Effect of Eating out on Quality and Quantity of Sleep among Japanese in Their 20s

Abstract

The purpose of this study was to analyze the effects of eating out or skipping meals on the quality or quantity of sleep in young Japanese adults. We analyzed 584 eligible subjects (283 men and 301 women) aged 20 - 29 years. Information on diet and individual lifestyle characteristics, including sleep quality, which was assessed by the Pittsburgh Sleep Quality Index Japanese version (PSQI-J), were obtained by participants completing an online questionnaire. Kendall’s tau coefficient was used to measure the ordinal association between diet and sleep quality. The Mann-Whitney U test was performed to evaluate differences in sleep quality by frequency of eating out and frequency of skipping meals. The results revealed a significant difference in sleep duration and PSQI-J score between people who eat out >2 times a week (“high restaurants group”) and those who do not (“low restaurants group”). Furthermore, whereas the mean sleep duration in the “high restaurants group” was 6.59 hours, the mean sleep duration in the “low restaurants group” was 6.90 hours (p = 0.007). The PSQI-J score was significantly higher in the “high restaurants group” than in the “low restaurants group” (4.91 versus 4.37, p = 0.006). Significant differences were also evident in the test’s component scores: C2, C3, and C7. No significant difference was found in sleep duration and PSQI-J score between the groups in terms of frequency of skipping meals (breakfast, lunch, and dinner). Our results suggested that excessive intake by eating out more than twice a week may lead to short sleep duration and high PSQI-J score.