Background: Previous cross sectional studies have been inconsistent in demonstrating a relationship between 24h urinary sodium (24hUNa), 24h urinary potassium (24hUK)  and 24h urinary sodium-to-potassium (24hUNa/K) ratio with systolic blood pressure. There are no such  previous studies in patients with diabetes and none assessing the relationship between 24hUNa/K ratio and renin angiotensin aldosterone system activity. In this study, we examined the relationship between 24hUNa/K ratio with blood pressure and RAAS activity in patients with diabetes mellitus.

 Methods: In a cross-sectional study, clinical characteristics, 24hUNa, and 24h urinary potasium (24hUK) were recorded in 328 consecutive patients with diabetes attending diabetes clinics at a tertiary referral hospital in Melbourne. Plasma renin activity (PRA) and serum aldosterone were measured in 222 patients.

Results: The mean age was 64±15 years, 60% were males and 77% had type 2 diabetes. The  mean 24hUNa, mean 24hUK and mean 24hNa/K ratio was 164±72 mmol/24h, 71±26 mmol/24h and 2.5±1.2,  respectively. These levels compared to 155±63 mmol/24h for 24hUNa, 82±28 mmol/24h for 24hUK, and 2±0.8 for 24hUNa/K ratio in a group of similar aged community participants from previous study¹ . There was no relationship between 24hUNa, 24hUK and 24hUNa/K ratio with systolic, diastolic or mean arterial blood pressure in the entire cohort. There was no relationship between 24hU/K ratio with PRA.  However, serum aldosterone level negatively correlated with 24hUNa/K ratio (r= -0.22, p=0.001).

Conclusions: Although the 24hUNa/K ratio in patients with diabetes was higher than in the general population,  there was no relationship between Na/K ratio and blood pressure in this group of patients. Higher 24hUNa/K ratio was associated with lower serum aldosterone levels in people with diabetes.