Large-scale data from wearables reveal regional disparities in sleep patterns that persist across age and sex (original) (raw)

Prior reports on geographical differences in sleep duration have relied on samples collected at different time points with a variety of subjective instruments. Using sleep data from a total of 553,559 nights from 23,680 Fitbit users (aged 15-80y), we found objective evidence for regional disparities in sleep duration of 32-43 min between Oceanian and East Asian users on weekdays. This was primarily driven by later bedtimes in east Asians. Although users in all countries extended sleep on weekends, east Asians continued to sleep less than their oceanian counterparts. Women generally slept more than men, and older users slept less than younger users. Reasons for shorter sleep duration in east Asians on both weekdays and weekends, across the lifespan and in both sexes remain to be investigated. Voluntary sleep restriction is a global epidemic, with widespread consequences on health, safety and productivity. Short sleepers (<7 h/night) present a 12% greater risk of all-cause mortality compared to those sleeping 7 to 8 h per night 1. Furthermore, econometric modeling has showed that for five countries in the Organisation for Economic Cooperation and Development (OECD) losses of up to $680 billion a year can be attributed to insufficient sleep 2. Striking geographical differences in the extent of sleep loss have been documented in questionnaire-based studies 3-5. East Asians sleep less and go to bed later than their Western counterparts 3-6 , likely due to longer working hours, intense pressure to excel, and an "always-connected" culture prevalent in Asia. In addition, these disparities in sleep duration appear to differ by age and sex. South Korean 12 th-graders have been reported to average just 4.9 h of sleep a night 7 , compared to their peers in Australia who sleep 8.5 h (males) and 9.1 h (females) 8. This discrepancy, while still present, was almost halved in older adults >65y, with studies reporting a mean of 6.5 h in South Korea 9 and 8.3 h in Australia 10. Prior reports comparing countries are predominantly based on comparisons of single country studies that were collected using a variety of subjective instruments and time windows instead of head-to-head comparisons using objective instruments. As such there is merit in establishing the implied geographical differences in sleep duration using large scale actigraphy. Self-report measures, while easily scalable, can be unreliable 11 , being subject to rounding errors and recall bias, as well as instrument-related differences. For example, data collected from single-question surveys demonstrate poor agreement (within ± 2.5 h) with data collected using 24 h time-use surveys 12. The influx of inexpensive, consumer-based activity trackers in this era of big data present an unprecedented opportunity to objectively characterize sleep habits on a global level. In 2017 alone, worldwide wearable device shipments reached a 115 million units 2. These trackers would also allow for the standardized collection of data from populations with limited reporting ability, for example in young children, older adults, or clinical populations, and across different language groups. In the present study, we analyzed large-scale sleep data from Fitbit users in five countries located within two geographical regions: Oceania (Australia and New Zealand) and East Asia (Singapore, Hong Kong and South Korea), in order to quantify crosscountry differences in objective sleep patterns. These regions include countries typically at either end of the sleep duration spectrum 4. We also investigated whether these disparities in sleep patterns differed by age group and sex. In addition, as weekday and weekend sleep patterns typically differ 5,6,13 , we conducted separate analyses for both day types, as well as for weekday-weekend sleep extension.