Abstract
Sleep is modulated by several factors, including sex, age, and chronotype. It has been hypothesised that contemporary urban populations are under pressure towards shorter sleep duration and poorer sleep quality. Baependi is a small town in Brazil that provides a window of opportunity to study the influence of sleep patterns in a highly admixed rural population with a conservative lifestyle. We evaluated sleep characteristics, excessive daytime sleepiness, and chronotype using the Pittsburgh Sleep Quality Index, Epworth Sleepiness Scale and Morningness-Eveningness Questionnaire questionnaires, respectively. The sample consisted of 1,334 subjects from the Baependi Heart study (41.5% male; age: 46.5 ± 16.2 y, range: 18–89 years). Average self-reported sleep duration was 07:07 ± 01:31 (bedtime 22:32 ± 01:27, wake up time: 06:17 ± 01:25 hh:min), sleep quality score was 4.9 + 3.2, chronotype was 63.6 ± 10.8 and daytime sleepiness was 7.4 ± 4.8. Despite a shift towards morningness in the population, chronotype remained associated with reported actual sleep timing. Age and sex modulated the ontogeny of sleep and chronotype, increasing age was associated with earlier sleep time and shorter sleep duration. Women slept longer and later, and reported poorer sleep quality than men (p < 0.0001). This study provides indirect evidence in support of the hypothesis that sleep timing was earlier prior to full urbanisation.
Highlights
No access to electricity[13]
Women had poorer self-reported sleep quality than men based on Pittsburgh Sleep Quality Index (PSQI) score (5.4 ± 3.3 vs 4.5 ± 2.9; p < 0.001, Cohen’s d value = 0.18), accounting for a small difference between the sexes
Self-reported sleep duration was longer in women than men (means ±standard deviation (07:13 ± 1:33) vs (06:57 ± 1:27) hour:min ±hour:min; p < 0.01); the difference was small according to the Cohen’s d value of 0.10
Summary
Access to electric light was associated with a reduction of sleep duration in a hunter-gatherer community in Argentina[14]. An objective evaluation of sleep duration in three hunter-gatherer societies found average sleep durations between 5.1 and 7.1 hours[17] These communities showed significant seasonal patterns, and sleep timing was more likely to be associated with environmental temperature rather than with light (sunset or sunlight). We demonstrated a significant shift towards morningness in the frequency distribution of chronotypes in the Baependi Heart Study population This raised the question of whether this diurnal preference was associated with significantly earlier self-reported bedtimes and wake up times (as opposed to self-reported preferred ones). The quantitative answers to PSQI allowed us to consider self-reported rise and bed times
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