Elsevier

Annals of Epidemiology

Volume 8, Issue 6, August 1998, Pages 384-392
Annals of Epidemiology

Original Reports
Are Sleep Complaints an Independent Risk Factor for Myocardial Infarction?

https://doi.org/10.1016/S1047-2797(97)00238-XGet rights and content

Abstract

PURPOSE: To investigate whether subjective sleep complaints are an independent predictor of myocardial infarction (MI) in a community of older adults and to gain clues as to why the association between sleep complaints and incident MI exists.

METHODS: Using longitudinal data from the Piedmont study on 2960 adults aged 65 or older who were free of symptomatic heart disease at baseline, we screened 19 potential confounders to determine if any, alone or in combination, could explain the observed relationship between incident MI and sleep complaints.

RESULTS: During the three-year follow-up period, there were 152 incident MIs. Restless sleep (incidence density ratio (IDR) = 1.58, 95% confidence interval (CI) = 1.11, 2.24) and trouble falling asleep (IDR = 1.68, 95% CI = 1.09, 2.60) predicted incident MI after adjusting for age, gender, and race. IDRs were not substantially impacted by controlling for smoking, blood pressure, diabetes or obesity. After adjustment for education, number of prescription medicines, self-rated health, and depression score, all IDRs were nullified. In particular, self-rated health and depression were strong independent risk factors for MI.

CONCLUSIONS: A subjective sleep complaint increases the likelihood of a first MI in older adults without overt coronary heart disease (CHD) independently of classic coronary risk factors and appears to be a marker for a syndrome of depression and malaise that may have a causal relationship to MI.

Introduction

Investigations in the 1980s and 1990s indicated that sleep complaints are associated with incident myocardial infarction (MI) and other coronary endpoints 1, 2, 3, 4, 5, 6, 7, 8, 9, 10. However, it is unclear what causes this association. It may be due to common demographic, physical, and psychosocial correlates. Both MI and insomnia are associated with diabetes 11, 12, 13, smoking (14), obesity 11, 15, lower socioeconomic status 16, 17, 18, 19, widowhood 20, 21, 22, 23, depression 17, 24, 25, 26, and lack of social support 23, 27. There may also be causal connections between the two conditions: Prescription heart medications such as beta-blockers may interfere with restful sleep (28), and “sleep” medications, such as tricyclic antidepressants, may have harmful effects on the heart (29).

In this paper, we report on the association between various sleep complaints and incident MI in a group of community elders. To our knowledge, no one has previously done so, although the prevalence of insomniac complaints increases with age and is estimated to be 20–35% for those over 65 years of age 30, 31. Polysomnographic analysis correlates with these subjective complaints and indicates a substantial reduction in the amount of deep non-REM sleep in otherwise healthy older versus younger adults 32, 33.

We examined the effects of several correlates on the sleep complaint-MI association. We did so for two reasons: 1) to determine whether the sleep complaint is an independent predictor of MI, which warrants increased clinical scrutiny and should be routinely included in future studies of MI; and 2) to gain clues as to why the association exists.

Because the covariates were measured at the same time as sleep complaints we cannot differentiate between a confounder and an intervening variable. However, these investigations may provide useful information and are an important first step in directing future research.

We examined both atherosclerotic and psychosomatic risk factors for MI. If the insomnia-MI association is explained by the former, then this could indicate that sleep complaints are a symptom of, or a marker for a known risk factor of atherosclerosis. If instead, the association is explained by psychosocial variables, this result would supplement continuing research on psychosomatic causes of heart disease and may indicate a potentially useful marker: it may be easier to “measure” a sleep complaint than to measure a multi-faceted construct such as social support.

As low socioeconomic status (SES) is associated with both coronary heart disease (CHD) 18, 19 and insomnia 16, 17, we also examined education and income as potential confounders. Finally, we chose to examine a global self-rated health assessment, a powerful predictor of mortality, to determine if sleep dysfunction could provide predictive information for MI in addition to that already provided by this covariate. Intuitively, self-rated health covers psychosocial as well as physical health and is also a very strong correlate of insomnia 34, 35.

Section snippets

Study Population

The Piedmont Health Survey is one of four studies comprising the Established Populations for Epidemiological Studies of the Elderly (EPESE). Begun in 1984, it has followed 4162 of 5221 (80%) eligible persons aged 65 years and over residing in north-central North Carolina. Sampling details are described elsewhere (36).

After a baseline household interview, follow-up contacts were made annually. Nonfatal MI status was determined at the baseline visit by the question: “Has a doctor ever told you

Results

The study population is described in Table 1. The participants ranged in age from 65–101 years (mean = 73 years). One-third were male and more than half were African-American. Less than half had a high school education, and at least two thirds reported an annual income of less than $10,000. However, 60% still considered themselves to be in good or excellent health, and only 10% answered affirmatively to seven or more of 19 items indicative of depression. Prevalence of coronary risk factors was

Discussion

This study found an association between sleep complaints and incident MI events in participants aged 65 to 101 years who were relatively free of symptomatic CHD at baseline. IDRs ranged from 1.15 to 1.68 after adjusting for age, gender, and race. All sleep complaints were associated with elevated risks except “trouble with waking during the night.”

The increased risk of MI with sleep complaints was nullified after adjusting for education, self-rated health, number of prescription medicines, and

Acknowledgements

The research upon which this publication was based was performed pursuant to Contract Number N01-AG-1–2102 with the National Institute on Aging, in support of the Established Populations for Epidemiologic Studies of the Elderly (Duke University, Durham, NC). The content of this publication does not necessarily reflect the views or policies of the U.S. Department of Health and Human Services.

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