Cross-Sectional Study of 24-Hour Urinary Electrolyte Excretion and Associated Health Outcomes in a Convenience Sample of Australian Primary Schoolchildren: The Salt and Other Nutrients in Children (SONIC) Study Protocol

Abstract

BackgroundDietary sodium and potassium are involved in the pathogenesis of cardiovascular disease. Data exploring the cardiovascular outcomes associated with these electrolytes within Australian children is sparse. Furthermore, an objective measure of sodium and potassium intake within this group is lacking.ObjectiveThe primary aim of the Salt and Other Nutrient Intakes in Children (“SONIC”) study was to measure sodium and potassium intakes in a sample of primary schoolchildren located in Victoria, Australia, using 24-hour urine collections. Secondary aims were to identify the dietary sources of sodium and potassium, examine the association between these electrolytes and cardiovascular risk factors, and assess children’s taste preferences and saltiness perception of manufactured foods.MethodsA cross-sectional study was conducted in a convenience sample of schoolchildren attending primary schools in Victoria, Australia. Participants completed one 24-hour urine collection, which was analyzed for sodium, potassium, and creatinine. Completeness of collections was assessed using collection time, total volume, and urinary creatinine. One 24-hour dietary recall was completed to assess dietary intake. Other data collected included blood pressure, body weight, height, waist and hip circumference. Children were also presented with high and low sodium variants of food products and asked to discriminate salt level and choose their preferred variant. Parents provided demographic information and information on use of discretionary salt. Descriptive statistics will be used to describe sodium and potassium intakes. Linear and logistic regression models with clustered robust standard errors will be used to assess the association between electrolyte intake and health outcomes (blood pressure and body mass index/BMI z-score and waist circumference) and to assess differences in taste preference and discrimination between high and low sodium foods, and correlations between preference, sodium intake, and covariates.ResultsA total of 780 children across 43 schools participated. The results from this study are expected at the end of 2015.ConclusionsThis study will provide the first objective measure of sodium and potassium intake in Australian schoolchildren and improve our understanding of the relationship of these electrolytes to cardiovascular risk factors. Furthermore, this study will provide insight into child taste preferences and explore related factors. Given the cardiovascular implications of consuming too much sodium and too little potassium, monitoring of these nutrients during childhood is an important public health initiative.

Association between Parent and Child Dietary Sodium and Potassium Intakes as Assessed by 24-h Urinary Excretion

“…In the current study participants were drawn from a convenience sample of children who were of a relatively high socioeconomic background [ 41 ], as such this limits the generalizability of the findings across broader soceioeconomic groups. Furthermore, the study was limited by a low response rate [ 14 ] and parental self-selection for inclusion. It is also possible that participants had an interest in health and hence may be different from the general population.…”

“…A cross-sectional study, Salt and Other Nutrient Intakes in Children (SONIC) was conducted in Victoria, Australia from June 2010 to May 2013. Full details of the SONIC study design, procedures and protocols have been published elsewhere [ 14 ]. This analysis included children (including sibling pairs and trios) ( n = 191) who had a parent ( n = 171) complete a 24-h urine collection.…”

“…Information on age and gender were obtained using a questionnaire completed by parents. Height and weight of the children was measured on site by trained researchers using standard protocols [ 14 ]. Body mass index (BMI) was calculated as body weight (kg) divided by the square of body height (m 2 ).…”

“…Participants could opt to complete the 24-h urine collection on a school day or non-school day. All were instructed to commence the collection at any suitable time and followed the usual 24-h urine protocol by emptying their bladder, discarding this urine, and recording this as the start time [ 14 ]. Following this all urine was collected until the corresponding 24-h finish time.…”

Urinary sodium is positively associated with urinary free cortisol and total cortisol metabolites in a cross-sectional sample of Australian schoolchildren aged 5–12 years and their mothers

“…24 h urine collection. The 24 h urine collection protocol has been described elsewhere (4,21) . In brief, at the start of the 24 h urine collection, children and mothers were instructed to empty their bladder, discard this urine and note this as the start time of their collection.…”