Women with Poor Sleep During Midlife at Significantly Elevated Risk for Future CVD
Women aged 40 to 65 years who had persistent insomnia and poor sleep duration were at a 75% greater risk for incident CVD over 2 decades of follow up.
Women who during midlife experience a trajectory of persistent insomnia, alone and in combination with short sleep duration, may be at up to a 75% greater risk of cardiovascular disease (CVD) over the subsequent 2 decades, according to new research published in the Go Red for Women issue of the journal Circulation.
In the study, the association with increased CVD risk remained significant after investigators controlled for the presence of CVD risk factors and other potential sources of disturbed sleep.
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Investigators identified 4 trajectories of insomnia symptoms and 3 related to patters of sleep duration among nearly 3000 participants in the Study of Women’s Health Across the Nation (SWAN) whose sleep was assessed up to 16 times over 22 years. Women with persistently high insomnia and persistently short sleep duration were at significantly higher risk for incident CVD, including myocardial infarction (MI) cerebrovascular accident (CVA), heart failure, or revascularization procedures.
The midlife years, typically considered as ages 40 to 65 years, are a somewhat unstable cardiometabolic period for women. The span includes the menopausal transition and is recognized for the rapid accretion of vascular risks beyond the effect of aging, the investigators wrote. Further, 40% to 50% of women report new sleep problems during this time according to first author Rebecca C Thurston, PhD, Psychiatry, Epidemiology, Psychology, and Clinical and Translational Science, at the University of Pittsburgh and colleagues.
The authors cite evidence of an association between insufficient sleep alone and elevated CVD, exposing women at midlife to the dangerous combination of heightened cardiometabolic risk and the effects of sleep disturbance. Thurston and fellow researchers set out to evaluate the impact of sleep patterns over time on the risk for CVD to expand on existing research they note has been limited by single sleep assessments that cannot account for chronicity of exposure.
SWAN provided data on participants aged 45 to 62 years at baseline from 7 US sites recruited in 1996 and 1997 who participated in annual physical examinations. SWAN participants were either premenopausal or in early perimenopause, were not using oral contraceptives or receiving hormonal therapy and were free of CVD. Over a span of 16 examination visits, participants completed questionnaires on insomnia symptoms, sleep duration, vasomotor symptoms and depression and were queried on CVD events.
Relationships between observed sleep trajectories and incident CVD were derived using Cox proportional hazards models, accounting for factors including age, race, education, and CVD risk factors averaged over visits as well as for additional covariates, ie, vasomotor symptoms, snoring, and depression.
FINDINGS
The final cohort for analysis numbered 2964 participants whose average age at baseline was 46 years; approximately half were White (48%). Baseline sleeping average was 6.55 hours/night and more than 30% reported insomnia symptoms at the baseline visit. Median follow-up was 19.2 years during which researchers recorded 202 fatal or nonfatal CVD events.
Thurston et al identified 4 patterns of insomnia symptoms among participants across 2 decades of midlife: persistent low symptoms (38.5%), moderate symptoms that decreased over time (19.0%%), low symptoms that increased over time (19.9%), and persistently high symptoms (22.6%).
Women who reported persistently high insomnia symptoms had a 1.71 (95% CI, 1.19 – 2.46; P < .01) times higher risk of CVD compared to those with low symptoms over time, according to the study, and the risk persisted after adjusting for ASCVD risk score.
The researchers noted 3 sleep duration trajectories among the women:
- 15% persistently short (~4.85h/night)
- 55.4% persistently moderate (6.39 h/night)
- 30.2% Persistently moderate to long (7.70 h/night)
Women with persistent short sleep had a 1.51 times higher CVD risk.
High insomnia, short sleep duration
When they combined the trajectories of insomnia symptoms and sleep duration, investigators found that women with both persistent high insomnia and short sleep duration were at a 1.75 (95% CI, 1.03 – 2.98; P < .05) times higher risk for CVD. The risk was less but still nearly double among the participants with low, moderate-decreasing, or low-increasing insomnia symptoms + short sleep duration 1.45 (95% CI, 0.84 - 2.50); among the women characterized with high insomnia symptoms + moderate or moderate to long sleep duration, risk for incident CVD increased by 70% (95% CI, 1.06 – 2.72; P < .05).
The significant positive association between insomnia and CVD remained after adjusting for covariates including vasomotor symptoms, snoring, or depression, according to the results.
While previous work has questioned the importance of the combined insomnia-sleep duration phenotype in older women, Thurston and colleagues found the combination doubled the risk of future CVD in the minimally adjusted models and was associated with a 75% increased risk even after multivariable adjustment.
“The current study is the first to characterize sleep over the full span of midlife as well as to include an extended follow-up period to characterize subsequent CVD events,” investigators noted, adding that the longer follow up is essential to understanding this link, “given the older age at which women typically experience their first ASCVD event.
“This study underscores the importance of the chronicity of poor sleep for its implications for CVD risk” and highlights the importance of considering sleep history and patterns when assessing CVD risk in older women.
