Longer exposures of 2-month-old rats or 3-month-old APP/PS1 transgenic mice to sidestream cigarette smoke (1h/day x 5 days/wk x two or 4 months) induces tau and amyloid pathology like that reported in MCI and patients with dementia (Ho et al., 2012; Moreno-Gonzalez et al., 2013). This evidence concerns the gene MAPT and dementia.