Sleep Pattern Differences in Women at Midlife: A Large-Scale Multi-Country Smartwatch Study (SONAR)

To evaluate associations between age and objectively measured sleep in women.

We analyzed ~3.8 million nights' data from 192 500 female Galaxy Smartwatch users aged 20-65 years (United States, South Korea, Germany, France, and the UK) with ≥7 nights' sleep data during March 2024. We evaluated associations between age and total sleep period duration (TSPD), total sleep time (TST), and wakefulness after sleep onset (WASO; log-transformed) using linear mixed models, adjusting for repeated user measures, country, body mass index, weekday/weekend night, and daily activity time. Reference group was age 20-24 years. Separate models were run for a comparison group of men.

In women WASO increased notably at midlife; average increases of +5 mins (+15%) for 50-54 years, +9 minutes (+25%) for 55-59 years, and + 11 minutes (+32%) for 60-64 years vs. reference group (corresponding increases in men were + 3 minutes [+9%], +6 minutes [+16%], and + 9 minutes [+27%]). Compared with the reference group, age differences in TSPD and TST were ≤ 5 minutes less and ≤ 17 minutes less, respectively. Effects of age on TST and WASO were similar across Western countries; in South Korea, TSPD and TST were shorter across all ages, while increases in WASO were apparent from early adulthood.

A pronounced increase in WASO was seen in women at midlife. Women in this stage of life could benefit from early identification and tailored interventions to improve their sleep as part of overall health counselling.