Cohort Profile: Recruitment cohorts in the neuropsychological substudy of the Multicenter AIDS Cohort Study.

The Multicenter AIDS Cohort Study (MACS) is one of the largest and longest running studies of the natural and treated history of HIV disease. The Neuropsychological (NP) substudy was begun in 1988 following reports of significant adverse neurological consequences of HIV disease, including dementia. The goal was to characterize the neuropsychological deficits among individuals with HIV disease, and track the natural history of the neurological complications over time. There were three distinct MACS recruitment stages that focused on different groups of HIV-infected men, or men at risk for infection. Initially, a subcohort was evaluated semi-annually with NP tests but, beginning in 2005, the entire group of MACS participants have had NP examinations biannually, unless closer follow-up was warranted. The participants complete a battery of NP tests, and are classified as either normal, mildly or severely impaired using the Antinori criteria for HIV-Associated Neurocognitive Disorder (HAND). Additional behavioural data, including mood state and psychoactive substance use, are recorded as part of the main MACS data collection. The MACS public data set (PDS) has been available since 1994 and includes baseline and 6-monthly follow-up data. Beginning in October 1995, the PDS has been released annually with new releases superseding previous versions.