Factors Associated with Non-Adherence to Antiretroviral Treatment in People Living with HIV Treated at a Mexican Tertiary Hospital: A Cross-Sectional Study

Antiretroviral therapy (ART) adherence remains a major challenge in HIV care despite the widespread use of integrase strand transfer inhibitor (INSTI)-based regimens. This study aimed to identify factors associated with ART non-adherence among people living with HIV at a tertiary referral hospital in Mexico. In this cross-sectional study (February–May 2023), adherence was assessed with the Simplified Medication Adherence Questionnaire (SMAQ), and virological suppression was defined as a viral load < 50 copies/mL. Associated factors were evaluated with multivariable logistic regression. Among 296 participants, 104 (35.1%) were non-adherent, and 279 (94.3%) had an undetectable viral load, including 95 of the 104 non-adherent participants (91.3%). Tobacco use was associated with higher odds of non-adherence (adjusted odds ratio [AOR] = 1.80; 95% CI: 1.03–3.14), and older age with lower odds (AOR = 0.73 per 10-year increase; 95% CI: 0.56–0.95). Sustained non-adherence was more frequent among viremic than suppressed participants (41.2% vs. 10.0%; p = 0.001), whereas occasional missed doses were common among those with suppression. Non-adherence remains common despite high virological suppression in the INSTI era. Younger people and those who smoke may benefit most from adherence support, and distinguishing occasional from sustained non-adherence may help interpret self-reported adherence.