Sleep Midpoint Associated With Depressive Symptoms

A study found that depressive symptoms were associated with a sleep midpoint outside of 2:00-4:00 am.

Sleep midpoints outside of the 2:00-4:00 am period were associated with developing depressive symptoms, according to a cross-sectional study published in Sleep Health. Psychological health domains were also associated with sleep irregularity in older women.

Depression has been linked to the timing and regularity of sleep in older adults, with a healthy sleep schedule having a midpoint of 2:00-4:00 am. The current study aimed to evaluate if poorer psychological health was associated with early or late midpoint of sleep and if poorer psychological well-being, anxiety, and depressive symptoms were associated with irregularity in sleep timing.

The researchers used the SWAN cohort study for participants, who were women aged 42 to 52 years and enrolled in 1996. Women who were menstruating, not pregnant or lactating, and not taking reproductive hormones were eligible for enrollment. Data were collected from 2015 to 2016.

Women in this study performed an actigraphy substudy that excluded any women who were blind, had plans to travel across time zones during the protocol period, or were wheelchair bound. Women were included if they had at least 4 days of useable data, and the final sample had a mean (SD) of 7.7 (0.9) nights of data.

Actigraphy data were collected through a wrist actigraphy that was worn for 7 consecutive days. The researchers collected data on sleep timing and sleep regularity, and participants were tasked with completing 4 well-being scales to assess psychological well-being, with lower composite scores indicating lower psychological well-being.

There were 1197 participants included in the final analytis. The mean age was 65.5 (2.6) years, and all of the participants were post menopausal. Twenty-five percent of participants identified as Black, 46% as White, 12% as Chinese, 11% as Japanese, and 6% as Hispanic. The mean total sleep time was 6 hours, 30 minutes (range, 2 hours, 28 minutes to 9 hours, 48 minutes) and the mean wake after sleep onset was 52 minutes (range, 4-166).

The study found that lower psychological well-being (ß, –0.21) and higher depressive (ß, 1.77) and anxiety (ß, 0.97) symptom scores were associated with greater sleep irregularity, with these associations remaining significant after adjustment for covariates. The depressive symptom severity score increased by 1.36 points, the well-being composite score dropped by 0.18 points, and generalized anxiety symptom severity increased by 0.93 points for every hour of sleep irregularity.

Lower psychological well being (ß, –0.15) and greater depressive symptoms (ß, 1.50) were associated with a sleep midpoint outside of 2:00-4:00 am.

The odds of experiencing depressive (odds oatio [OR], 1.73) and anxiety (OR, 1.53) symptoms were increased by greater sleep irregularity. This association was similar after adjustment for covariates.

Sleep was more irregular in Black participants compared with White, Chinese, and Japanese participants. Hispanic participants had more irregular sleep compared with Japanese participants. Black participants also had a later sleep midpoint compared with White and Japanese participants. There was no association between a sleep midpoint that was outside of the 2:00-4:00 am time period and depressive symptom severity scores for Black women (ß, –1.03). However, White women had an association between a higher depressive severity score and a sleep midpoint outside of 2:00-4:00 am (ß, 1.65).

There were some limitations to this study. Participants self-reported sleep period for actigraphy, and well-being, depression, and anxiety were measured with questionnaires. The study also used actigraphy rather than polysomnograph and also only had female participants, which might make it hard to generalize to other populations.

The researchers concluded that elevated depressive symptoms were linked to a sleep midpoint that is outside of the 2:00-4:00 am period. Well-being, elevated anxiety symptoms, and elevated depressive symptoms were also associated with irregular sleep.


Swanson LM, Hood MM, Hall MH, et al. Sleep timing, sleep regularity, and psychological health in early late life women: findings from the study of women’s health across the nation (SWAN). Sleep Health. Published online December 9, 2022. doi:10.1016/j.sleh.2022.11.001

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