Perceptualand MoiorSkillr, 1992, 75, 1168-1170.
O Perceptual and Motor Skills 1992
CHANGES IN THE SELF-REPORTED CONSISTENCY OF NORMAL HABITUAL SLEEP DURATION OF COLLEGE STUDENTS (1978 AND 1992) ' ROBERT A. FIICKS, CRYSTAL JOHNSON, AND ROBERT J. PELLEGRINI San lose State Universily Strmmary.-Changes in the consistency of self-reported sleep habits within two large samples of 763 and 782 college students were assessed for 1978 and 1992. Noteworthy changes over the 14-yr. period included significant decreases in the percentage of students who claimed stable ( 25-year) sleep-duration habits and the percentage reporting satisfaction with their sleep.
Recently, we reported that college students had reduced their median sleep duration from 7.75 hours in 1969 to 6.75 hours in 1989 (Hicks & Pellegrini, 1991) and that the percentage of students who acknowledged sleep problems had risen from 24.4% in 1978 to 53.4% in 1988 (Hicks, Mistry, Lucero, Lee, & Pellegrini, 1989). Collectively, these studies document a sharp decline over the past two decades in both the quantity and the qual~tyof the sleep of college students and underscore the need for research designed to elaborate the reasons for these trends. In this regard, earlier (Hicks, Pellegrini, Hawkins, & Moore, 1978) we presented evidence which vahdated speculation by Webb and Friel (1971) and Hartmann, Baekeland, and Zw&ng (1972) that shortened sleep among college students is a relatively recent change in habitual sleep duration that is probably adopted to meet the increased demands associated with a college education. In this study, to define our sample, we first obtained the responses of 1109 college students to these questions: "How long do you sleep each night," "How consistent is this pattern of sleep," "How long have you been sleeping this number of hours," and "How satisfied are you with your sleep?" Then we eliminated from consideration any individual who either had experienced their reported duration of sleep for less than a 1-yr. period, reported variable durations, or expressed dissatisfaction with their sleep. The resulting sample of 763 students (i.e., 68.8% of the original sample) was made up of satisfied sleepers who had established fairly consistent sleep requirements. From the self-reports of these students, the following contingency table for years of consistency by nightly sleep duration was formed. The differences between the distributions summarized in Table 1 were significant (X42 = 84.6, p < 0.001, with 6 = .33). Our purpose here was to replicate this study and, in so doing, to mea'In part t h s research was supported by NIH-MBRS Grant GM 08192-13. Requests for reprints should be addressed to Robert A. Hicks, Department of Psychology, San Jose State University, San Jose, CA 95192-0189.
1169
CONSISTENCY OF HABITUAL SLEEP DURATION
sure any changes in the consistency of the nightly sleep-duration habits of college students that might have occurred during the 14-year period that had elapsed since the data for our 1978 study were collected. To do this, we obtained the responses of 782 college students to a questionnaire that included the critical items from our 1978 study. After imposing the selection criteria used in the 1978 study, the resulting sample was made up of 331 students, i.e, 42.3% of the original sample. From the selfreports of these students, the following contingency table for years of consistency by nightly sleep duration was formed. As was the case in our 1978 study, the differences between these distributions was significant (X42 = 14.46, p c 0 . 0 1 , with 9 = .21). In comparing the data presented in Tables 1 and 2, we observed that the pattern we noted in 1978, i.e., that short-sleep habits tend to be more recently acquired, had not changed in our 1992 sample. Specifically, when we tested differences between samples of 1978 and 1992, distributions for the 1- to 5-year and 5 + -year sleep-duration subgroups were not significant, i.e., for the 1- to 5-year distribution xe2= 8.28 and for the 5 + -year distribution X42 = 5.10. However, we also noted that the number of individuals who reported longstanding sleep habits had declined significantly from 1978 to 1992. In 1978 the majority (55%) of the students in our sample reported sleep-duration habits that had been stable for at least five years, while in 1992 only 39% of those sampled reported consistent sleep-duration habits for at least the last 5 years. This change is significant, i.e., X L 2 = 23.86, p
O Perceptual and Motor Skills 1992
CHANGES IN THE SELF-REPORTED CONSISTENCY OF NORMAL HABITUAL SLEEP DURATION OF COLLEGE STUDENTS (1978 AND 1992) ' ROBERT A. FIICKS, CRYSTAL JOHNSON, AND ROBERT J. PELLEGRINI San lose State Universily Strmmary.-Changes in the consistency of self-reported sleep habits within two large samples of 763 and 782 college students were assessed for 1978 and 1992. Noteworthy changes over the 14-yr. period included significant decreases in the percentage of students who claimed stable ( 25-year) sleep-duration habits and the percentage reporting satisfaction with their sleep.
