Association between sodium and potassium excretion estimated from spot urine and socioeconomic status among primary school children and their mothers in Okinawa, Japan

Hypertension is the greatest and the most preventable risk factor for cardiovascular disease. Excessive sodium (Na) intake and insufficient potassium (K) intake have been identified as risk factors for hypertension. Socioeconomic status (SES) may be related to diet quality. In Japan, few studies have examined the relationship between urinary Na and K excretion and SES in adults, and there are no studies in children. In 2014, 1944 children (1382 households) in all public elementary schools in Yaese town, Okinawa, Japan were recruited to participate in a study. Casual urine specimens were collected to estimate 24-h urinary Na and K excretion and urinary Na/K ratio. Mother's educational background and household incomes were assessed and used as indicators of SES. A total of 236 pairs of children and their mothers were analyzed in this study. Urinary Na and K excretion were not significantly related to educational levels of mothers and household incomes in children. On the other hand, in mothers, lower household income group had higher 24-h estimated urinary Na excretion and urinary Na/K ratio than other groups. There was no significant difference between urinary excretion and educational levels in mothers. Household income disparities in urinary levels seen in mothers were not seen in children. There may be some factors that moderate the dietary inequalities in children.