gain. - CORRELATION & CAUSATION
Be wary of any confusion of correlation and
causation. A correlation between variables
doesn’t always mean one causes the other.
Global warming increased since the 1800s,
and pirate numbers decreased, but lack of
pirates doesn’t cause global warming. - UNSUPPORTED CONCLUSIONS
Speculation can often help to drive science
forward. However, studies should be clear
on the facts their study proves, and which
conclusions are as yet unsupported ones. A
statement framed by speculative language
may require further evidence to confrm. - PROBLEMS WITH SAMPLE SIZE
In trials, the smaller a sample size, the
lower the confdence in the results from
that sample. Conclusions drawn can still be
valid, and in some cases small samples are
unavoidable, but larger samples often give
more representative results. - UNREPRESENTATIVE SAMPLES USED
In human trials, subjects are selected that
are representative of a larger population. If
the sample is diferent from the population
as a whole, then the conclusions from the
trial may be biased towards a particular
outcome. - NO CONTROL GROUP USED
In clinical trials, results from test subjects
should be compared to a ‘control group’ not
given the substance being tested. Groups
should also be allocated randomly. In
general experiments, a control test should
be used where all variables are controlled. - NO BLIND TESTING USED
To try and prevent bias, subjects should
not know if they are in the test or the
control group. In ‘double blind’ testing,
even researchers don’t know which group
subjects are in until after testing. Note,
blind testing isn’t always feasible, or ethical. - SELECTIVE REPORTING OF DATA
Also known as ‘cherry picking’, this involves
selecting data from results which supports
the conclusion of the research, whilst
ignoring those that do not. If a research
paper draws conclusions from a selection
of its results, not all, it may be guilty of this. - UNREPLICABLE RESULTS
Results should be replicable by independent
research, and tested over a wide range of
conditions (where possible) to ensure they
are consistent. Extraordinary claims require
extraordinary evidence - that is, much more
than one independent study! - NON-PEER REVIEWED MATERIAL
Peer review is an important part of the
scientifc process. Other scientists appraise
and critique studies, before publication
in a journal. Research that has not gone
through this process is not as reputable,
and may be fawed.
x x
Being able to evaluate the evidence behind a scientifc claim is important. Being able to recognise bad science reporting, or
faults in scientifc studies, is equally important. These 12 points will help you separate the science from the pseudoscience.