Title, Date of Publication & Journal

Insomnia and the risk of incident heart failure: a population study

Wednesday March 6^th 2013

European Heart Journal

Claim supported by evidence?

This paper provides evidence for an association between insomnia and subsequent heart failure, but does not establish a causal link.

Summary

• This is a large observational study carried out to examine whether insomnia is linked to an increased risk of heart failure among adults.
• It was part of a large cohort study being carried out in Norway to look at a number of different health outcomes.
• Self-reported insomnia symptoms were measured at baseline and heart failure was ascertained from linked hospital records and a national death registry.

Study Conclusions

The main conclusion is that insomnia symptoms are associated with an increased risk of heart failure.

There was no clear evidence that the individual insomnia symptoms were associated with an increased risk of heart failure; however, there was an increased risk of heart failure as the number of insomnia symptoms increased (up to a maximum of three symptoms – difficulty initiating sleep almost every night, difficulty maintaining sleep almost every night, and having non-restorative sleep more than once a week).

The authors acknowledge that they cannot determine whether the association is causal.

Strengths/Limitations

This was a large prospective study.

The authors have adjusted for a large number of potential confounding factors, although they do acknowledge that they did not adjust for sleep apnoea, an established risk factor for cardiovascular disease.

The authors also carried out sensitivity analyses which showed that their results remained similar after, for example, restricting to heart failure occurring at least 5 years after the start of the study and restricting to hospital-confirmed cases of heart failure.

The authors acknowledge that, by using hospital and death records, there may have been some misclassification in terms of heart failure. However, this is unlikely to have had a major impact on the results.

It is acknowledged that that this study cannot establish a causal link between insomnia and heart failure.

The authors do not discuss the possibility that insomnia and heart failure might be associated because they share a common cause.