HS201: Day/Time
Polls have illustrated that there may be a correlation between sleep duration, sleep quality (level of sleep disturbance) and levels of stress (American Psychological Association, 2012; National Sleep Foundation, 2009). Self-reporting of sleep and stress levels may indicate trends, but this relationship needs to be established by utilizing proper scientific methodology so that relationships can be quantified. In this study, the relationship between sleep and stress will be explored using students in HS201.
STEP 1: Hypothesis Generation
It is hypothesized that amongst students of HS201, levels of stress will be negatively correlated with both sleep duration and sleep score. The independent variable is the stress score and the dependent variables are sleep duration and sleep score.
STEP 2: Data Collection
Data for this study was collected from students of HS201 via Moodle survey. All values are self-reported. Sleep was measured not only by duration (length of a typical night sleep), but also by a survey of sleep habits. This survey involved true/false questions regarding different behaviors regarding sleep and tiredness experienced by the student during a typical day. Stress levels were ascertained by having the participant indicate what stressors they have had in their life over the past 12 months. Each stressor was assigned a point value and all points were then combined to a stress score.
STEP 3: Results
The number of students from HS201 that participated in the study was 435, with 144 being male and 291 being female. The participants ranged from Freshmen to Seniors (with three declared as other). The mean number of work hours per week per student was 16.9 hours (s.d. 13.9). The number of semester credits enrolled per student was a mean of 14.6 credit hours (s.d. of 4.4). The mean GPA of students participating in this study was 3.2 (s.d. 0.6).
The r-value for the relationship between stress score and sleep score was 0.12905 with a p-value of 0.007 making this a significant positive correlation between these two variables (as stress score increases, sleep score increases). The higher the level of stress the higher the sleep score. The r-value for the relationship between stress score and sleep duration was -0.02272 with a p-value of 0.6366 which was not significant, indicating no direct correlation between stress score and sleep duration. The r-value for sleep score and sleep duration was -0.26088 with a p-value of 0.0001 which was a significant negative correlation (as sleep score increases, sleep duration decreases).
Based on the results of this study, the data suggests that the higher the stress score the higher the sleep score and the higher the sleep score, the lower the sleep duration. No significant relationship was seen between the stress score and sleep duration. The study represented a good sample size for statistical analysis and it targeted a very specific demographic population which strengthened the results of the study. Conversely, this study was based on self-reporting, which is often problematic in ascertaining true relationships between variables. Surveys are fraught with inherent biases and are subjective. Crafting a good survey vehicle is of paramount importance when completing survey studies. Controlled studies are the second step after completing an initial survey study to be less subjective.
STEP 4: Exploring the Research Literature
Part A
Vgontzas, A. N., Lin, H-M, Papaliaga, M., Calhoun, S., Calhoun, S., Vela-Bueno, A., Chrousos, G. P. & Bixler, E. O. (2008). Short sleep duration and obesity: the role of emotional stress and sleep disturbances. International Journal of Obesity, 32,801-809.
In a study conducted by Vgontzas (2008), the relationship between short sleep duration and obesity was examined. This study included a random sample of 1300 middle-aged men and women from Central Pennsylvania (aged 20 years or older). The mean age for men was 50.8±12.6 years and for women, the mean age was 54.9±13.6 years. The mean BMI for men was 28.8 ±4.3 and for women 32.7±7.5.
Sleep was operationalized by evaluating the participants in the sleep laboratory for one night (8 hours) using 16-channel polygraphs, measurement of respiration and hemoglobin oxygen saturation. Sleep duration was calculated as the percentage of sleep time in both the laboratory as well as self-reporting of how many hours a participant usually slept at night. Stress was operationalized by using the Minnesota Multiphasic Personality Inventory (MMPI-2). BMI was calculated using the height and weight of a participant during their physical examination.
In the association of self-reported sleep duration in relation to stress and BMI, the study revealed that both stress score (MMPI-2) and BMI were significant predictors of the resulting sleep duration of the participant after correcting for age, smoking and sleep-disordered breathing. The MMPI-2 score had a more dramatic reduction in sleep duration than BMI. In fact, the negative association between BMI and sleep duration was only significant for men participating in the study. In the final regression, a 1 s.d. increase of MMPI-2 (stress) resulted in a decrease of 0.7% of sleep time (ST) (p<0.05). A 1 s.d. increase of BMI resulted in a decrease of 0.6% (3 minutes) of ST (p<0.1).
Part B – Article 1
Rowshan Ravan, A. R., Bengtsson, C., Lissner, L., Lapidus, L. & Bjorkelund, C. (2010). Thirty-six-year secular trends in sleep duration and sleep satisfaction, and associations with mental stress and socioeconomic factors – results of the Population Study of Women in Gothenburg, Sweden. Journal of Sleep Research, 19,496-503.
