Megan Brooks

June 10, 2015

SEATTLE ― The combination of insomnia with short sleep duration raises the risk for cardiovascular disease (CVD), suggesting it represents a more deleterious insomnia phenotype, researchers say.

Insomnia with short sleep duration may be a "modifiable risk factor" for CVD, Suzanne Bertisch, MD, MPH, from Beth Israel Deaconess Medical Center, Boston, Massachusetts, reported in an oral presentation here at SLEEP 2015: Annual Meeting of the Associated Professional Sleep Societies.

Insomnia with objective short sleep duration has been associated with increased risk for the development of hypertension and diabetes and for mortality. In this study, Dr Bertisch and colleagues set out to quantify the association between insomnia symptoms with objective short sleep duration and incident CVD using data from the Sleep Heart Health Study, a community-based prospective longitudinal cohort study.

At baseline between 1994 and 1998, participants completed sleep questionnaires and underwent at-home polysomnography. Those free of CVD at baseline were followed for a median of 11.5 years until first nonfatal or fatal CVD event (including myocardial infarction, revascularization procedure, or stroke), death, or date of last contact (May 2011).

The primary exposure was insomnia with objective short sleep duration, defined as self-reported difficulty falling asleep, getting back to sleep, early morning awakenings, or use of a sleeping pill for 16 to 30 nights per month; and total sleep time of <6 hours on polysomnography.

High-Risk Insomnia Subgroup

Among 4465 participants (mean age, 63.3 years; 56% women), 14% reported insomnia, and 48% of these individuals had objective short sleep duration. During follow-up, a total of 821 CVD events occurred.

In an unadjusted Cox proportional hazard model, people with insomnia and objective short sleep duration had a 46% higher risk for incident CVD compared with a control group. After adjustment for age, sex, race, smoking, apnea hypopnea index, and use of antidepressant medications, the CVD risk with insomnia and short sleep duration was attenuated but remained significant, Dr Bertisch reported.

"At 5 years, the insomnia with objective short sleep duration group had a 7.9% probability of having cardiovascular event compared with 6.7% in the reference group. At 10 years, their probability was 15.3% compared to 13.2% in the reference group, and at 13 years, they had a 20.1% probability compared to 17.4%," Dr Bertisch reported.

Table. Incident CVD Risk With Insomnia and Short Sleep Duration

Group Unadjusted HR (95% CI) Age-Adjusted HR Fully Adjusted HR
Insomnia with short sleep duration 1.46 (1.14 - 1.85) 1.24 (0.98 - 1.58) 1.27 (1.02 - 1.62)

CI, confidence interval.

 

"When a patient has a 20% risk of having a cardiovascular event, they are considered to be in the highest risk category, and the recommendations are they get maximal preventive treatment to lower their risk of cardiovascular disease," she noted.

Neither insomnia alone nor short sleep duration alone conferred increased risk for CVD.

The fact that objective short sleep duration was determined by one-night polysomnography is a limitation of the study. Also, the duration of insomnia symptoms was not captured, and the researchers were unable to assess time-varying covariates (eg, hypertension) or change in insomnia status over time.

Despite these limitations, the results provide evidence that insomnia with objective short sleep duration confers elevated risk for incident CVD. "The risk appears to be increased by about 2.5% over a 13-year period and appears to be independent of traditional cardiovascular disease risk factors," Dr Bertisch said.

Future work is needed to elucidate mechanisms linking insomnia with short sleep duration to CVD, she added.

"Nice Replication"

In an interview with Medscape Medical News, Philip Gehrman, PhD, CBSM, of the Department of Psychiatry, University of Pennsylvania, Philadelphia, and member of the Penn Sleep Center, said, "Other large epidemiologic studies have shown that in people with insomnia, the ones with objective short duration seem to do worse across several outcomes — moreso than people who have short sleep duration but without insomnia."

"This particular pattern of insomnia, with short sleep duration, has been linked to higher rates of mortality, cardiovascular outcomes, metabolic outcomes, and neurocognitive outcomes, so this study is not necessarily new, but it is nice replication of findings from other cohorts," Dr Gehrman explained.

The study had no commercial funding. The authors and Dr Gehrman have disclosed no relevant financial relationships.

SLEEP 2015: Annual Meeting of the Associated Professional Sleep Societies: Abstract 0610. Presented June 8, 2015.

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