Smartwatch Study Links Midlife to Rising Nighttime Awakenings in Women

A large multicountry analysis of Galaxy smartwatch data has found that wakefulness after sleep onset (WASO) rises sharply in women during midlife, with the increase notably steeper than the one seen in men of the same age.¹

3.8 Million Nights of Smartwatch Data Analyzed

The SONAR study (NCT01858532) analyzed roughly 3.8 million nights of sleep data from 192,500 female Galaxy Watch users aged 20 to 65 across the US, South Korea, Germany, France, and the United Kingdom, along with a comparison sample of 145,000 male users. Using linear mixed models adjusted for country, body mass index (BMI), weekday vs weekend nights, and daily activity, researchers examined 3 sleep parameters: total sleep period duration (TSPD), total sleep time (TST), and WASO.

Data were drawn from Samsung Health's consumer database and captured using the Galaxy Watch's accelerometer and photoplethysmography sensors, which prior validation work has shown to have high sensitivity for detecting sleep and high specificity for detecting wake relative to polysomnography. To limit confounding from seasonal effects, all sleep data came from a single month, March 2024, and users needed at least 7 nights of recorded sleep along with self-reported height and weight to be included.

WASO Rises Up to 32% in Women by Their 60s

Compared with women aged 20 to 24 years, WASO increased by an average of 5.4 minutes (15.3%) at ages 50 to 54, 8.8 minutes (24.9%) at ages 55 to 59, and 11.2 minutes (31.7%) at ages 60 to 65. The corresponding increases among men were smaller across all 3 age bands. The steepest jump in women occurred between the 45-to-49 and 50-to-54 age groups, a window that overlaps with the typical menopause transition.

TSPD and TST both declined modestly with age, with TST roughly 13 to 17 minutes shorter among women in their 50s and 60s relative to the youngest group. Country-level differences were also apparent: women in South Korea had shorter TSPD and TST across all ages compared with Western countries, and their WASO began climbing as early as their early 30s, whereas the midlife jump in Western countries appeared later. Weekend nights were associated with meaningfully longer sleep duration, while BMI and physical activity level showed only small associations with WASO specifically.

Findings Align With Prior 11-Million-Night Wearable Study

The authors noted that their findings aligned with an earlier global analysis of more than 11 million nights of wearable data from nearly 70,000 adult nonshift workers across 47 countries, which similarly found that nighttime awakenings increase and sleep duration decreases with age, with distinct patterns by gender.² That earlier study, like SONAR, relied on objective wearable measurements rather than self-report, lending convergent support to the idea that age-related sleep disruption in women is detectable at scale using consumer devices.

The 2021 analysis similarly reported that sleep onset and offset times shift earlier with age, adding a timing dimension to the duration and awakening trends observed in SONAR. Together, the studies span different device types, populations, and geographic footprints, which strengthens confidence that the midlife sleep changes are not an artifact of any single wearable platform or sample.^1,2

Menopause May Drive the Pattern, but Causality Remains Unproven

The study authors pointed to plausible contributing factors beyond aging itself, including hormonal shifts associated with menopause, increased caregiving-related stress, and a higher prevalence of mood symptoms among midlife women, while cautioning that cross-sectional wearable data cannot establish causality.¹ They also note that the Galaxy Watch is not a medical-grade device, that users opting into 7 or more nights of tracking may not represent the general population, and that data on menopausal stage, medication use, and vasomotor symptoms were unavailable.

Even with these caveats, the authors suggested wearable data could give clinicians and patients a practical tool for flagging sleep disruption earlier in the menopause transition, supporting more proactive conversations about symptom management during routine care.

References

1. Soares CN, Dinkel-Keuthage C, Baker FC, et al. Sleep pattern differences in women at midlife: a large-scale multi-country smartwatch study (SONAR). Sleep. Published online July 28, 2026. doi:10.1093/sleep/zsag197
2. Jonasdottir SS, Minor K, Lehmann S. Gender differences in nighttime sleep patterns and variability across the adult lifespan: a global-scale wearables study. Sleep. 2021;44(2):zsaa169. doi:10.1093/sleep/zsaa169