A new study suggests that the amount of time a person spends in REM sleep is tied to their general level of anxiety, and that this relationship plays out differently depending on their sex and age.
Researchers in Spain recruited 128 healthy adults aged 18 to 82, tracked their sleep with consumer wearables, and measured their trait anxiety a stable personality characteristic reflecting how prone someone is to feeling anxious. They found that people with higher trait anxiety spent a larger share of the night in REM sleep and less in light sleep, while deep sleep appeared unrelated to anxiety levels. Women in the study scored higher on both anxiety and REM proportion than men, and older adults showed the opposite pattern lower anxiety and lower REM sleep compared with younger participants.
The findings, published in the Journal of Sleep Research, add to a growing body of evidence linking REM sleep to emotional regulation and raise questions about how normal variations in sleep architecture relate to mental health in the general population.
What they found
All 128 participants wore a Fitbit Charge 5 for one week at home to capture their sleep stages. Anxiety was assessed with the Spielberger State-Trait Anxiety Inventory (STAI-T), a widely used questionnaire that measures how anxious a person feels in daily life rather than just in the moment. To validate the wearable data, the team also ran a small substudy comparing Fitbit readings against polysomnography, the gold standard for sleep measurement, in six participants. The trends matched prior validation studies, the authors reported.
Across the full sample, trait anxiety correlated positively with REM sleep proportion (r = 0.34, p < 0.005) and negatively with light sleep (r = -0.20, p = 0.02). Deep sleep showed no significant association. The correlation means that as anxiety scores rose, REM occupied a greater fraction of total sleep time, while light sleep correspondingly shrank.
Sex differences were pronounced. Women had significantly higher STAI-T scores than men (mean 24.3 vs. 18.7, t(126) = 3.86, p < 0.005) and also spent a greater percentage of their sleep in REM (t(126) = 2.65, p = 0.01). The researchers suggest that hormonal and neurobiological factors could contribute to both patterns.
Age also played a role. Adults aged 50 and older reported lower trait anxiety than those under 50 (t(126) = 3.79, p < 0.005) and showed reduced REM sleep proportions (t(126) = 4.27, p < 0.005). Sleep-related anxiety, measured with a separate scale called DSEA-S, was elevated in older men but remained stable across age groups in women, hinting at a sex-specific divergence in how worry about sleep itself changes over the lifespan.
Why it matters
REM sleep has long been considered important for emotional processing. Animal and human studies suggest that during REM, the brain reconsolidates emotional memories, reducing their affective charge. The new findings align with that framework: if people with higher trait anxiety have more REM sleep, it could reflect a compensatory mechanism the brain recruiting extra REM time to cope with a higher emotional load.
The study also demonstrates that consumer wearables like the Fitbit Charge 5 can detect meaningful relationships between sleep architecture and psychological traits outside the lab. While not as precise as polysomnography, wearables enable larger and more naturalistic sampling than traditional sleep studies, which are expensive and typically limited to a single night in a lab.
The sex and age differences add nuance. If women have both higher anxiety and higher REM, the anxiety-REM link may not be uniform across populations. And the finding that older adults have lower anxiety and less REM raises the possibility that age-related reductions in REM are part of normal brain changes rather than a risk factor.
Limits
The study is correlational, so directionality cannot be determined. It is equally possible that higher REM sleep predisposes someone to anxiety, that anxiety drives REM changes, or that a third factor such as stress or genetics influences both.
The sample, while reasonably sized, was predominantly female (75 women vs. 53 men) and drawn from a non-clinical population. Results may not generalize to people with clinical anxiety disorders or to more diverse demographic groups.
The wearable validation substudy included only six participants. Although the authors note the trends matched published validation data, the small sample limits confidence in the absolute accuracy of the sleep stage classification for every individual.
Bottom line
Higher trait anxiety is associated with more REM sleep and less light sleep in healthy adults, but the relationship is shaped by sex and age. Women tend toward higher anxiety and more REM, while older adults show lower anxiety and less REM. The findings support the use of consumer wearables for studying sleep-psychology connections at scale, but causal interpretations remain premature.
Source
Title: REM Sleep Correlates of Trait Anxiety in Non-Clinical Adults: The Role of Sex and Age
Authors: Mar Mediano, Enrique G. Fernandez-Abascal, Sabela Fondevila Estevez
Journal: Journal of Sleep Research, Vol. 35, Issue 4, e70318, August 2026 (First published: 19 February 2026)
DOI: 10.1111/jsr.70318