In general, our results provide evidence on the role of BBB in the etiology of dementia-causing diseases by suggesting that higher plasma levels of the tight junction component TJP1 (ref. 39) and proteins degrading the tight junction, such as AIMP1 (ref. 40) and BIN1 (ref. 41), increase—and higher levels of barrier-protecting IL-17F42 reduce—the risk of Alzheimer’s disease. The gene discussed is TJP1; the disease is Alzheimer disease.