Fasting serum potassium and long-term mortality in healthy men.

Background: Serum potassium levels have been positively associated with cardiovascular mortality, but little is known about the association with cancer mortality and death due to other causes. We examined whether serum levels of potassium were associated with long-term mortality in a healthy cohort.

Methods: Oslo Ischemia Study invited 2341 initially healthy men aged 40-59 years with no use of medication to a comprehensive health survey in 1972. Fasting serum level of potassium (mmol/L) was ascertained at baseline for 1989 men. We have complete follow-up for death throughout 2017. Cox proportional hazard models were used to calculate hazard ratios (HRs) with 95% confidence intervals (CIs) and adjusted for multiple confounders.

Results: After a median follow-up of 30 years (interquartile range 21.2-38.7), 1736 deaths were observed, of which 494 were cancer deaths, 688 cardiovascular deaths, and 536 deaths related to other causes. Restricted cubic spline analysis showed that potassium level was linearly and positively associated with long-term cancer mortality; HR per mmol/L 1.8, 95% CI 1.4-2.4. Compared with low levels of potassium (≤ 4.0 mmol/L), men with high levels (≥4.6 mmol/L) showed a significantly 78% higher risk of cancer death. A positive linear association was found for all-cause mortality (HR per mmol/L 1.6, 95% CI 1.4-1.8), and for cardiovascular (HR per mmol/L 1.4, 95% CI 1.1-1.7) and other cause mortality (HR per mmol/L 1.7, 95% CI 1.3-2.2).

Conclusions: These findings suggest that serum potassium level appears to predict long-term mortality in healthy middle-aged men, and it might imply future surveillance strategies for individuals with high serum potassium levels.