In the CSF biomarker subset, after adjustment for tau and log2WMH, lower baseline CSF Aβ42 was associated with increased whole‐brain atrophy rates in controls with a 10 pg/ml decrease in concentration of Aβ42 associated with an increase in whole‐brain atrophy rate of 0.2 ml/year (0.06–0.3). This evidence concerns the gene MAPT and Brain atrophy.