Low serum potassium in mid life associated with decreased cerebrospinal fluid Aβ42 in late life

Low serum potassium increases risk of hypertension and stroke, and cardiovascular factors increase the risk of Alzheimer disease (AD). We examined the association between serum potassium and the biologic marker cerebrospinal fluid amyloid-beta (Aβ42), which is decreased in Alzheimer disease patients. Psychiatric examinations, laboratory and other tests were conducted on a population-based sample of 1080 women aged 46 to 60 in 1968, with follow-ups in 1974, 1980, and 1992. In 1992, cerebrospinal fluid Aβ42 levels were obtained from 81 women. Increasing serum potassium in 1968 was associated with increasing cerebrospinal fluid Aβ42 (beta = 153.9, P = 0.041) in 1992 using age-adjusted linear regression. Compared with the lowest tertile of potassium, the middle (beta = 95.3, P = 0.138) and highest tertiles (beta = 193.5, P = 0.004) had incrementally increased cerebrospinal fluid Aβ42 levels. Associations remained after controlling for blood pressure and other factors, and were similar among the 17 women in 1974 with available serum potassium. Potassium in 1980 and 1992 was not associated with cerebrospinal fluid Aβ42. Findings suggest low serum potassium in mid life, but not late life, is associated with low cerebrospinal fluid Aβ42 levels in late life. It is possible potassium co-varies with another variable that is associated with cerebrospinal fluid Aβ42. Nonetheless, serum potassium is a modifiable risk factor and further examination of the potassium-dementia relationship is warranted.