Associations of healthy lifestyle and socioeconomic status with mortality and incident cardiovascular disease: two prospective cohort studies
BMJ 2021; 373 doi: https://doi.org/10.1136/bmj.n604 (Published 14 April 2021) Cite this as: BMJ 2021;373:n604
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Dear Editor
Zhang et al. examined the effect of lifestyles on the association between socioeconomic status (SES) and mortality and incident cardiovascular disease (CVD) (1). SES was evaluated by family income, occupation/employment status, education level, and a healthy lifestyle score was constructed using information on smoking, alcohol consumption, physical activity, and dietary quality. Adjusted hazard ratios of subjects with low SES against high SES for all-cause mortality, CVD mortality, and incident CVD significantly increased. In addition, proportions mediated by lifestyle ranged from 5 to 10% for each association. Although unhealthy lifestyles mediated a small proportion of the socioeconomic inequity in health outcomes, healthy lifestyles were associated with lower mortality and CVD risk in different SES subgroups. I have two concerns about their study with special reference to lifestyle factors and ethnic difference.
First, the statistical model for estimating the mortality risk by lifestyle factors can also be acceptable. Li et al. conducted a long-term follow-up study to estimate the impact of lifestyle factors on premature mortality and life expectancy in the US population (2). They selected 5 lifestyle factors as smoking, body mass index, physical activity, alcohol intake, and diet quality. Adjusted hazard ratios (95% confidence intervals) of complete healthy lifestyles for all-cause mortality, cancer mortality, and cardiovascular disease mortality were 0.26 ( 0.22-0.31), 0.35 (0.27-0.45), and 0.18 (0.12-0.26), respectively. They also estimated that expectancy at age 50 years elongated 14.0 years for women and 12.2 years for men by complete healthy lifestyles. I suspect that many factors contribute to mortality risk, and lifestyle factors and SES might be changed by aging. In a long-term follow-up study, time-dependent factors should also be considered for the health risk estimation.
Second, Zhang et al. evaluated the health risk in Western countries, and ethnic difference should be evaluated for the association. Stringhini et al. explored SES differences in overall and cause-specific mortality in the developing country in the African region (3). Occupational position was used as the indicator of SES and lifestyle-related risk factors, smoking, drinking, obesity, diabetes, hypertension, hypercholesterolemia, were assessed. Adjusted HR (95% CI) of participants in the low SES group against the high SES group for overall mortality, CVD mortality, and non-cancer/non-CVD mortality were 1.80 (1.24-2.62), 1.95 (1.04-3.65), and 2.14 (1.10-4.16), respectively. In addition, lifestyle-related risk factors explained a small proportion of the associations between low SES and mortality indicators. There was a consistent result that lifestyle-related risk factors contributed relatively small to the association between SES and mortality regardless of ethnic difference. But caution should be paid that contribution of lifestyle-related risk factors existed. Further prospective studies are needed to conduct a meta-analysis to specify the relationship.
References
1. Zhang YB, Chen C, Pan XF, et al. Associations of healthy lifestyle and socioeconomic status with mortality and incident cardiovascular disease: two prospective cohort studies. BMJ 2021;373:n604.
2. Li Y, Pan A, Wang DD, et al. Impact of healthy lifestyle factors on life expectancies in the US population. Circulation 2018;138(4):345-355.
3. Stringhini S, Rousson V, Viswanathan B, et al. Association of socioeconomic status with overall and cause specific mortality in the Republic of Seychelles: results from a cohort study in the African region. PLoS One 2014;9(7):e102858.
Competing interests: No competing interests
Dear Editor
Poverty of scarcity was a major cause of health inequity in 19th century. [1]. Poverty of plenty, which is associated obesity and unhealthy lifestyle, is the major cause of health inequity in western world now.[2].
Currently, public health relies on nudge theory when trying to persuade individuals to eat healthily and exercise regularly.[3]. An individual focused approach unfortunately does not deal with the fundamental structural causes of health inequity.
