This study examined the relationships between exercise, sleep, and caffeine consumption among 16 undergraduate students. It found that number of hours exercised was positively associated with number of hours slept during the school week. It also found that caffeine consumption was negatively associated with number of hours slept during the school week. There was no significant association found between caffeine consumption and number of hours exercised. The study collected data using a questionnaire that gathered demographic information as well as data on sleep habits, exercise routines, and caffeine intake.

1. The Relationship Between Exercise, Sleep Patterns, and Caffeine Consumption 1
The Relationship Between Exercise, Sleep Patterns, and Caffeine Consumption
Among 3rd
Year College Undergraduates
Rob Errico
Psychology Department, Seattle University,
Seattle, WA
2011

2. The Relationship Between Exercise, Sleep Patterns, and Caffeine Consumption 2
Abstract
The current study examined the relationship between caffeine consumption, exercise routines,
and sleep patterns among 16 junior-standing undergraduate students enrolled full-time at a university in
northwestern Washington. General demographic information was gathered along with the participants'
average weekday caffeine consumption, number of hours slept on school nights, and average hours
exercised during the week. Employment information and extracurricular involvement was also included.
Running Spearman's rho analyses showed a significant positive association between number of hours
exercised and number of hours slept during the school week; Spearman's rho analyses also showed a
significant negative association between caffeine consumption and number of hours slept during the
school week. There was no significant association between caffeine consumption and number of hours
exercised. Future research could account for more factors such as participants' intensity of exercise,
caffeine content of beverages consumed, and confounding variables such as prescription medications
and physical disabilities. Lastly, future research should pool information from a much large sample size.

3. The Relationship Between Exercise, Sleep Patterns, and Caffeine Consumption 3
Introduction
There exists an intricate relationship between sleep patterns, exercise routines, and the quantity
of caffeine consumed by an individual. Each influences the other in ways that dramatically affect a
person’s overall physical and psychological health. Inadequate exercise leads to fatigue and poor
psychological functioning; poor psychological functioning may drive a person towards excessive caffeine
consumption which in turn leads to poor sleep. On the other hand, caffeine can boost psychological
performance, and can also increase exertion effort when exercising which lends to improved sleep
quality. For optimal health, a balance must be found. The relationships between caffeine, exercise and
sleep will now be examined more closely using relevant research.
Exercise positively affects sleep quality and diminishes sleep disturbances (Sin, Ho, & Chung,
2008; Digdon, 2007; Brand, et al., 2009) in addition to improving cognitive functioning (Brand et al.,
2009; Sin et al., 2008), emotional well-being (Brand et al., 2009; Digdon, 2007), and overall physical
health (Brand et al., 2009; Doherty & Smith, 2004). Better sleep generates improved cognitive
functioning (Brand et al., 2009), emotional well-being (Brand et al., 2009; Digdon, 2007), and physical
health (Brand et al., 2009; Doherty & Smith, 2004). Caffeine commonly serves as a method of coping
with sleepiness and general fatigue (Digdon, 2007; Sin et al., 2008). For some people, caffeine helps to
wake them up in the morning, especially 'night owls' - people with a late-night circadian preference
(Digdon, 2007). Caffeine attaches to adenosine receptors in the brain and inhibits their uptake of
adenine (Doherty & Smith, 2004). Adenosine receptors are partly responsible for our sleep-wake cycle
and also control levels of neural activity (Doherty & Smith, 2004). Caffeine acts as an ergogenic
(performance enhancing) and analgesic (pain suppressing) substance for both physical and mental
activity (Doherty & Smith, 2004). Caffeine is utilized more efficiently by a regular exerciser due to the

