Weight Trajectories Across Antiretroviral Therapy Regimen Switches in Older People With HIV in China: A Nationwide Multicenter Cohort Study

BACKGROUND: As China's HIV epidemic ages rapidly, evaluating metabolic risks in older people with HIV (PWH) is increasingly urgent. Weight gain associated with integrase strand transfer inhibitors (INSTIs) has drawn increasing attention, but data on older Chinese PWH remain scarce. METHODS: We conducted a retrospective cohort study of PWH aged ≥ 50 years across 19 cities in China within the National Free Antiretroviral Therapy Programme. We assessed weight change trajectories across antiretroviral therapy regimen switches among non-nucleoside reverse transcriptase inhibitors (NNRTIs), INSTIs, and protease inhibitors (PIs), using piecewise mixed-effects models and restricted cubic splines. We performed subgroup analyses to assess whether associations differed by sex, age, and baseline metabolic risk. RESULTS: Among 5618 participants, the adjusted weight-change slope increased from 0.41 kg/year before switching to 0.90 kg/year afterward (p = 0.03). Slope changes were +0.76 kg/year for NNRTI→INSTI (p = 0.03), +4.76 kg/year for PI→INSTI (p < 0.01), and -2.07 kg/year for INSTI→NNRTI (p = 0.03). Exploratory analyses suggested numerically stronger associations among females, adults aged ≥ 65 years, and participants with baseline metabolic risk. CONCLUSIONS: Switching to INSTI-based regimens was associated with steeper weight-gain trajectories compared to switching to other regimens, while switching from an INSTI to an NNRTI was associated with attenuation. These findings support weight and cardiometabolic monitoring after regimen changes, while decisions regarding ART modification should remain individualized.