Daily salt intake is an independent risk factor for pollakiuria and nocturia.

OBJECTIVE

To clarify the relationships between daily salt intake and lower urinary tract symptoms.

METHODS

A cross-sectional clinical study was carried out with 728 patients. Spot urine samples were collected to evaluate estimated daily salt intake. The patients were divided into two groups based on mean salt intake (9.2 g/day). Their urinary condition was evaluated using the Core Lower Urinary Tract Symptoms score and 3-day frequency volume charts. The influence of salt intake on lower urinary tract symptoms was investigated using multivariate logistic regression analysis.

RESULTS

Daytime frequency (Q1) and nocturia (Q2) in the high salt intake group (H-salt group) were higher compared with those in the low salt intake group (L-salt group); P < 0.001). The quality of life scores and nocturnal polyuria index in the H-salt group were worse than those in the L-salt group (P < 0.001). Multivariate analyses showed daily salt intake is an independent worsening factor for high daytime frequency (odds ratio 2.32, 95% confidential interval 1.66-3.25, P < 0.001) and nocturia (odds ratio 3.05, 95% confidential interval 2.08-4.52, P < 0.001). Similarly, hypertension was identified as the independent variable for these symptoms. A limitation of the present study was that we recruited only patients with mild or no comorbidity.

CONCLUSIONS

Excessive daily salt intake negatively affects pollakiuria and nocturia. The presence of hypertension can also represent a worsening factor for these symptoms. Although not shown by prospective study, the appropriate control of salt intake and blood pressure might be important for the treatment of pollakiuria and nocturia.