Abstract
Several European studies have reported sleeping problems in 20–40% of the population. We used data from the Population Study of Women in Gothenburg, based on medical examinations of three different representative cohorts of 38- and 50-year-old women in 1968–1969, 1980–1981 and 2004–2005 to study secular trends in sleep-related factors. The average reported sleep duration declined by about 15 min in the 38-year-old women during the 36 years of observation. No corresponding change in sleep duration was observed among 50-year-old women. During the same period, the proportion of women complaining of sleeping problems almost doubled in both age groups: from 17.7% in 1968 to 31.7% in 2004 in 38-year-old women, and from 21.6% to 41.8% in 50-year-old women. The prevalence of insomnia was higher in 50-year olds than in 38-year olds in all investigated cohorts. The use of sleeping medications remained unchanged since 1968. There were significant associations between perceived sleeping problems and reported lower satisfaction concerning economic, social and family situations, as well as with medical retirement and mental stress. There was, however, no association between alcohol consumption and sleeping problems. Regular leisure time physical activity was not, in most cases, associated with less perceived sleeping problems. Our study indicates that the physician should take socio-economic and family situations into consideration when examining female patients complaining of sleeping problems. Improvements on society level rather than on the individual level could be expected to be more efficient in improving women’s sleep.
In a study done by Rowshan Ravan et al. (2010), sleep duration and sleep satisfaction was measured over a 36-year period using medical examination data from the Population Study of Women in Gothenburg in cohorts of 38- and 50-year old women. The data was collected in 1968-1969, 1980-1981 and 2004-2005. The number of women varied in each collection period but ranged between 207-348 women per age group.
Data on sleep duration, sleep quality, sleep problems, mental stress, and economic, social and home situations were collected during medical examinations. The Gothenburg Quality of Life Instrument (GQOLI) was used to evaluate sleep quality and the economic, social and home situations. All other data was collected via questionnaire in the medical examination.
The study revealed that there was a significant correlation between stress and poor sleep quality associated with socioeconomic, social and family situations. Evaluation of sleep quality using the GQOLI showed a significant worsening of sleep quality and duration in the 38-year old cohort between study periods of 1980-1981 and 2004-2005 (p<0.004), but no significant change in the 50-year old cohort. This study highlights the importance of societal stress on the sleep duration and sleep quality. It also demonstrates the necessity to repeat these studies as societial stressors evolve.
Part B – Article 2
Patel, S. R., Blackwell, T., Redline, S., Ancoli-Israel, A., Cauley, J. A., Hillier, T. A., Lewis, C. E., Orwoll, E. S., Stefanick, M. L., Taylor, B. C., Yaffe, K. & Stone, K. L. (2008). The association between sleep duration and obesity in older adults. International Journal of Obesity, 32,1825-1834.
Abstract
Background: Reduced sleep has been reported to predict obesity in children and young adults. However, studies based on self-report have been unable to identify an association in older populations. In this study, the cross-sectional associations between sleep duration measured objectively and measures of weight and body composition were assessed in two cohorts of older adults.
Methods: Wrist actigraphy was performed for a mean (s.d.) of 5.2 (0.9) nights in 3055 men (age: 67–96 years) participating in the Osteoporotic Fractures in Men Study (MrOS) and 4.1 (0.8) nights in 3052 women (age: 70–99 years) participating in the Study of Osteoporotic Fractures (SOF). A subgroup of 2862 men and 455 women also underwent polysomnography to measure sleep apnea severity.
Results: Compared to those sleeping an average of 7–8 h per night, and after adjusting for multiple risk factors and medical conditions, a sleep duration of less than 5 h was associated with a body mass index (BMI) that was on average 2.5 kg/m2 (95% confidence interval (CI): 2.0–2.9) greater in men and 1.8 kg/m2 (95% CI: 1.1–2.4) greater in women. The odds of obesity (BMI X30 kg/m2) was 3.7-fold greater (95% CI: 2.7–5.0) in men and 2.3-fold greater in women (95% CI: 1.6–3.1) who slept less than 5 h. Short sleep was also associated with central body fat distribution and increased percent body fat. These associations persisted after adjusting for sleep apnea, insomnia and daytime sleepiness.
In a study done by Patel et al. (2008), sleep duration was measured in 3055 men and 3052 women to ascertain if there is a relationship between weight and body composition and sleep duration in older adults. The mean age for men was 76.4 years and for women the mean age was 83.6 years.
Average nightly sleep duration was measured using a wrist actigraphy. Sleep diaries were also kept by the participants. BMI and other body measurements were taken in either the home or clinic visits. The participants also completed questionnaires including questions on health status, alcohol and caffeine use, smoking, activity level, presence of depression and use of antidepressants and sleep disorders.
