Greater plasma GDF15 was associated with lower total brain (βi = −9.257 [1.51, p < 0.001]), gray matter (βi = −5.454 [1.03, p < 0.001]), white matter (βi = −6.230 [1.01, p < 0.001]), and higher ventricle CSF volumes (βi = 4.06 [0.77, p < 0.001]), SPARE‐AD (βi = 0.173 [0.04, p < 0.001]), and SPARE‐BA (βi = 1.16 [0.31, p < 0.001]) at age 75. The gene discussed is GDF15; the disease is Alzheimer disease.