The following peripheral blood levels will be measured over a 24-hour period, at multiple time points, in all participants: TNF-alphaRI and IL-6 (sleep-regulating cytokines); IFN-gamma and IL-12 (cytotoxic or TH1 cytokines); and IL-10 and IL-1RA (inflammatory or TH2 cytokines). This will help to determine the association between alterations in sleep-regulating cytokines and HIV disease progression (CD4+ T-cell count, HIV-1 RNA level).