Insomnia was associated with increased risk of recurrent cardiovascular events in coronary heart disease patients
Authors: Frojd L , Dammen T , Munkhaugen J , Weedon-Fekjaer H , Nordhus IH , Papageorgiou C , Sverre E 
Published: May 2022

Abstract

Funding Acknowledgements
Type of funding sources: None.

Background
Insomnia is highly prevalent in coronary heart disease (CHD) patients. However, the potential effect of insomnia on the risk of recurrent major adverse cardiovascular events (MACE) remains uncertain.

Purpose
To estimate the prospective association of insomnia and the risk of recurrent MACE in a CHD population from routine clinical practice.

Methods
This prospective cohort study included 1082 consecutive patients 2-36 (mean 16) months after a myocardial infarction and/or a coronary revascularization procedure. Data on insomnia, coronary risk factors and comorbidity were collected at baseline. Insomnia was assessed by Bergen insomnia scale (BIS), based on sleep symptoms per week during the past three months. BIS is constructed from the clinical diagnostic criteria for primary insomnia in DSM-IV TR. The primary composite endpoint of MACE defined as cardiovascular death, hospitalization due to myocardial infarction, revascularization, stroke or heart failure was obtained from the hospital records on average 4.2 (SD 0.3) years after the baseline study. Data were analysed using Cox proportional hazard regression on a multiple imputated dataset stratified by prior coronary events.

Results
At baseline, mean age was 62 (range 31-80) years, 21% were females, 90% were revascularized, 47% had participated in cardiac rehabilitation and the prescription rate of antiplatelets (97%) and statins (93%) were high. A total of 364 MACE (21%, 95% CI 19%-24%) occurred in 225 patients, including 39 CV deaths. Almost half of the patients (45%) suffered from insomnia at baseline and 24% used sleep medication the past week. For insomnia, the relative risk (RR) of recurrent MACE was 1.62 (95% confidence interval (CI) 1.24-2.11, p-value&lt;0.001) in age and gender adjusted analysis, 1.49 (95% CI 1.14, 1.97, p-value=0.004) in analysis also adjusted for coronary risk factors and 1.48 (95% CI 1.12, 1.96, p-value=0.006) in a multi-adjusted analysis including age, gender, coronary risk factors and cardiovascular comorbidity. When also adjusted for symptoms of anxiety and depression the RR of insomnia on recurrent MACE remained significant at 1.41 (95% CI 1.05, 1.89, p-value=0.023). Insomnia accounted for 16% of the MACE in attributable risk fraction analyses, being third in importance after smoking (27%) and low physical activity (21%). Obstructive sleep apnea (Berlin Questionnaire) was not associated with recurrent MACE.

Conclusions
Insomnia was associated with increased risk of recurrent MACE in this prospective cohort following CHD patients from routine clinical practice. The association remained significant even after adjustments for the major coronary risk factors, comorbidity and symptoms of anxiety and depression, indicating that the effects of insomnia is not mediated through poor risk factor control and other psychosocial factors alone. These results emphasize the importance of identifying patients with insomnia as part of coronary rehabilitation.