Confounding by socioeconomic position remains after adjusting for neighbourhood deprivation: an example using smoking and mortality
- Department of Public Health, Wellington School of Medicine and Health Sciences, University of Otago, Wellington, New Zealand
- Correspondence to: Dr T Blakely Department of Public Health, Wellington School of Medicine and Health Sciences, University of Otago, PO Box 7343, Wellington, New Zealand; tblakelywnmeds.ac.nz
- Accepted 28 April 2004
Area based measures of socioeconomic deprivation are often used as proxies for personal socioeconomic position. But sometimes people of high socioeconomic position live in deprived areas, and vice versa.1,2 This means that adjusting for area deprivation (only) may leave residual confounding for any exposure-outcome association in which socioeconomic position is strongly implicated.3 The purpose of this paper is to report an example in which residual confounding by personal socioeconomic position remains after adjusting for neighbourhood deprivation. We are not aware of previous empirical findings. More generally, we also examine the issue of residual confounding by socioeconomic position when adjusting for just one individual socioeconomic factor (education or income) compared with adjusting simultaneously for a large range of socioeconomic factors. Our empirical example is the association of tobacco with adult mortality in a large study that includes multiple measures of personal socioeconomic position.
METHODS AND RESULTS
We used a New Zealand census mortality cohort of 758 367 men and 798 828 women aged 25 to 74 years at the 1996 census followed up for mortality for three years to compare mortality in current and never smokers (see http://www.wnmeds.ac.nz/nzcms-info.html for details). We used a New Zealand specific measure of neighbourhood socioeconomic deprivation, constructed using proportions of people at the 1996 census with/in: no …
