Long term effect of cART treatment on free water and neurofilament light chain. The box-and-whisker plots illustrate the comparison of free water (FW) index between the HIV+ and HIV- participants, and the temporal trends of FW from baseline and follow-up visits in (A) gray matter (GM), (B) white matter (WM); (C) average NfL concentration. There is no significant between-cohort difference of long-term temporal progression in FW (in GM and WM), and NfL. Note, BSL, baseline; W12, week-12 (new BSL for HIV+); Y1, year-1; Y2, year-2; NfL data were not collected at Y1 for HIV− participants. + sign indicates the mean FW at each time point and cohort. Significant differences are also shown.