4. The Relationship Between Exercise, Sleep Patterns, and Caffeine Consumption 4
production of adenosine receptors throughout the body during and after physical exercise, thus
resulting in more receptors for caffeine to bind to (Doherty & Smith, 2004). With more receptors to bind
to, caffeine wakes up the user more and for a longer period as well as suppresses pain and improves
physical and cognitive performance more effectively. Excessive consumption of caffeine can cause poor
sleep or insomnia (Sin et al., 2008; Digdon, 2007). Based on the above articles, the most beneficial
interaction of all three factors involves a regular exercise regiment, a routine sleep pattern concordant
with personal circadian preference, and moderate caffeine consumption at least 4 hours before bedtime
to prevent sleep disturbances.
Because college students are the population in this study, the sample will likely comprise of
sleep-deprived individuals (Harris, 2009; Digdon, 2007). College is an obligation-filled and stressful
period in life and time-management has not always been mastered yet. In addition to time-
management, methods of coping with sleepiness are varied and not always conducive to physical and
mental health (Harris, 2009; Digdon, 2007). College students' ability to maintain healthy habits regarding
exercise, sleep, and caffeine may be frequently compromised by imposing priorities such as academic,
occupational, and extracurricular commitments.
Current research by Brand et al. (2009) on the relation between exercise and caffeine use
supports the theory that regular exercise facilitates healthy sleep patterns, improved psychological
functioning, and a decreased dependence on substances. However, a curious byproduct of researching
this relationship has revealed that caffeine has a marked positive affect on exercise endurance (Doherty,
2004). Nonetheless, the strong correlation between caffeine use and poor sleep quality should incite
special consideration when using caffeine for physical performance-enhancing purposes. With poor
sleep, reliance on substance abuse may follow, “either to induce sleep (alcohol, cannabis) or to reduce

5. The Relationship Between Exercise, Sleep Patterns, and Caffeine Consumption 5
daytime sleepiness (caffeine)” (Brand, et al., 2009, p. 133).
Despite the depth of each of the studies cited here regarding sleep patterns, exercise routines,
and caffeine consumption, there is a scarcity of research examining the interdependence of all three.
The present study seeks to reveal more about the delicate balance involved between healthy caffeine
use, exercise, and sleep patterns. College students vary in circadian preference, amount of sleep
necessary for normal psychological functioning, and tolerance to caffeine (Digdon, 2007). Despite these
differences, I hope to illustrate strong negative correlations between caffeine consumption and sleep as
well as strong positive correlations between exercise and sleep.
Methods
Participants
Junior year full-time college students enrolled at a private four-year university responded to a
questionnaire that was distributed through a combination of social networking sites, email
correspondence, and classroom visits. A total of 61 people were contacted and 16 questionnaires were
returned with signed consent forms. The data from all 16 questionnaires was complete and was used in
the present study; however, exercise information and caffeine consumption for 2 cases (#1 & #16) were
excluded from the analyses due to containing extreme scores.
The average age of the sample was 20.50 years (SD = .966). There were 6 males (37.5%) and 10
females (62.5%) who participated. The average GPA for fall quarter was a 3.19 on a 4.0 scale (SD = 2.43).
The average GPA for winter quarter increased to a 3.28 on a 4.0 scale (SD = 2.03). Participants in the
current study worked an average of 13.63 hours per week (SD = 9.71) and were involved in
extracurricular activities for an average of 8.69 hours (SD = 10.14).

6. The Relationship Between Exercise, Sleep Patterns, and Caffeine Consumption 6
Measures
Participants provided the hours of sleep they get for each night of the week. Only the hours
slept on nights during the school week were included in the data analysis. A School Night Sleep scale was
developed for the current study. It had good internal consistency, with a Cronbach’s alpha coefficient
reported of .771.
Information regarding exercise habits was gathered by asking participants the number of times
they exercise per week as well as the total number of hours they exercise per week.
The questions regarding caffeine were partitioned by beverage type (because of variations in
caffeine content) and when, during the week, they were consumed (during the school week or over the
weekend). This information was compiled to obtain a score that represented each participant’s overall
caffeine consumption during the school week. Weekend caffeine consumption was not included in the
data analysis.
The weekday caffeine consumption questions were investigated for internal consistency. The
scale earned a Cronbach’s alpha of .56. However, 25 cases were automatically excluded. In situations
where so few cases are considered, the mean inter-item correlation value can substitute as a reliable
determinant of a scale’s internal consistency. The inter-item correlation shows a score of .66 with values
ranging from .31 to 1.0. All scales' scores were averaged.
Procedure
The 27-item questionnaire asked about general demographic information, employment status,
and extracurricular involvement. Questions regarding caffeine consumption, sleep patterns, and
exercise habits were all aimed at gathering information about participants’ most recent trends in these
areas.

