Relationship Between Insoluble Dietary Fiber Intake and Non-Restorative Sleep in Japanese Adults: A Cross-Sectional...

Non-restorative sleep (NRS)-a subjective feeling of unrefreshing/insufficient rest despite adequate sleep duration-an important sleep-quality indicator is associated with depression and mortality. We examined whether insoluble dietary fiber intake is associated with NRS in Japanese adults, after adjusting for socioeconomic, lifestyle, and dietary factors.

Using cross-sectional data from 5034 adult (≥20 years) respondents of the National Health and Nutrition Surveys (2014 and 2018), Japan, self-assessed NRS (coded as 1, absence as 0) was analyzed with insoluble fiber intake (g/1000 kcal) modeled as a continuous variable; logistic regression analyses with progressive adjustments included Model 1, adjusted for sex, age, and body mass index; Model 2, comprising socioeconomic and lifestyle factors; Model 3, adjusted for sleep duration; and Model 4, which included dietary energy, protein, fat, vitamin D, and magnesium.

Among 19.3% of participants with NRS, the median (interquartile range) insoluble dietary fiber intake was 5.45 (4.10-6.97) g/1000 kcal, with higher NRS prevalence among younger adults (<60 years), non-drinkers (no habitual alcohol consumption), and individuals with short sleep (<6 h). Higher insoluble dietary fiber intake was consistently associated with a lower NRS likelihood, before and after adjustment for potential confounders. In the fully adjusted model, younger age (<60 years), no habitual alcohol consumption, and short sleep (<6 h) were independently associated with greater odds of NRS.

Higher insoluble dietary fiber density correlated with lower odds of NRS, indicating a significant association, rather than causation, that warrants longitudinal clarification of the temporal relationship between dietary fiber intake and perceived sleep restorativeness.