Increase in eveningness and insufficient sleep among adults in population-based cross-sections from 2007 to 2017

Short or long sleep duration, insufficient sleep, and Evening chronotype associate with many health issues and increased risk for mortality. Understanding population-level changes in sleep and chronotype frequencies is important for assessing the prospective health status of the society and future challenges on health care at a national level. This study examines the cross-sectional differences in sleep duration, insufficient sleep, and chronotype frequencies indicated by both circadian preference and habitual sleep-wake rhythm among adults living in Finland during a 10-year period of 2007-2017.

The study sample (N = 18 039) was derived from he National FINRISK 2007 and 2012 Studies, and The FinHealth 2017 Study, each consisting of a random sample of adults, aged 25-74 years and as stratified by age and sex, and providing the self-reported data on their circadian preference, habitual daily sleep duration, insufficient sleep and bedtimes.

During the 10 years, sleep duration decreased, insufficient sleep increased and circadian preference towards eveningness increased significantly in each 10-year age group and among both sexes. In general, eveningness was more common among younger adults in all the study years but, as compared to 2012, in 2017 bedtimes and midpoint of sleep were more advanced among this age group while sleep-wake rhythm became more delayed in older adults. The decrease in sleep duration and the increase in insufficient sleep were emphasized in younger adults and especially in women, whereas the increase in eveningness in older adults and in men.

The evolution of sleep and chronotype frequencies from 2007 to 2017 is alarming, as these might lead to a poorer health status in the adult population and thus cause more strain to the public health. The mismatch between sleep-wake behavior and circadian preference was emphasized in young adults, indicating a greater risk for circadian misalignment in the Finnish adult population in the future, if there will not be any interventions to correct this mismatch.