MAPT and myotonic dystrophy type 1: The manifest DM1 group had significantly lower total tau compared with controls (DM1 vs. Controls estimate = −0.62, 95%CI −0.95: −0.28, P < 0.001), but the PreDM1 group did not differ from controls (Estimate = 0.09, 95% CI −0.44:0.62, P = 0.741).