Perceived stress and risk of ischemic heart disease: causation or bias?

BACKGROUND: It is unclear whether the commonly recognized link between stress and cardiovascular disease is causal or the result of reporting bias. The objective of this study was to address the association between perceived stress and first incidence of ischemic heart disease and to evaluate the suggested reporting bias by addressing subdiagnoses of ischemic heart disease separately.
METHODS: The 11,839 men and women who participated in the Copenhagen City Heart Study were at baseline (1981-1983) asked about their stress level. The participants were followed in nationwide registries until the year 2000, and fewer than 0.1% were lost to follow-up. During follow-up, 2316 individuals were diagnosed with ischemic heart disease.
RESULTS: High levels of stress were associated with slightly higher risk of incident ischemic heart disease in both women (hazard ratio = 1.23; 95% confidence interval = 1.01-1.51) and men (1.25; 1.00-1.56). When subdiagnoses of ischemic heart disease were analyzed separately, high stress was associated with markedly higher incidence of angina pectoris for women (1.83; 1.15-2.91) and for men (2.14; 1.32-3.47). There was no association with myocardial infarction for women (0.80; 0.56-1.15) or for men (1.09; 0.79-1.52). All associations attenuated with prolonged follow-up.
CONCLUSIONS: It remains uncertain whether perceived stress affects subdiagnoses of ischemic heart disease differently or whether the strong association with angina pectoris was spuriously created by a tendency for stressed individuals to report more cardiovascular symptoms. Future studies on this issue should address subdiagnoses of ischemic heart disease separately and should carefully consider the impact of reporting bias and prolonged follow-up.