Socioeconomic status, functional recovery, and long-term mortality among patients surviving acute myocardial infarction

Abstract

Objectives: To examine the relationship between socio-economic status (SES), functional recovery and long-term mortality following acute myocardial infarction (AMI).

Background: The extent to which SES mortality disparities are explained by differences in functional recovery following AMI is unclear.

Methods: We prospectively examined 1368 patients who survived at least one-year following an index AMI between 1999 and 2003 in Ontario, Canada. Each patient was linked to administrative data and followed over 9.6 years to track mortality. All patients underwent medical chart abstraction and telephone interviews following AMI to identify individual-level SES, clinical factors, processes of care (i.e., use of, and adherence, to evidence-based medications, physician visits, invasive cardiac procedures, referrals to cardiac rehabilitation), as well as changes in psychosocial stressors, quality of life, and self-reported functional capacity.

Results: As compared with their lower SES counterparts, higher SES patients experienced greater functional recovery (1.80 ml/kg/min average increase in peak V02, P<0.001) after adjusting for all baseline clinical factors. Post-AMI functional recovery was the strongest modifiable predictor of long-term mortality (Adjusted HR for each ml/kg/min increase in functional capacity: 0.91; 95% CI: 0.87-0.94, P<0.001) irrespective of SES (P = 0.51 for interaction between SES, functional recovery, and mortality). SES-mortality associations were attenuated by 27% after adjustments for functional recovery, rendering the residual SES-mortality association no longer statistically significant (Adjusted HR: 0.84; 95% CI:0.70-1.00, P = 0.05). The effects of functional recovery on SES-mortality associations were not explained by access inequities to physician specialists or cardiac rehabilitation.

Conclusions: Functional recovery may play an important role in explaining SES-mortality gradients following AMI.

Figure 1. Function recovery according to income tertile among patients referred to cardiac rehabilitation (Figure 1a), not referred to cardiac rehabilitation (Figure 1b), seen by a cardiologist in follow-up (Figure 1), not seen by a cardiologist in follow-up (Figure 1d).

Figure 2. Relationship between functional recovery (i.e., % 1-year changes in self-reported peak VO₂₎ and expected 10-year mortality according to income after risk-adjustment for all remaining factors.