7. The Relationship Between Exercise, Sleep Patterns, and Caffeine Consumption 7
Results
Preliminary Analyses
While the study began with the intention of having an equal distribution of males and females, it
later became apparent that this would not have made sense to do with the limited number of cases
collected. Therefore, no consideration was given to differences between genders despite literature
suggesting that males and females respond differently to caffeine consumption, exercise, and sleepiness
(Brand, et al., 2009; Doherty & Smith, 2004).
Case 16 had more than one declaration in two separate colleges (i.e., had 2 majors and 2
minors), so this information was excluded from the analysis due to the data analysis plan not having a
score that could account for this. Case 1's 'total number of hours exercised' score was excluded because
it appeared to be an outlier.
Hypothesis #1: Exercise is Associated with School Night Sleep Patterns
The relationship between the number of hours exercised per week and the total hours of sleep
during the school week was investigated using the Spearman’s rho correlation coefficient. There was a
strong, positive correlation between the variables, r(14) = .55, p <.05. See Figure 1 for a depiction of the
association. The number of hours exercised per week helps to explain nearly 30.25% of the variance in
participants' total hours of sleep during the school week.
Hypothesis #2: School Week Caffeine Consumption is Associated with School Night Sleep Patterns
The relationship between the total number of caffeinated drinks consumed during the school
week and the total number of hours of sleep during the school week was investigated using the
Spearman’s rho correlation coefficient. There was a strong, negative correlation between the variables,

8. The Relationship Between Exercise, Sleep Patterns, and Caffeine Consumption 8
r(14) = -.51, p <.05. See Figure 2 for a depiction of the association. The total number of caffeinated
drinks consumed during the school week helps to explain 26.01% of the variance in participants' total
number of hours of sleep during the school week.
Discussion
The current study's findings supported existing research that adequate exercise encourages
healthy sleep patterns. Research points to the positive impact regular exercise has on psychological
functioning, emotional well-being, and perceived levels of energy (Brand et al., 2009) suggesting that
those who get adequate exercise would desire smaller average quantities of caffeine – although there
are many exceptions to this extrapolation. Digdon (2008) says that some people are considered evening
types, also known as 'night owls', according to their circadian preferences. Night owls prefer to stay up
late and wake up late, so, for them, caffeine serves as a crucial component for early-morning
functioning. The majority of college students fall in the night owl category (Digdon, 2008) and caffeine is
very important for them, especially those with early classes. However, the effects of caffeine fade after
4 hours (Sin et al., 2008) so morning-time caffeine consumption alone does not explain how caffeine is
such a prevalent culprit of sleep disturbance (Digdon, 2008). The current study showed that people who
exercised less also slept less and that people who slept less consumed more caffeine.
Research indicates that sleepiness is the most common reason for caffeine consumption
(Digdon, 2008). Personal traits that cause poor sleep for college students include an unfavorable
attitude toward life, poor self-confidence, negatively oriented mental and physical arousal (i.e. tense,
irritable, or nervous), unfavorably aggressive behavior (i.e. internalizing, over-controlling, or evasive),
negative self-perception of body sensations, unfavorable focusing habits, and unfavorable rumination
habits (Brand et al., 2009). According to Brand (2009), athletes who engage in vigorous exercise on a

9. The Relationship Between Exercise, Sleep Patterns, and Caffeine Consumption 9
regular basis experience less daytime sleepiness, less depression and anxiety, more positive
psychological well-being, and have higher self-esteem. These findings suggest that the psychological
causes of poor sleep are remedied by the powerful benefits exercise has on quality of sleep. This may be
because exercise causes an increase in slow wave sleep, a reduction in light sleep, and shortened sleep
onset latency (the time it takes to fall asleep after closing one's eyes) (Brand et al., 2009). Accordingly,
those who do not get adequate exercise would need to resort to other means to get these benefits. This
helps to explain the link between exercise and caffeine consumption, despite the current study failing to
find a significant association between the two. If participants were not getting adequate exercise, they
appeared to rely more on caffeine to make up for poorer psychological functioning, less energy, and
poorer sleep patterns.
Literature on the topic of exercise and sleep generally advocates for athleticism (being on a
sports team, or having an exercise regimen that is strictly adhered to by the individual on his or her own)
(Brand et al., 2009; Doherty & Smith, 2004). Athletes may experience better sleep quality due to “a
more structured wake/sleep pattern, which normally promotes healthy sleep” (Brand et al., 2009, p.
140). Athletes often have trainers, physicians, psychologists, or various other forms of social support
that “contribute to a more structured life, very likely including sleep patterns” (Brand et al., 2009, p.
140). These aspects ultimately play into the theme of the importance of time-management. A structured
life allows for a more efficient utilization of time and can prevent the disruption of sleep patterns and
exercise routines. Lastly, athletes are usually knowledgeable about the importance of good sleep for
physical and mental recovery after exhausting exercise (Brand et al., 2009). This is in concordance with
the current study's findings showing that participants involved in sport-related extracurricular activities
or those who were committed to 5 hours or more of weekly exercise reported regular sleep patterns