So it is not surprising that Zhang et al state that “healthy lifestyle promotion alone might not substantially reduce the socioeconomic inequity in health”. [4].
Public health measures that, historically, made a major impact on population health involved societal level measures. Examples include effective sewage system, clean running water, workplace safety laws and smoking ban. [5]. Public health needs to go back to the basics and deal with inequity at structural level rather than relying on nudge theory to change individual behaviour.
References
1 Parochial Medical Relief. Prov Med Surg J 1840;s1-1:199–203. doi:10.1136/bmj.s1-1.12.199
2 Power C. Health and social inequality in Europe. BMJ 1994;308:1153–6. doi:10.1136/bmj.308.6937.1153
3 Oliver A. Is nudge an effective public health strategy to tackle obesity? Yes. BMJ 2011;342:d2168. doi:10.1136/bmj.d2168
4 Zhang Y-B, Chen C, Pan X-F, et al. Associations of healthy lifestyle and socioeconomic status with mortality and incident cardiovascular disease: two prospective cohort studies. BMJ 2021;373:n604. doi:10.1136/bmj.n604
5 Calman K. The 1848 Public Health Act and its relevance to improving public health in England now. BMJ 1998;317:596–8. doi:10.1136/bmj.317.7158.596
Competing interests: No competing interests
Role of socioeconomic status in mortality from cardiovascular disease in low income countries
Dear Editor,
As pointed out by Zhang et al., Socio-Economic Status (SES) is a risk factor for Cardio-Vascular Diseases (CVD) that merits attention. (1)
Earlier, Materic et al. found that the patients from the lowest income group had more co-morbidities and worse cardiovascular risk factor profile. They were also less likely to undergo coronary angiography and percutaneous coronary intervention. (2) The Prospective Urban Rural Epidemiology study indicated that mortality was the highest in those of low SES in Low-Income Countries (LIC). (3) People from low SES suffer from the lack of awareness of symptoms, less access to ambulances/ diagnostic services and out-of-pocket expenditure. (4) These problems are more prominent in LIC. Patients with low SES stumble on unnecessary delays in reaching the hospital, non-availability of specific care like thrombolysis and coronary revascularization, and poor affordability for medicines. (5) In India, economically progressive states like Delhi, Goa witness less mortality from stroke whereas states in the eastern part of the country with low economic status experience the highest comparative mortality. (6) For ischemic heart disease, mortality in rural India is surpassed that of its urban counterpart. (7)
There is further need for focusing on LIC for understanding the contribution of SES in mortalities from CVD.
References
1. Zhang YB, Chen C, Pan XF, et al. Associations of healthy lifestyle and socioeconomic status with mortality and incident cardiovascular disease: two prospective cohort studies. BMJ 2021;373:n604.
2. Matetic A, Bharadwaj A, Mohamed MO, et al. Socioeconomic Status and Differences in the Management and Outcomes of 6.6 Million US Patients With Acute Myocardial Infarction. Am J Cardiol. 2020;129:10-18.
3. Rosengren A, Smyth A, Rangarajan S, et al. Socioeconomic status and risk of cardiovascular disease in 20 low-income, middle-income and high-income countries: the prospective urban rural epidemiology (PURE) study. Lancet Glob Health. 2019;7:e748–60.
4. Xavier D, Pais P, Devereaux PJ, et al. Treatment and outcomes of acute coronary syndromes in India (CREATE): a prospective analysis of registry data. Lancet. 2008;371:1435–42.
5. Gupta R, Yusuf S. Challenges in management and prevention of ischemic heart disease in low socioeconomic status people in LLMICs. BMC Med. 2019 Nov 26;17:209.
6. Roy MP. Factors associated with stroke mortality in India. Curr Med Issues 2020;18:179-83.
7. Ke C, Gupta R, Xavier D, et al. Divergent trends in ischemic heart disease and stroke mortality in India from 2000 to 2015: a nationally representative mortality survey. Lancet Glob Health. 2018;6:e914–23.
Competing interests: No competing interests