Social position and mortality from respiratory diseases in males and females.

Although social differences in respiratory diseases are considerable, few studies have focused on this disease entity using mortality as an outcome. Does mortality from respiratory disease, including chronic obstructive pulmonary disease (COPD) differ with social position measured by education, income, housing and employment grade? The study population consisted of 26,392 males and females from pooling of two population studies in the Copenhagen area. Data was linked with information from social registers in Statistics Denmark. The relationship between socioeconomic factors and risk of death from respiratory disease and COPD was assessed with an average duration of follow-up of 12 yrs. Education was strongly associated with respiratory mortality in both sexes. The association was stronger in later birth cohorts comparing the highest level of education (>11 yrs) with the lowest (<8 yrs). Although smoking rates were inversely associated with the level of education, the social gradient was not affected by adjustment for smoking. In males, but not in females, there was an additional effect of other indicators of social position, i.e. employment grade (white collar versus blue collar), household income, housing conditions (less than one person per room versus more), and cohabitation (cohabiting versus living alone). Similar results were found for mortality from COPD. The results confirm the existence of a strong social gradient in respiratory mortality and chronic obstructive pulmonary disease, which is independent of smoking and is stronger in males. Social disadvantage is a potentially avoidable cause of death from respiratory disease and further research is needed to explain the excess risk in the socioeconomically disadvantaged.