Assessing Differences in Mortality Rates and Risk Factors Between Hispanic and Non-Hispanic Patients With Cystic Fibrosis in California

Abstract

Background: Over the past 30 years, therapeutic advances have extended the median lifespan of patients with cystic fibrosis (CF). Hispanic patients are a vulnerable subpopulation with a high prevalence of risk factors for worse health outcomes. The consequences of these differences on health outcomes have not been well described. The objective of this study was to characterize the difference in health outcomes, including mortality rate, between Hispanic and non-Hispanic patients with CF.

Methods: This study is a retrospective analysis of CF Foundation Patient Registry data of California residents with CF, diagnosed during or after 1991, from 1991 to 2010. Ethnicity was self-reported. The primary outcome was mortality. Hazard ratios were estimated from a Cox regression model, stratified by sex, and adjusted for socioeconomic status, clinical risk factors, and year of diagnosis.

Results: Of 1,719 patients, 485 (28.2%) self-identified as Hispanic. Eighty-five deaths occurred, with an overall mortality rate of 4.9%. The unadjusted mortality rate was higher among Hispanic patients than among non-Hispanic patients (9.1% vs 3.3%, P < .0001). Compared with non-Hispanic patients, Hispanic patients had a lower survival rate 18 years after diagnosis (75.9% vs 91.5%, P < .0001). Adjusted for socioeconomic status and clinical risk factors, Hispanic patients had an increased rate of death compared with non-Hispanic patients (hazard ratio, 2.81; 95% CI, 1.70-4.63).

Conclusions: Hispanic patients with CF have a higher mortality rate than do non-Hispanic patients, even after adjusting for socioeconomic status and clinical severity. Further investigation into the mechanism for the measured difference in lung function will help inform interventions and improve the health of all patients with CF.

Keywords: cystic fibrosis; ethnicity; health disparities; pediatric pulmonology.

Figure 1

Flowchart of study cohort. Of the 4,387 California residents in the CF Foundation Patient Registry, 1,724 received the diagnosis during or after 1991 and before 18 years of age. All had recorded ethnicity. Five patients were excluded because of missing insurance data. The final cohort for analysis was 1,719 patients. Hispanic patients made up 28.2% of the total patient population available for analysis. The unadjusted mortality rate was higher in Hispanic patients. CF = cystic fibrosis.

Figure 2

Kaplan-Meier plot shows a difference in survival rates between Hispanic and non-Hispanic patients with CF. Hispanic patients (red): n = 485 (44 failed, 441 censored). Non-Hispanic patients (blue): n = 1,234 (41 failed, 1,193 censored). Log-rank χ², 35.0647; df = 1; P < .0001. CF Foundation Patient Registry, California, 1991-2010. See Figure 1 legend for expansion of abbreviation.

Figure 3

A, B, Plots of mean FEV₁ % pred by age and median BMI z score by age from all clinical encounters stratified by ethnicity. A, At 6 years of age, the mean FEV₁ for Hispanic patients (red) is lower than for non-Hispanic patients (blue), (77% pred [SD, 23% pred] and 89% pred [SD, 20% pred], respectively, P < .0001). The yearly rate of decline in mean FEV₁ % pred is not different between the two groups. FEV₁ was best predicted by a random-effects model without interaction of age and ethnicity. (Difference in corrected Akaike’s information criteria (AICc), 1.85; information ratio, 2.53; F test 0.7026) B, The yearly rate of decline in median BMI z score is not different between the two groups. BMI was best predicted by a random-effects model without interaction of age and ethnicity. (Difference in AICc, 3.5; information ratio, 5.76. Sum of squares was lower for less complicated model.) CF Foundation Patient Registry, California, 1991-2010. % pred = % predicted value. See Figure 1 legend for expansion of other abbreviation.