Background:
This study assesses racial/ethnic differences in CVD outcomes among patients with hypertension (HTN) or type 2 diabetes (T2DM) across Asian American subgroups (Asian Indian, Chinese, Filipino, Japanese, Korean, Vietnamese), Mexican, non-Hispanic black (NHB), and non-Hispanic White (NHW) in a large, mixed payer ambulatory care setting in northern California.
Study Design: We estimated the rate of CVD incidence among adult patients with HTN (N=171,864) or T2DM (N=10,570), or both (N=36,589) using electronic health records between 2000-2013. Average follow-up was 4.5 years. CVD, including CHD (410-414), PVD (415, 440.2, 440.3, 443.9, 451, 453), and stroke (430-434), was defined by ICD-9 codes; HTN and T2DM were defined by ICD-9 codes, medication history, or two or more elevated blood pressure measures/abnormal glucose lab test results. Cox proportional hazard models were used to estimate hazard ratios for CHD, PVD, and stroke across race/ethnicity.
Results:
Among these patients, 10.5% developed CVD by the end of year 2013 (5.4% CHD, 3.4%PVD, 3.6% stroke).
There was a gender difference in the risk of incident CHD. Among males, the age-adjusted hazard ratios for CHD were significantly higher for Asian Indians (HR: 1.3, 95% CI: 1.2-1.5) and significantly lower for Chinese (HR: 0.6, CI: 0.5-0.7) and Japanese (HR: 0.8, CI: 0.6-0.9) compared to NHWs. Among females, the age-adjusted hazard ratios for CHD were significantly higher for Mexican (HR: 1.3, CI: 1.1-1.5) and NHBs (HR: 1.7, CI: 1.4-2.0) and significantly lower for Chinese (HR: 0.6, CI: 0.5-0.7) and Japanese (HR: 0.5, CI: 0.4-0.7). NHB men and women also had significantly higher age-adjusted hazard ratios for PVD (men: HR: 1.5, CI: 1.2-1.9; women: HR: 1.6, CI: 1.3-1.9) and stroke (men: HR: 1.3, CI: 1.1-1.7; women: HR: 1.3, CI: 1.1-1.6) compared to NHWs. The age-adjusted hazard ratios for PVD and stroke were lower or equivalent to NHWs for all Asian subgroups and Mexican men and women. Patients with both HTN and T2DM were at elevated risk to develop CVD compared to patients with only one of the two conditions, regardless of their race/ethnicity.
Conclusions:
Compared to previous studies, we found less racial/ethnic variation in CVD outcomes, in particular stroke, among patients with HTN or T2DM. Our finding suggests the higher stroke incidence rates in several races/ethnicities are likely to be explained by the higher prevalence of HTN and T2DM among these groups. However, Asian Indian men and NHB and Mexican women with HTN or T2DM were at elevated risk for CHD compared to NHWs. Since the majority of patients in the study cohort had health insurance, further studies are needed to better understand the reasons for the observed racial/ethnic differences beyond disparities in access to health care. Special attention needs to be paid to patients with multiple conditions.
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