SHBG and Alzheimer disease: This is in line with findings by Hogervorst, Bandelow, Combrinck, & Smith (2004), which showed that SHBG levels were associated with risk of Alzheimer's disease in younger older men (mean age = 66) but that total testosterone levels were associated with the disease in the older participants (mean age = 80) (Hogervorst et al., 2004).