In one study from Brazil that included 83 patients recruited from rehabilitation hospitals (mean age 55.3 years), all of whom had HAM/TSP, and 88 healthy controls, HTLV-1 infection was associated with decreased global cognition and with decreased executive function, an association the authors thought was possibly related to interleukin 6 [10]. The gene discussed is IL6; the disease is tropical spastic paraparesis.