Assessing comorbidities and survival in HIV-infected and uninfected matched Medicare enrollees.

OBJECTIVE People with HIV infection experience excessive mortality compared with their noninfected counterparts. It is unclear whether the impact of HIV infection on mortality varies by comorbidities or whether sex difference exists in this relationship. This study assessed the effect of newly diagnosed HIV infection on overall mortality among Medicare beneficiaries for both disabled and older adults (≥65 years old) based on their original entitlement. METHODS We constructed a retrospective matched cohort using a 5% nationally representative sample of Medicare beneficiaries between 1996 and 2015. People with incident HIV diagnoses were individually matched to up to three controls based on demographics. Cox proportional hazards models adjusted for baseline demographics and comorbidities were used to assess the effect of HIV status on survival among four disabled groups by sex strata. Within each stratum, interactions between comorbidity variables and HIV status were examined. RESULTS People with HIV, especially older women, had a higher prevalence of baseline comorbidities than controls. HIV--mortality association varied according to sex in older adults (P = 0.004). Comorbidity--HIV interactions were more pronounced in disabled groups (P < 0.0001). People with HIV with more chronic conditions had a less pronounced increase in the risk of death than those with fewer conditions, compared with uninfected controls. CONCLUSION Medicare enrollees with newly diagnosed HIV had more prevalent baseline comorbidities and were at higher risk of death than people without HIV. HIV infection has a more pronounced effect among those with fewer comorbidities. Sex differences in HIV--mortality association exist among older Medicare enrollees.