10. The Relationship Between Exercise, Sleep Patterns, and Caffeine Consumption 10
(i.e. a consistent 7 or 8 hours of sleep over the entire week) as opposed to other participants who
reported irregular sleep patterns.
Digdon (2007) explores the topic of being knowledgeable about personal physical and mental
health in an article examining how circadian preference can determine the methods used by college
students to cope with sleepiness. “Circadian preferences are influenced by the endogenous (internal)
circadian pacemaker, ‘zeitgebers’ such as exposure to light (external cues that synchronize an
organism's internal clock to the Earth's 24 hour light/dark cycle), behavioral rhythms, lifestyle
obligations and choices, and developmental maturation” (Digdon, 2007, p. 417). As mentioned before,
college students are predominantly evening types (Digdon, 2007). 'Night owls' engage in less physical
activity, rely on caffeine more often, and get less natural light than intermediate or mornings types, also
known as 'Larks' (Digdon, 2007). As these night owls develop ways to cope with sleepiness, bad habits
are easily formed (Digdon, 2007). As habits take root, a willingness to try viable alternatives diminishes
and thus caffeine becomes the most common method of coping with sleepiness while exercise and
spending time outdoors are rated as less and less effective (Digdon, 2007). “College students who are
evening types have different beliefs about methods for coping with sleepiness than college students
who are intermediate [or morning types] in circadian preference” (Digdon, 2007, p. 423). In the current
study, those who reported less than 6 hours of sleep a night or slept a total of 30 hours or less over the
course of the school week also reported significantly higher caffeine use (8 or more caffeinated
beverages per school week) and unsatisfactory exercise habits (2 hours or less a week). There were no
exceptions, 30 hours of sleep appeared to be the cutoff point for healthy caffeine use and adequate
exercise. The insidious nature of caffeine addiction is revealed by night owls' sleepiness ratings as no
sleepier than intermediate types despite getting quantitatively less sleep and sleep of poorer

11. The Relationship Between Exercise, Sleep Patterns, and Caffeine Consumption 11
(subjective) quality. This is due to caffeine providing them a sense of temporary relief from their actual
fatigue (Digdon, 2007). Digdon (2007) speculates that perhaps night owls are quite aware of the dangers
their coping methods pose:
Perhaps sleepiness is considered a necessary consequence of ambition and of getting ahead in
an individualistic, competitive society. If this is the case, it may lessen student motivation to
eliminate sleepiness, especially if students also underestimate the negative effects of sleepiness
on performance (p. 424).
Knowing about healthy sleep habits, healthy methods of coping with sleepiness, and one's own
convictions about the effectiveness of each coping method all help to maintain the proper balance
necessary for healthy and responsible caffeine use. Although the present study did not ask about
participant's ratings of their sleepiness or opinions about the coping methods they use, their habits were
apparent by the information they reported: sleep-deprived participants neglected to exercise enough
[or, perhaps, vice a versa – the study suggests only association, not causation] and relied heavily on
caffeine.
Limitations
The results of the current study must be cautiously considered due to several limitations. The
most significant limitation of this study is its very small sample size. A total of 61 questionnaires were
distributed but only 16 were returned. For both analyses that were run to examine the research
hypotheses, only 14 cases were considered. Furthermore, the samples themselves represented only
junior-standing college students. Thus, the generalizability of this study's results is quite small.
Other limitations arose from the questionnaire's simplicity. The study did not account for
prescription medications; a significant confounding variable in this category would be pharmaceutical

