The combined association of psychological distress and socioeconomic status with all-cause mortality: a national cohort study.

This paper was accepted for publication in the journal JAMA Internal Medicine and the definitive published version is available at: http://dx.doi.org/10.1001/2013.jamainternmed.951Background Psychological distress and low socioeconomic status (SES) are recognized risk factors for mortality. The aim of this study was to test whether lower SES amplifies the effect of psychological distress on all-cause mortality.\ud
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Methods We selected 66 518 participants from the Health Survey for England who were 35 years or older, free of cancer and cardiovascular disease at baseline, and living in private households in England from 1994 to 2004. Selection used stratified random sampling, and participants were linked prospectively to mortality records from the Office of National Statistics (mean follow-up, 8.2 years). Psychological distress was measured using the 12-item General Health Questionnaire, and SES was indexed by occupational class.\ud
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Results The crude incidence rate of death was 14.49 (95% CI, 14.17-14.81) per 1000 person-years. After adjustment for age and sex, psychological distress and low SES category were associated with increased mortality rates. In a stratified analysis, the association of psychological distress with mortality differed with SES (likelihood ratio test–adjusted P < .001), with the strongest associations being observed in the lowest SES categories.\ud
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Conclusions The detrimental effect of psychological distress on mortality is amplified by low SES category. People in higher SES categories have lower mortality rates even when they report high levels of psychological distress.\ud
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Psychological distress is becoming recognized increasingly as a risk factor for mortality and a trigger for cardiovascular disease (CVD) events.1- 3 Socioeconomic status (SES) is also a recognized determinant of health status: in developed countries, lower SES levels signal worse health. Even in the most affluent countries, people in lower SES levels have considerably shorter life expectancies and more disease than people in higher SES levels,4- 6 and low SES levels are associated with a high risk for CVD and death in developed countries, such as England.7\ud
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People in higher SES categories may have greater economic, social, and psychological resources and better coping strategies for dealing with adversity.8 These assets may be acquired through learning or better access to resources. Consequently, when both risk factors are present (high levels of psychological distress and low SES levels), we can argue that the resulting effect on mortality is not the mere sum of the two (additive effect) but that some extra risk may appear (multiplicative effect). We therefore hypothesized that SES can operate as an amplifier of psychological distress and that the effect of psychological distress on mortality would be greater in groups with lower compared with higher SES levels. As a consequence, vulnerable populations of adults may be more susceptible to the detrimental effects of psychological distress and may have unmet health care needs.\ud
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Identifying people who are more vulnerable to the health consequences of psychological distress may have clinical and public health implications. For example, questionnaires such as the 12-item General Health Questionnaire (GHQ-12) could be of value in systematic screening by family physicians with the aim of improving the recognition rate of common mental disorders and thereby reducing the risk for CVD and other fatal conditions. We sought to analyze the association of psychological distress and low SES levels on the incidence of all-cause mortality, with an emphasis on the interaction between both risk factors