Insomnia an important risk factor for MACE

Patients with coronary heart disease (CHD) may have an increased risk of major adverse cardiovascular (CV) events (MACE)* if they also have insomnia, suggested a study presented at the ESC Preventive Cardiology 2022 annual congress.

“Sleep problems are linked to mental health issues, but our study found that insomnia was still significantly associated with heart events even after accounting for symptoms of anxiety and depression,” said study lead author Lars Frojd, a medical student at the University of Oslo, Oslo, Norway.

“The findings suggest that heart patients should be assessed for insomnia and offered appropriate management,” Frojd pointed out.

A total of 1,082 consecutive adults aged 18–80 years (mean age 62 years, 21 percent female) were recruited for this prospective study 2–36 months (mean 16 months) following a myocardial infarction (MI) and/or coronary revascularization. The six-question Bergen Insomnia Scale (BIS) questionnaire was used to identify self-reported clinical insomnia including the ability to fall asleep and stay asleep, premature waking, feeling inadequately rested, tiredness during the day that affects the ability to function at work or socially, and dissatisfaction with sleep.

Ninety percent of patients had undergone revascularization and 47 percent had undergone cardiac rehabilitation. Use of antiplatelet therapy and statins, based on prescription data, was high at 97 and 93 percent, respectively.

At baseline, 45 percent of patients had insomnia (mean BIS sum score 13.9), with 24 percent reporting use of medication for sleep in the past week. Patients were followed up for a mean 4.2 years (mean 5.7 years after index event), during which time 21 percent of patients (n=225) experienced 364 MACE, which included 39 CV deaths.

After adjustment for multiple factors including age, gender, coronary risk factors, and CV comorbidity, insomnia was tied to an increased risk of recurrent MACE (hazard ratio [HR], 1.48, 95 percent confidence interval [CI], 1.12–1.96; p=0.006). [ESC Preventive Cardiology 2022, Rapid Fire Abstracts Session 1 – Secondary Prevention and Rehabilitation; Sleep Advances 2022;3:1-10]

Further adjustment for symptoms of anxiety and depression did not affect the statistical significance of the association (HR, 1.41, 95 percent CI, 1.05–1.89; p=0.023).

In age- and gender-adjusted analysis, there was no association between a risk of obstructive sleep apnoea (OSA), as per the Berlin Questionnaire, and MACE (HR, 1.22; p=0.170). However, OSA could still be a potential confounding factor in the insomnia–MACE association, the authors said.

In attributable risk fraction analysis, insomnia was the third most important contributing factor for recurrent MACE at 16 percent, following smoking and low physical activity (27 and 21 percent, respectively).

“This means that 16 percent of recurrent MACE might have been avoided if none of the participants had insomnia,” noted Frojd. “This is indeed an interesting finding as large efforts are made to change risk behaviours such as smoking and low physical activity, whereas insomnia is hardly attended to or screened for among patients with CHD in clinical practice,” said the authors.

While the relative risk of MACE with insomnia reduced following adjustment for CV risk factors, the mechanisms behind the insomnia–MACE association are still unknown, said Frojd and co-authors. “CV risk factors are to some extent involved in the relationship between clinical insomnia and future MACE. However, it is uncertain at this stage whether the CV risk factors act as confounders, mediators, or both,” they added.

“Our study indicates that insomnia is common in heart disease patients and is linked with subsequent CV problems regardless of risk factors, co-existing health conditions, and symptoms of mental health,” Frojd continued. “Further research is needed to examine whether insomnia treatments such as cognitive behavioural therapy and digital applications are effective in this patient group.”

The authors also highlighted that BIS sum score was not associated with elevated MACE risk after adjusting for anxiety and depression. “This emphasizes the importance of clinical insomnia symptoms, in terms of diagnostic criteria for insomnia, for the prognosis in patients with CHD,” the authors said.