Pmptualond Moto~Skills,1990, 71, 1377-1378. @ Perceptual and Motor Skds 1990
RELATIONSHIP BETWEEN HABITUAL SLEEP DURATION AND DIET ' KRISTY LUCERO AND ROBERT A. HICKS Son Jose State
Summary.-Speculation and indirect evidence have suggested a relationship between habitual sleep duration and food intake. We tested this hypothesis by asking groups of short- and longer-sleeping students to keep 21-day sleep and food-intake diaries. We found no reliable evidence that sleep habits are linked to any major dietary variables as measured in this study and concluded that the differences between our results and those of an earlier study may reflect differences in the methodologies used. I n generalizing from a series of studies in which he observed the behavior of various psyc h i a ~ r ~patlent c groups who were losing or gaining weight, Crisp (1980) speculated that there is a direct relationship between food intake and sleep duration. Further, he also suggested that both sleep quality and duration might be related to the specific components of a person's diet. Although these assertions have, as yet, not been directly tested, in previous studies we have reported results that could be viewed as providing indirect support for Crisp's conclusions. For example, we have demonstrated that as compared to their longer-sleeping peers, habitually short-sleeping college students are more likely to report symptoms of eating disorders (Hicks & Rozette, 1986), disruptions of normal eating patterns (Hicks, McTighe, & Juarez, 19861, concern over excess weight (Hicks & Gaus, 1983), and greater perceived levels of energy, for example, a finding that could suggest an elevated metabolic rate and consequently greater caloric intake requirements (Hicks & Guista, 1982). The purpose of this study was to provide a more direct test of Crisp's hypothesis. This was done by asking groups of habitual shortIM = 6.7 0.5 hr./night) and longer-sleeping (M = 8.2 2.8 hr./night) college students to keep precise food intake and sleep diaries for a 21-day period. To identify the subjects who were asked to volunteer for this study, we first pretested large groups of students enrolled in introductory psychology courses with a questionnaire that asked them to estimate their habitual sleep duration and to rate their over-all satisfaction with their sleep. We identified those students who reported sleeping either 5 6 . 5 or 2 8 . 0 hr. per night, who were satisfied with their sleep, and who had established their current pattern of sleep for at least a 6-mo. period. These students, who were potential subjects for this study, were approached individually, and the demands of the study were explained to them. The students who agreed to volunteer were given instructions on how to keep the comprehensive daily records of their food intake and sleeping that were a required feature of this study. When the diaries were completed, first, daily sleep durations were computed as a check on the subjects' status as either an habitual short- or longer-sleeper. In all, 23 short-sleepers and 20 longer-sleepers completed these diaries for the entire 21-day period. Then, for those students who met the criteria for sleep duration, food intake data were coded for entry into the computer so that the major dietary components could be analyzed using the Nutritionist I11 Program (North, 1985). The results of the analyses of the major dietary components data for each sleep group are listed in Table 1. As can be seen by inspecting the table, none of the t statistics computed to
'This research was supported by NIH-MBRS Grant GM08192-11. Requests for reprints should be sent to Robert A. Hicks, Department of Psychology, San Jose State University, San Jose, CA 95192.
Food Component Variable
K cal consumed % protein consumed % carbohydrates consumed 4b fat consumed
Short-sleepers M .SD 2457 18.5 47.3 34.2
2.7 6.1 5.5
2387 18.4 49.5 32.7
771 4.1 7.3 5.2
.25 .14 -1.08 .94
none of these values are significant.
analyze the differences between these groups of short- and longer-sleepers on each of the dietary components were significant. Thus, our data do not provide support for the hypothesis that sleep duration and food intake are directly related. Perhaps the aferences between our results and inferences that Crisp drew from his data can be traced to the methodologies used. Essentially, Crisp observed the sleep of psychiatric patients who were selected because they were either gaining or losing weight, while we observed the diets of habitually short- and longer-sleepmg college students without regard to current weight changes. Collectively, then, these data suggest that perhaps sleep duration may be modified during periods of weight change but that well-formed sleep-duration habits do not affect food intake. REFERENCES CRISP, A. H. (1980) Sleep, activity, nutrition and mood. British Journal of Psychiatry, 137, 1-7.
HICKS,R. A., & GAUS,W. (1983) Self-reported excess body weight in short- and long-sleeping college students. Psychological Reports, 52, 930. HICKS, R. A., & GUISTA,M. (1982) The energy levels of habitual long and short sleeper;. BulkVin of the Psychonomic Society, 19, 131-132. HICKS, R. A., MCTIGHE,S., & JUAREZ, M. (1986) Sleep duration and eating behaviors of college students. Perceptual and Motor Skills, 62, 25-26. HICKS,R. A., & R O Z E ~E., (1986) Habitual sleep duration and eating disorders in college students. Perceptual and Motor Skills, 62, 209-210. NORTH,L. A. (1985) The N-Squared nutritionist: III. A program for analyzing and creating diets. Silverton, OR: N-Squared Computing.
Accepted December 30, 1990.