Recently, we reported that college students had reduced their median sleep duration from 7.75 hours in 1969 to 6.75 hours in 1989 (Hicks & Pellegrini, 1991) and that the percentage of students who acknowledged sleep problems had risen from 24.4% in 1978 to 53.4% in 1988 (Hicks, Mistry, Lucero, Lee, & Pellegrini, 1989). Collectively, these studies document a sharp decline over the past two decades in both the quantity and the qual~tyof the sleep of college students and underscore the need for research designed to elaborate the reasons for these trends. In this regard, earlier (Hicks, Pellegrini, Hawkins, & Moore, 1978) we presented evidence which vahdated speculation by Webb and Friel (1971) and Hartmann, Baekeland, and Zw&ng (1972) that shortened sleep among college students is a relatively recent change in habitual sleep duration that is probably adopted to meet the increased demands associated with a college education. In this study, to define our sample, we first obtained the responses of 1109 college students to these questions: "How long do you sleep each night," "How consistent is this pattern of sleep," "How long have you been sleeping this number of hours," and "How satisfied are you with your sleep?" Then we eliminated from consideration any individual who either had experienced their reported duration of sleep for less than a 1-yr. period, reported variable durations, or expressed dissatisfaction with their sleep. The resulting sample of 763 students (i.e., 68.8% of the original sample) was made up of satisfied sleepers who had established fairly consistent sleep requirements. From the self-reports of these students, the following contingency table for years of consistency by nightly sleep duration was formed. The differences between the distributions summarized in Table 1 were significant (X42 = 84.6, p < 0.001, with 6 = .33). Our purpose here was to replicate this study and, in so doing, to mea'In part t h s research was supported by NIH-MBRS Grant GM 08192-13. Requests for reprints should be addressed to Robert A. Hicks, Department of Psychology, San Jose State University, San Jose, CA 95192-0189.
1169
CONSISTENCY OF HABITUAL SLEEP DURATION
sure any changes in the consistency of the nightly sleep-duration habits of college students that might have occurred during the 14-year period that had elapsed since the data for our 1978 study were collected. To do this, we obtained the responses of 782 college students to a questionnaire that included the critical items from our 1978 study. After imposing the selection criteria used in the 1978 study, the resulting sample was made up of 331 students, i.e, 42.3% of the original sample. From the selfreports of these students, the following contingency table for years of consistency by nightly sleep duration was formed. As was the case in our 1978 study, the differences between these distributions was significant (X42 = 14.46, p c 0 . 0 1 , with 9 = .21). In comparing the data presented in Tables 1 and 2, we observed that the pattern we noted in 1978, i.e., that short-sleep habits tend to be more recently acquired, had not changed in our 1992 sample. Specifically, when we tested differences between samples of 1978 and 1992, distributions for the 1- to 5-year and 5 + -year sleep-duration subgroups were not significant, i.e., for the 1- to 5-year distribution xe2= 8.28 and for the 5 + -year distribution X42 = 5.10. However, we also noted that the number of individuals who reported longstanding sleep habits had declined significantly from 1978 to 1992. In 1978 the majority (55%) of the students in our sample reported sleep-duration habits that had been stable for at least five years, while in 1992 only 39% of those sampled reported consistent sleep-duration habits for at least the last 5 years. This change is significant, i.e., X L 2 = 23.86, p
