Association of socioeconomic status with functional capacity, heart rate recovery, and all-cause mortality.
BACKGROUND
Lower socioeconomic status (SES) confers heightened cardiovascular risk and mortality, although the mediating pathways are unclear.


OBJECTIVE
To evaluate the extent to which exercise physiologic characteristics account for the association between lower SES and mortality.


METHODS
Prospective cohort study of 30 043 consecutive patients living in 7 counties in northeast Ohio referred between 1990 and 2002 for symptom-limited stress testing for evaluation of known or suspected coronary artery disease. Follow-up for mortality continued through February 2004.


METHODS
Estimated functional capacity in metabolic equivalents and heart rate recovery, physiologic characteristics that are determined directly from exercise; testing and all-cause mortality during a median follow-up of 6.5 years.


RESULTS
Multivariable models adjusting for demographics, insurance status, smoking status, and clinical confounders demonstrated a strong association between a composite SES score based on census block data and functional capacity (adjusted odds ratio comparing 25th with 75th percentile values, 1.72; 95% confidence interval [CI], 1.56-1.89; P<.001) as well as heart rate recovery (adjusted odds ratio comparing 25th with 75th percentile values, 1.18; 95% CI, 1.07-1.30; P<.001). There were 2174 deaths, with mortality risk increasing from 5% to 10% as SES decreased by quartile (P<.001). Cox proportional hazards models that included all confounding variables except exercise physiologic characteristics demonstrated increased mortality as SES decreased (adjusted hazard ratio comparing 25th with 75th percentile values, 1.32; 95% CI, 1.22-1.42; P<.001). After further adding functional capacity and heart rate recovery, the magnitude of this relationship was reduced (comparing 25th with 75th percentile values; adjusted hazard ratio, 1.17; 95% CI, 1.08-1.26; P<.001), with these variables explaining 47% of the association.


CONCLUSIONS
Impaired functional capacity and abnormal heart rate recovery were strongly associated with lower SES and accounted for a major proportion of the correlation between SES and mortality. Efforts to modify these clinical features among patients with low SES may narrow disparities in mortality.
Shishehbor
Mehdi H
MH
Department of Cardiovascular Medicine, The Cleveland Clinic, Cleveland, Ohio 44195, USA.
Litaker
David
D
Pothier
Claire E
CE
Lauer
Michael S
MS
D000328:Adult; D000368:Aged; D002318:Cardiovascular Diseases / Q000453:epidemiology*; D002320:Cardiovascular Physiological Phenomena; D015331:Cohort Studies; D005080:Exercise Test; D005260:Female; D006339:Heart Rate; D006801:Humans; D016015:Logistic Models; D008297:Male; D008875:Middle Aged; D009026:Mortality; D009820:Ohio; D012959:Socioeconomic Factors