Long-term compliance with salt restriction assessed using the spot urine method in Japanese cardiology outpatients

The purpose of this study was to evaluate long-term compliance with salt restriction in Japanese cardiology outpatients assessed by spot urine measurements. A total of 466 patients (72±10 years old, 216 females) who visited a cardiology outpatient clinic and were followed for at least 1 year were included in this study. Daily dietary salt intake was estimated based on the sodium and creatinine concentrations determined by spot urine at the time of enrollment, during an 8-26 week follow-up and at a long-term follow-up (>1 year). The average follow-up duration was 2.2±0.6 (1.0-3.4) years after enrollment, and spot urines were collected 5.2±2.8 times after 1 year. The baseline estimated salt excretion was 9.6±2.7 g per day, which was reduced to 8.7±2.3 g per day (P<0.01) at 8-26 weeks and remained unchanged at the long-term follow-up (8.9±2.0 g per day, P=0.36 vs. 8-26 weeks, P<0.01 vs. baseline). The percent of patients who achieved an average salt excretion<6.0 g per day was unchanged from baseline (6.9% vs. 7.7%, P=0.61). Among several variables (gender, age, body weight, salt excretion at enrollment) that might affect the incidence of salt excretion <6.0 g per day, salt excretion at baseline was the only determinant of successful salt restriction (P<0.01). In conclusion, compliance with salt restriction, assessed using a spot urine method, was maintained over the long term; however, achieving salt reduction to the level recommended by the guidelines remains a challenge.