Age-social stratification designs had a negligible impact on income-mortality associations.
OBJECTIVE
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.


METHODS
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).


CONCLUSIONS
More complex designs incorporating age-social stratification techniques generate similar income-mortality associations as more simplified approaches, which classified SES using absolute income thresholds.
Wijeysundera
H C
HC
Schulich Heart Program, Sunnybrook Health Sciences Centre, University of Toronto, Ontario, Canada.
Austin
P C
PC
Mustard
C A
CA
Chong
A
A
Alter
D A
DA
D000328:Adult; D017677:Age Distribution; D000367:Age Factors; D000368:Aged; D000369:Aged, 80 and over; D015340:Epidemiologic Research Design; D005260:Female; D006306:Health Surveys; D006801:Humans; D007182:Income; D008137:Longitudinal Studies; D008297:Male; D008875:Middle Aged; D009026:Mortality; D009203:Myocardial Infarction / Q000191:economics / Q000401:mortality; D009864:Ontario / Q000453:epidemiology; D011379:Prognosis; D012923:Social Class