Table 1

Twenty-four-hour urinary electrolyte excretion by age group and sex among participants aged 4–12 years*

Urinary marker4–12 years4–8 years9–12 years
No of participants666365301283159124383206177
Sodium (mmol/day)103±2109±3‡97±390±2§94±2‡85±3113±3120±4‡105±3
Salt equivalent (g/day)6.1±0.16.4±0.2‡5.7±0.25.3±0.1§5.5±0.1‡5.0±0.26.6±0.27.0±0.2‡6.1±0.2
Potassium (mmol/day)47±149±1‡44±141±1§42±1‡39±151±154±2‡47±2
Na:K (molar ratio)2.4±0.052.4±0.062.3±0.062.4±0.62.4±0.82.3±0.092.4±0.62.4±0.92.4±0.6
Creatinine (mmol/day)5.6±0.15.8±0.25.3±0.24.3±0.14.5±0.14.1±0.16.5±0.16.8±0.26.1±0.2
Volume output (mL/day)866±22889±29838±26748±20748±21748±35953±26997±40902±34
  • *Linear regression with adjustment for school cluster was used to assess differences in the excretion of sodium, salt equivalent, potassium and Na:K molar ratio between subgroups.

  • †Additional adjustment for age, day of urine collection and BMI z-score did not alter results in any of the age or sex-subgroup analyses (data not shown). This was with the exception of urinary potassium excretion, which was no longer significantly higher in boys (fully adjusted model p=0.06) within the age stratified sub-group analyses of 9–12 years.

  • ‡<0.05, significant difference between boys and girls.

  • §<0.05, significant difference between age groups, that is, 4–8 years versus 9–12 years.