Estimating mean change in population salt intake using spot urine samples

Petersen, Kristina S., Wu, Jason H. Y., Webster, Jacqui, Grimes, Carley, Woodward, Mark, Nowson, Caryl A. and Neal, Bruce 2017, Estimating mean change in population salt intake using spot urine samples, International journal of epidemiology, vol. 46, no. 5, pp. 1542-1550, doi: 10.1093/ije/dyw239.

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Title Estimating mean change in population salt intake using spot urine samples
Author(s) Petersen, Kristina S.
Wu, Jason H. Y.
Webster, Jacqui
Grimes, CarleyORCID iD for Grimes, Carley
Woodward, Mark
Nowson, Caryl A.ORCID iD for Nowson, Caryl A.
Neal, Bruce
Journal name International journal of epidemiology
Volume number 46
Issue number 5
Start page 1542
End page 1550
Total pages 9
Publisher Oxford University Press
Place of publication Oxford, Eng.
Publication date 2017-10
ISSN 0300-5771
Keyword(s) salt intake
spot urine collection
24-h urine collection
Summary Background: Spot urine samples are easier to collect than 24-h urine samples and have been used with estimating equations to derive the mean daily salt intake of a population. Whether equations using data from spot urine samples can also be used to estimate change in mean daily population salt intake over time is unknown. We compared estimates of change in mean daily population salt intake based upon 24-h urine collections with estimates derived using equations based on spot urine samples.

Methods: Paired and unpaired 24-h urine samples and spot urine samples were collected from individuals in two Australian populations, in 2011 and 2014. Estimates of change in daily mean population salt intake between 2011 and 2014 were obtained directly from the 24-h urine samples and by applying established estimating equations (Kawasaki, Tanaka, Mage, Toft, INTERSALT) to the data from spot urine samples. Differences between 2011 and 2014 were calculated using mixed models.

Results: A total of 1000 participants provided a 24-h urine sample and a spot urine sample in 2011, and 1012 did so in 2014 (paired samples n = 870; unpaired samples n = 1142). The participants were community-dwelling individuals living in the State of Victoria or the town of Lithgow in the State of New South Wales, Australia, with a mean age of 55 years in 2011. The mean (95% confidence interval) difference in population salt intake between 2011 and 2014 determined from the 24-h urine samples was -0.48g/day (-0.74 to -0.21; P < 0.001). The corresponding result estimated from the spot urine samples was -0.24 g/day (-0.42 to -0.06; P = 0.01) using the Tanaka equation, -0.42 g/day (-0.70 to -0.13; p = 0.004) using the Kawasaki equation, -0.51 g/day (-1.00 to -0.01; P = 0.046) using the Mage equation, -0.26 g/day (-0.42 to -0.10; P = 0.001) using the Toft equation, -0.20 g/day (-0.32 to -0.09; P = 0.001) using the INTERSALT equation and -0.27 g/day (-0.39 to -0.15; P < 0.001) using the INTERSALT equation with potassium. There was no evidence that the changes detected by the 24-h collections and estimating equations were different (all P > 0.058). Separate analysis of the unpaired and paired data showed that detection of change by the estimating equations was observed only in the paired data.

Conclusions: All the estimating equations based upon spot urine samples identified a similar change in daily salt intake to that detected by the 24-h urine samples. Methods based upon spot urine samples may provide an approach to measuring change in mean population salt intake, although further investigation in larger and more diverse population groups is required.
Language eng
DOI 10.1093/ije/dyw239
Field of Research 111799 Public Health and Health Services not elsewhere classified
0104 Statistics
1117 Public Health And Health Services
Socio Economic Objective 970111 Expanding Knowledge in the Medical and Health Sciences
HERDC Research category C1 Refereed article in a scholarly journal
ERA Research output type C Journal article
Copyright notice ©2016, The Authors
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