12. The Relationship Between Exercise, Sleep Patterns, and Caffeine Consumption 12
stimulants. Likewise, there were no questions regarding learning disabilities, psychological disorders, or
physical disabilities that may have explained why some participants seemed to neglect getting adequate
exercise or had poor sleep patterns. For example, chronic depression is known to cause insomnia in
some cases (Brand et al., 2009 & Digdon, 2007).
In a similar vein, questions regarding participant's circadian preferences and school/CRO
schedules would have helped explain sleep patterns and caffeine use where getting adequate sleep or
exercise may have been very difficult with certain schedules and may have been conflictual with other
commitments – thus representing circumstantial restrictions rather than a participant purposefully
neglecting exercise or sleep.
The rigorousness of exercise and the stress level of participant's lives were not accounted for –
both of which effect quality of sleep and likelihood of caffeine reliance. The results of this study did not
account for gender differences and this presents another limitation to the findings. Females and males
respond differently to vigorous exercise as well as the effects of caffeine (Brand et al., 2009 & Doherty &
Smith, 2004). Tolerance to caffeine may have also effected the accuracy of the findings because some
individuals who were consuming several cups of caffeinated beverages a day may have reached a level
of tolerance that caused them to only feel the effects as much as an infrequent caffeine drinker
consuming one cup or less a day. Similarly, the caffeine beverage index could have been inaccurate due
to caffeine content variations across different beverage venders (i.e. a cup of coffee from Starbucks
compared to a cup from 7-11).
Conclusion
Adequate exercise is associated with healthy sleep patterns. Adequate sleep is associated with
healthful and responsible caffeine consumption. Because college students vary in their circadian

13. The Relationship Between Exercise, Sleep Patterns, and Caffeine Consumption 13
preference and school schedules, which sometimes conflict, caffeine can serve as a helpful means of
remaining awake and alert throughout the morning. When it is not required for normal functioning (aka,
when user is not addicted), it appears that moderate caffeine consumption can be used for its analgesic
and ergogenic properties at least 4 hours before bedtime without significantly affecting sleep patterns
or exercise routines (Doherty & Smith, 2004). While this is not nearly a large enough sample to safely
generalize to the greater college population, the results from this study suggest that the ideal balance is
as follows: per school week, junior year college students should get at least 5 hours of exercise, 35 hours
of sleep, and consume no more than 5 caffeinated beverages. Why not suggest students get a full nine
hours of sleep per night, exercise at least one hour every day and consume caffeine only when
necessary? As mentioned before, most college students are 'night owls' in their circadian preference,
are sleep-deprived because of many commitments, responsibilities, and circumstantial disadvantages
and distractions, and are in the process of adjusting to adult life. Thus, an 'ideal balance' must remain
realistic by accounting for all the time-consuming factors in a college student's life while striving to make
the best of what limited time they have. Future research can address the limitations of this study by
administering a more comprehensive questionnaire to a larger population, and perhaps follow up with a
second questionnaire several months later to account for differences in sleep patterns and exercise
habits in response to different schedules and the maturation of participant's methods of coping with
sleepiness.

14. The Relationship Between Exercise, Sleep Patterns, and Caffeine Consumption 14
References
Brand, S., Gerber, M., Beck, J., Hatzinger, M., Puhse, U., & Holsboer-Trachsler, E. (2009). High exercise
levels are related to favorable sleep patterns and psychological functioning in adolescents: A
comparison of athletes and controls. Journal of Adolescent Health. 46(2010), 133-141. doi:
10.1016/j.jadohealth.2009.06.018
Digdon, N. L. (2007). Circadian preference and college student beliefs about how to cope with
sleepiness. Biological Rhythm Research, 39(5), 417-426. doi: 10.1080/09291010701590067
Doherty, M., & Smith, P. M. (2004). Effects of caffeine ingestion on rating of perceived exertion during
and after exercise: A meta-analysis. Scandinavian Journal of Medicine & Science in Sports.
15(2004), 69-78. doi: 10.1111/j.1600-0838.2005.00445.x
Harris, K. M. (2009). Caffeine consumption as a predictor of sleep quality, sleep hygiene, subjective
sleepiness, and academic performance among north texas female college students. Retrieved f
rom Texas Woman's University Dissertations. (T2009 h313c)
Sin, C., W., M., Ho, J., S., C., & Chung, J., W., Y. (2008). Systematic review on the effectiveness of
caffeine abstinence on the quality of sleep. Journal of Clinical Nursing, 18, 13-21. doi:
10.1111/j.1365- 2702.2008.02375.x

15. The Relationship Between Exercise, Sleep Patterns, and Caffeine Consumption 15
Figure 1
Exercise Routine is Positively Associated With School Night Sleep Pattern (N=14)
Note: Outlying score of 25 hours of exercise per week has been omitted. Significant difference at the .05
level

16. The Relationship Between Exercise, Sleep Patterns, and Caffeine Consumption 16
Figure 2
School Week Caffeine Consumption is Negatively Associated With School Night Sleep Pattern (N=14)
Significant difference at the .05 level