Individual-level and neighborhood-level income measures: agreement and association with outcomes in a cardiac disease cohort.
BACKGROUND
Census-based measures of income often are used as proxies for individual-level income. Yet, the validity of such area-based measures relative to 'true' individual-level income has not been fully characterized.


OBJECTIVE
The objectives of this study were (1) to determine whether area-based measures of household income are a suitable proxy for self-reported household income and (2) to assess whether these measures are associated with outcomes in a cardiac disease cohort.


METHODS
We used a prospective cohort from the Alberta Provincial Project for Outcome Assessment in Coronary Heart Disease (APPROACH) cardiac catheterization registry.


METHODS
A total of 4372 patients having undergone cardiac catheterization and who also completed a 1-year follow-up questionnaire on self-reported income level were studied.


METHODS
Our measurements were survival to 2.5 years after catheterization and health-related quality of life (EuroQoL).


RESULTS
Agreement between the 2 income measures generally was poor (unweighted Kappa = 0.07), particularly for the low-income patients. Despite this poor agreement, both income measures were positively associated with survival and EuroQoL scores. An outcome analysis that simultaneously considered individual level income and area-based income revealed that low-income individuals have poorer survival and lower quality of life scores if they live in low income neighborhoods, but not if they live in high income neighborhoods.


CONCLUSIONS
The area-based estimates of household income in these data demonstrate poor agreement with self-reported household income at the level of individual patients, particularly for low-income patients. Despite this, both income measures appear to be prognostically relevant, perhaps because individual and neighborhood income measure different constructs.
Southern
Danielle A
DA
Department of Community Health Sciences, Alberta, Canada.
McLaren
Lindsay
L
Hawe
Penelope
P
Knudtson
Merril L
ML
Ghali
William A
WA
D000416:Alberta / Q000453:epidemiology; D006328:Cardiac Catheterization; D019352:Censuses; D003327:Coronary Disease / Q000401:mortality* / Q000628:therapy; D005260:Female; D006801:Humans; D007182:Income; D008297:Male; D008875:Middle Aged; D017063:Outcome Assessment, Health Care; D011204:Poverty Areas; D011446:Prospective Studies; D011788:Quality of Life; D012042:Registries; D012111:Residence Characteristics; D012650:Self Disclosure; D011795:Surveys and Questionnaires