Age–social stratification designs had a negligible impact on income–mortality associations

Wijeysundera, H.C.; Austin, P.C.; Mustard, C.A.; Chong, A.; Alter, D.A.; for the SESAMI study group,

doi:10.1016/j.jclinepi.2006.11.011

« Previous Next »Journal of Clinical Epidemiology
Volume 60, Issue 6 , Pages 579-584, June 2007

Age–social stratification designs had a negligible impact on income–mortality associations

H.C. Wijeysundera
- Schulich Heart Program, Sunnybrook Health Sciences Centre, University of Toronto, Ontario, Canada
P.C. Austin
- The Institute for Clinical Evaluative Sciences, Sunnybrook Health Sciences Centre, University of Toronto, Ontario, Canada
- The Department of Health Policy, Management, and Evaluation, University of Toronto, Canada
C.A. Mustard
- Institute for Work and Health and the Department of Public Health Science, University of Toronto, Canada
A. Chong
- The Institute for Clinical Evaluative Sciences, Sunnybrook Health Sciences Centre, University of Toronto, Ontario, Canada
D.A. Alter
- The Institute for Clinical Evaluative Sciences, Sunnybrook Health Sciences Centre, University of Toronto, Ontario, Canada
- The Department of Health Policy, Management, and Evaluation, University of Toronto, Canada
- Division of Cardiology, Department of Medicine, and The Li Ka Shing Knowledge Institute of St. Michael's Hospital, University of Toronto, Canada
- Corresponding author. Institute for Clinical Evaluative Sciences, Schulich Heart Centre, Sunnybrook Health Sciences Centre, University of Toronto, 2075 Bayview Avenue, G-wing 1-06, Ontario, Canada, M4N 3M5. Tel.: 416-480-5838; fax: 416-480-6048.
for the SESAMI study group

Accepted 14 November 2006. published online 24 March 2007.

Abstract

Objectives

Age–social stratification has been used to offset socioeconomic status (SES) misclassification due to cohort effects. This study was to evaluate whether age–income stratification designs generate comparable income–mortality associations as those whose income rankings are based on absolute thresholds.

Study Design and Setting

Using self-reported income as our SES variable, and mortality as our outcome measure, the impact of age–social stratification was examined in two distinct cohorts: one with acute myocardial infarction (AMI) (n=3,138), and the second free of cardiovascular disease (n=15,115). Age-adjusted income–mortality associations were compared between age–social stratification techniques, which used “age-relative” income thresholds and “absolute” income thresholds whose ranks were independent of patient age.

Results

In both cohorts, crude mortality inversely correlated with age and income. Techniques using “age-relative” income thresholds yielded similar adjusted odds ratio for mortality as did those that used “absolute” income threshold methods (differences in adjusted odds ratios [±95% confidence interval (CI)] between “absolute” and “age-relative” classifications for highest vs. lowest income tertiles: −0.05 [−0.24, 0.12] among patients with AMI and 0.05 [−0.03, 0.13] among patients without cardiovascular disease).

Conclusion

More complex designs incorporating age–social stratification techniques generate similar income–mortality associations as more simplified approaches, which classified SES using absolute income thresholds.

Keywords: Socioeconomic status, Health outcomes, Age stratification, Regression models, Mortality, Acute myocardial infarction