Association of neighborhood median income to outcomes in hypertrophic cardiomyopathy

Abstract

Background

Neighborhood median household income (NMHI), a key social determinant of health, is being recognized as a major source of inequity in healthcare. Its impact on patients with hypertrophic cardiomyopathy (HCM) is uncertain.

Objective

We sought to study the association between NMHI and long-term outcomes of HCM patients.

Methods

This was an observation registry of 6368 HCM patients (median age 56 years, 58 % men, 83 % white, 32 % with ≥1 sudden death risk factor) who underwent a clinical evaluation at a tertiary care center between 2002 and 18. NMHI (US$) was calculated from each patient's zip code, using data from the US Census Bureau and Department of Housing & Urban Development. The primary outcome was death, appropriate internal cardioverter defibrillator (ICD) discharge or heart transplant in follow up.

Results

Patients were categorized as obstructive (oHCM, n = 3827 or 60 %, 65 % symptomatic, median NMHI $51,600) and nonobstructive (nHCM, n = 2541 or 40 %, 73 % asymptomatic, median NMHI $53,700) using echocardiography. At a median of 6 years (interquartile range or IQR 2.91, 9.74), there were 998 (16 %) primary events (deaths = 939), with breakdown as follows: 599/3827 (16 %) in oHCM and 399/2541 (16 %) in nHCM, respectively. On multivariable Cox survival analysis, a higher NMHI was independently associated with improved long-term freedom from primary events (oHCM [Hazard ratio or HR 0.84 95 % Confidence Interval or CI 0.80–0.88] and nHCM [HR 0.95 95 % CI 0.91–9.97]), both p < 0.01. On penalized spline analysis, the NMHI at which the hazard for primary events crossed 1 was ∼$52,000 for both oHCM and nHCM. In nHCM patients, NMHI greater than $52,000 was associated with improved longer-term freedom from primary events vs. those whose NMHI was lower than $52,000 (196/1398 [14 %] vs. 203/1143 [18 %], log-rank p-value<0.01). Similarly, oHCM patients with NMHI greater than $52,000 had significantly improved longer-term freedom from primary events vs. those whose NMHI was lower than $52,000 (186/2067 [9 %] vs. 413/1760 [23 %] vs., log-rank p-value<0.001).

Conclusions

NMHI, a marker of socioeconomic status, is independently associated with outcomes in patients with HCM. oHCM patients below the NMHI cutoff had significantly worse long-term outcomes vs. the nHCM patients similarly below the NMHI cutoff.