Differences Among the Coloured, White, Black, and Other South African Populations in Smoking-Attributed Mortality at Ages 35–74 Years: A Case-Control Study of 481,640 Deaths
Does mortality related to smoking differ among different ethnic groups in South Africa?
This was case-control study of 481,640 South Africans who were between the ages of 35 and 74 years, and died between 1999 and 2007. Cases were deaths from diseases expected to be affected by smoking; controls were deaths from selected other diseases, excluding only HIV, cirrhosis, unknown causes, external causes, and mental disorders. Additional data collected included information about age, sex, population group, education, smoking 5 years ago (yes or no), and underlying disease. Disease-specific case-control comparisons yielded smoking-associated relative risks (RRs; diluted by combining some ex-smokers with the never-smokers). These RRs, when combined with national mortality rates, yielded smoking-attributed mortality rates. Summation yielded RRs and smoking-attributed numbers for overall mortality.
In the coloured population, smoking prevalence was high in both sexes, and smokers had about 50% higher overall mortality than did otherwise similar nonsmokers or ex-smokers (for men: RR 1.55; 95% confidence interval [CI], 1.43-1.67; and for women: RR, 1.49; 95% CI, 1.38-1.60). The RRs were similar in the white population (for men: RR, 1.37; 95% CI, 1.29-1.46; and for women: RR, 1.51; 95% CI, 1.40-1.62), but was lower among Africans (for men: 1.17; 95% CI, 1.15-1.19; and for women: RR, 1.16; 95% CI, 1.13-1.20). If these associations are largely causal, smoking-attributed proportions for overall male deaths at ages 35-74 years were 27% in the coloured, 14% in the white, and 8% in the African population. For female deaths, these proportions were 17% in the coloured, 12% in the white, and 2% in the African population. Because national mortality rates were also substantially higher in the coloured than in the white population, the hazards from smoking in the coloured population were more than double those in the white population.
The investigators concluded that the highest smoking-attributed mortality rates were in the coloured population and the lowest were in Africans. The substantial hazards already seen among coloured South Africans suggest growing hazards in all populations in Africa where young adults now smoke.
This analysis of South African populations allows for identification of groups at risk for smoking-related deaths. Further study is warranted for other African populations.
Keywords: Case-Control Studies, South Africa, Smoking
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