Although stress was not directly measured in this study, there were significant correlations between BMI and sleep duration (p<0.0001 for men and p<0.001 for women) and depression and sleep duration (only significant in women p<0.05).
STEP 5: Conclusion
The subjects in these studies were older than the participants in our class study. There are obviously different stressors depending on age group, so it is prudent to consider the difference in age when comparing these studies. In addition, the rate of obesity in the participants in our study were not measured, but that may have had an influence on the results of the class survey statistics.
In the study of the students of HS201, it was all self-reported data collected via Moodle survey. This was similar to the method used in the Rowshan Ravan et al. (2010) study, although far more metrics were employed in that study with much larger population sizes and over a long period of time (36 years). In the Vgontzas et al. (2008) and Patel et al. (2008) studies the data collected was less subjective because actual physical measurements were taken in a medical setting or sleep laboratory.
There seems to be a consensus between all of the studies that obesity and stress have a significant impact on sleep duration and sleep quality. In some studies, metrics were used to measure stress (GQOLI and MMPI-2) and in others, surveys were constructed to ascertain stress levels. It is apparent that there are many factors influencing sleep duration and quality after examining multiple studies. These studies all agree that there is a correlation between stress and sleep duration and quality. There appears to be differences between age groups and differences over time. In addition, obesity (or high BMI) is correlated with sleep duration and quality in these studies as well.
With respect to the relationship of stress to sleep quality and duration, Mezick et al. (2009) highlighted that stressful life events led to greater variability in sleep duration and more fragmentation of sleep leading to poorer sleep quality. High norepinephrine levels when experiencing negative emotions also pointed to a physiological basis for this phenomena not just a psychological one.
In a study conducted by Hicks & Garcia (1986), university students kept diaries of stress levels and sleep duration. They found that under higher levels of stress, sleep duration was reduced by a standard deviation, whereas when the stress lessened, the average sleep duration increased by a half a standard deviation. This study only utilized 30 students over a four month period, but it was an important study in quantifying the relationship between stress and sleep duration. It particularly noted that stress levels change and individuals all respond to stress differently and that needs to be considered when conducting these types of studies.
Cappuccio et al. (2008) considered the relationship of short sleep duration and levels of obesity. This study was a meta-analysis collecting literature data included 30,002 children and 604,509 adults worldwide. In both groups, there was a significant relationship between short sleep duration and obesity (p<0.0001, both children and adults). This is not necessarily an independent relationship between sleep duration and obesity because it has been shown that stress levels tend to be higher in obese individuals (Vgontzas et al. 2008).
Overall, the studies considered here indicate that there is a significant correlation between stress, obesity and sleep quality and duration. There are a myriad of factors influencing sleep habits, both psychological and physiological. Factors such as socioeconomic status, family genetics, culture, age, education, job satisfaction, etc. no doubt have a direct or indirect influence as well.
References
Cappuccio, F. P., Taggard, F. M., Kandala, N. B., Currie, A., Peile, E., Stranges, S. & Miller, M. A. (2008). Meta-analysis of short sleep duration and obesity in children and adults. Sleep, 31,5:619-626.
Hicks, R. A. & Garcia, E. R. (1986). Level of stress and sleep duration. Perceptual and Motor Skills, 64,44-46.
Mezick, E. J., Matthews, K. A., Hall, M., Kamarck, T. W., Buysse, D. J., Owens, J. F. & Reis, S. E. (2009). Intra-individual variability in sleep duration and fragmentation: associations with stress. Psychoneuroendrocrinology, 34,1346-1354.
Patel, S. R., Blackwell, T., Redline, S., Ancoli-Israel, A., Cauley, J. A., Hillier, T. A., Lewis, C. E., Orwoll, E. S., Stefanick, M. L., Taylor, B. C., Yaffe, K. & Stone, K. L. (2008). The association between sleep duration and obesity in older adults. International Journal of Obesity, 32,1825-1834.
Rowshan Ravan, A. R., Bengtsson, C., Lissner, L., Lapidus, L. & Bjorkelund, C. (2010). Thirty-six-year secular trends in sleep duration and sleep satisfaction, and associations with mental stress and socioeconomic factors – results of the Population Study of Women in Gothenburg, Sweden. Journal of Sleep Research, 19,496-503.
Vgontzas, A. N., Lin, H-M, Papaliaga, M., Calhoun, S., Calhoun, S., Vela-Bueno, A., Chrousos, G. P. & Bixler, E. O. (2008). Short sleep duration and obesity: the role of emotional stress and sleep disturbances. International Journal of Obesity, 32,801-809.
