SLC6A3 and Alzheimer disease: Cigarette smoking may have indirect effects on the mesolimbic dopaminergic system.[36] Yang et al[37] and Newberg et al[38] reported a decrease in striatal DAT availability in smokers compared with nonsmokers; however, this association was not found in another study.[39] The present study found no correlation between the number of cigarettes smoked per day and striatal DAT availability (rho = −0.269, P = 0.062, data not shown) in the total patients with AD.