Estimating mean change in population salt intake using spot urine samples.

Area of Science:

• Public Health
• Nutritional Epidemiology
• Biomarkers

Background:

• Estimating population daily salt intake typically relies on 24-hour urine samples, which are burdensome for participants.
• Spot urine samples offer a less invasive alternative, but their utility in tracking changes in population salt intake over time remains unclear.
• This study investigates whether established equations using spot urine data can accurately reflect population-level shifts in salt consumption compared to traditional 24-hour collections.

Purpose of the Study:

• To compare the accuracy of estimating equations based on spot urine samples versus 24-hour urine collections for detecting changes in mean population daily salt intake.
• To assess the feasibility of using simpler spot urine methods for longitudinal public health surveillance of salt intake.

Main Methods:

• Paired and unpaired 24-hour and spot urine samples were collected from Australian adults in 2011 and 2014.
• Estimates of change in mean daily salt intake were derived from 24-hour samples and by applying various established equations (Kawasaki, Tanaka, Mage, Toft, INTERSALT) to spot urine data.
• Statistical analyses, including mixed models, were used to compare the changes detected by both methods.

Main Results:

• A significant decrease in mean daily salt intake was detected by 24-hour urine samples (-0.48g/day).
• Estimating equations applied to spot urine samples also identified significant decreases, with values ranging from -0.20g/day to -0.51g/day across different equations.
• No statistically significant differences were found between the changes estimated by 24-hour samples and the spot urine-based equations, particularly when analyzing paired data.

Conclusions:

• Spot urine-based estimating equations demonstrated a similar ability to detect changes in population salt intake over time as 24-hour urine collections.
• These findings suggest that spot urine samples may offer a practical and effective approach for monitoring population salt intake trends.
• Further research in larger, diverse populations is recommended to validate these methods for widespread public health application.