The association of schooling, sibling life situation, and dietary habits with the estimated 24-h urinary salt excretion and sodium-to-potassium ratio in 3-year-old children.

Objectives: We examined the association of schooling, sibling life situation, and dietary habits with the estimated 24-h urinary salt excretion and the urinary sodium-to-potassium (Na/K) ratio in 3-year-old children.

Methods: The subjects were 639 children who underwent a health checkup in four cities and towns in Kyoto Prefecture from January to November 2019. The children's parents answered questionnaires about weekday childcare places, the birth order, and the awareness of reducing the salt intake. The questions on food intake frequency included 10 items. The estimated 24-h salt excretion and Na/K ratio were calculated from the participants' first voiding urine in the morning.

Results: Data were available for 294 children. The median (interquartile range (IQR)) of salt excretion (g/day) was 2.6 (1.7-3.4), and urinary Na/K ratio (mmol ratio) was 2.6 (1.6-4.1). Multinomial logistic regression analysis showed that the group with older siblings was significantly associated with high salt (odds ratio 1.89 (95% confidence interval 1.04 to 3.46)). In the urinary Na/K ratio, the nursery group had a significantly lower Na/K (odds ratio 0.32 (0.17 to 0.60)). High processed meat products intake was associated with a higher Na/K (odds ratio 1.96 (1.05-3.66)), whereas high vegetable intake was associated with a lower Na/K (odds ratio 0.45 (0.23-0.87)). Other factors showed no significant associations.

Conclusions: In Japanese 3-year-old children, the estimated 24-h urinary salt excretion was associated with older siblings, and the urinary Na/K ratios were associated with schooling situation and the intake of processed meat products and vegetables.