COLORADO SPRINGS — The intake ratio of sodium to potassium bears a much stronger association with subsequent development of cardiovascular disease than does consumption of either alone, according to new findings from the Trials of Hypertension Followup (TOPH) Study.
“We found that sodium and potassium may have a joint effect on the development of cardiovascular disease, in keeping with a proposed biologic symmetry. In our data the ratio was the most important predictor,” Nancy R. Cook, Sc.D., reported at a conference of the American Heart Association.
She presented a 10- to 15-year follow-up of 2,275 participants in TOPH-I and -II, a pair of National Institutes of Health-sponsored randomized clinical trials of sodium reduction and other interventions aimed at preventing hypertension in individuals who were prehypertensive at baseline. There were 193 cardiovascular events—acute MI, stroke, revascularization procedures, or cardiovascular death—during follow-up.
A key feature of both studies was the periodic collection of 24-hour urine sodium and potassium excretions over several years.
In the TOPH follow-up analysis, there was a significant, linear relationship with cardiovascular risk from lowest to highest quartile of the sodium to potassium excretion ratio.
After full statistical adjustment for numerous variables, including demographics, alcohol intake, body weight, physical activity, smoking status, and changes in those variables over the course of the study, individuals in the highest quartile of sodium to potassium ratio had a highly significant 50% increased risk of a cardiovascular event during follow-up, compared with those in the lowest quartile. For each unit increase in sodium to potassium ratio, future cardiovascular risk rose by 24%, added Dr. Cook of Brigham and Women's Hospital, Boston, and the Harvard School of Public Health.
The mean ratio was 2.9 in both men and women in the study population as a whole. But it differed modestly by age and more profoundly by race. Black participants had lower potassium excretion levels than whites, leading to a much higher sodium to potassium ratio of 3.4. Considered separately, neither sodium nor potassium excretion alone was significantly related to cardiovascular risk across quartiles.