In a recent study published in Scientific Reports, researchers investigated the relationship between sleep-wake changes and depressive symptoms among midlife women.
Their results demonstrate that women who experience long-term severe sleep-wake changes may face an increased risk of experiencing depressive symptoms, highlighting the importance of maintaining stable sleep patterns to mitigate mental health risks.
Study: Sleep–wake changes and incident depressive symptoms in midlife women. Image Credit: Pixel-Shot/Shutterstock.com
Background
Changes to sleep-wake patterns have been linked to the development of metabolic, cardiovascular, neurodegenerative, and psychiatric disorders. Maintaining stable sleep-wake rhythms is crucial for mental well-being, as irregularities are associated with an increased risk of depression.
Previous studies have shown that disturbances to circadian rhythms, such as irregular night shifts or later sleep midpoints, correlate with an increased risk of depression. However, these studies often rely on single assessments of sleep schedules. For this reason, little is known about the possible long-term impacts.
During menopause, women experience more sleep disturbances and depressive symptoms, potentially due to fluctuating ovarian hormones. Despite this, research rarely considers hormone levels and menopausal status in examining sleep-wake rhythms and depression.
About the study
This study explored the relationship between long-term changes in sleep-wake rhythms and depression risk in menopausal women, using sleep midpoint—a stable measure of circadian rhythm—as a key indicator.
Data were drawn from a long-term, multi-ethnic study of midlife women in the U.S. Initiated between 1996 and 1997; it included 3,302 premenopausal women between the ages 42 and 52, who met criteria such as regular menstruation, an intact uterus, and no recent hormone use.
Women were followed close to yearly so that the transition through menopause could be monitored.
The analysis included women who participated in sleep surveys during the third (1999-2001) and fourth (2000-2002) visits, but not those with insufficient sleep data, baseline depressive symptoms, or those undergoing certain medical treatments.
Participants reported sleep habits, including bedtime, wake time, sleep duration, and quality. The sleep midpoint was calculated by adding half of the sleep duration to the time to fall asleep.
Changes in sleep midpoint over a year were categorized as mild (<1 hour), moderate (1-2 hours), or severe (>2 hours). Insomnia symptoms and other sleep problems were also recorded.
Symptoms of depression were measured using the 20-item scale, where scores ≥16 indicated significant symptoms.
Data on race/ethnicity, education, physical activity, health status, dietary intake, and various health indicators such as body mass index, blood pressure, and hormone levels were also collected.
The researchers used statistical tests such as the Chi-square test and Wilcoxon rank-sum test to look at differences in symptoms of depression across the factors measured.
They then calculated hazard ratios to examine how the risk of developing depressive symptoms changed when the sleep midpoint varied.
Findings
The study followed 1,579 midlife women with an average age of 49 across different racial and ethnic groups, over a median of 7 years.
Researchers found that 81.6% of the women in the study group experienced mild changes in their sleep midpoint, while 12.1% experienced severe changes. During the study, 496 women developed depressive symptoms, translating to an incidence rate of 61 for every 1,000 person-years.
Women who developed symptoms of depression tended to be younger and less educated; they also had lower family income and physical activity levels. This group reported lower sleep quality and was more likely to experience frequent night sweats and symptoms of insomnia.
The study identified a significant association between greater changes in sleep midpoint and increased risk of depressive symptoms.
After researchers adjusted the analysis for age, race/ethnicity, lifestyle, and health factors, women with severe changes in sleep midpoint had a 51% higher risk of developing depressive symptoms compared to those with mild changes.
This association remained significant and increased to 57% after adjusting sex hormones and menopausal status.
Conclusions
This study found that larger changes in sleep-wake patterns significantly increase the risk of developing depressive symptoms in midlife women, supporting the theory that sleep instability during menopause is a key risk factor.
Women with severe changes in sleep midpoint were 57% more likely to develop depressive symptoms compared to those with mild changes, independent of other risk factors.
This study's strength lies in its longitudinal design, capturing long-term shifts in sleep patterns.
Unlike previous research, which assessed sleep midpoint at a single time point, this study tracked changes over consecutive years, providing a more detailed picture of changes to sleep-wake rhythms.
However, the study has limitations, including reliance on self-reported sleep data, which may be less accurate than objective measures like polysomnography. The findings are specific to women in the menopausal transition, and additional research is needed to determine if they apply to other populations.
Future research should explore the mechanisms underlying these associations, considering factors such as melatonin, cortisol, and genetic influences.
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