Association between the calendar year of combination antiretroviral therapy initiation and time to attrition stratified by observation time.

Note: HR = hazard ratio; 95% CI = 95% Confidence Interval; † Includes the year of starting cART and patients’ age, gender, marriage status, HIV exposure category, CD4 cell counts at enrollment, hemoglobin level, counts of baseline symptoms, area of residence, health care setting and initial regimens but excludes initial regimens. ‡ Includes all factors plus initial regimens.