Salt intake assessed by 24 h urinary sodium excretion in a random and opportunistic sample in Australia.
OBJECTIVE
The gold standard method for measuring population sodium intake is based on a 24 h urine collection carried out in a random population sample. However, because participant burden is high, response rates are typically low with less than one in four agreeing to provide specimens. At this low level of response it is possible that simply asking for volunteers would produce the same results.


METHODS
Lithgow, New South Wales, Australia.


METHODS
We randomly selected 2152 adults and obtained usable 24 h urine samples from 306 (response rate 16%). Specimens were also collected from a further 113 volunteers. Estimated salt consumption and the costs for each strategy were compared.


RESULTS
The characteristics of the 'random' and 'volunteer' samples were moderately different in mean age 58 (SD 14.6 vs 49(17.7) years, respectively; p<0.001) as well as self-reported alcohol use, tobacco use, history of hypertension and prescription drug use (all p<0.04). Overall crude mean 24 h urinary salt excretion was 8.9(3.6) g/day in the random sample vs 8.5(3.3) g/day for the volunteers (p=0.42). Corresponding age-adjusted and sex-adjusted estimates were 9.2(3.3) and 8.8(3.4) g/day (p=0.29). Estimates for men 10.3(3.8) vs 9.6(3.3) g/day; (p=0.26) and women 7.6(3) vs 7.9(3.2) g/day; (p=0.43) were also similar for the two samples, as was salt excretion across age groups (p=0.72). The cost of obtaining each 24 h urine sample was two times greater for the random compared to volunteer samples ($A62 vs $A31).


CONCLUSIONS
The estimated salt consumption derived from the two samples was comparable and was not substantively different to estimates obtained from other surveys. In countries where salt is pervasive and cannot easily be avoided, estimates of consumption obtained from volunteer samples may be valid and less costly.
The George Institute for Global Health, Sydney Medical School, The University of Sydney, Sydney, New South Wales, Australia.
Mary-Anne
MA
Land
Jacqui
J
Webster
Anthea
A
Christoforou
D
D
Praveen
Paul
P
Jeffery
John
J
Chalmers
Wayne
W
Smith
Mark
M
Woodward
Federica
F
Barzi
Caryl
C
Nowson
Victoria
V
Flood
Bruce
B
Neal
D000328:Adult; D001315:Australia; D002940:Circadian Rhythm; D003365:Costs and Cost Analysis; D005260:Female; D064368:Healthy Volunteers; D006801:Humans; D008297:Male; D008875:Middle Aged; D011897:Random Allocation; D017673:Sodium Chloride, Dietary / Q000008:administration & dosage* / Q000652:urine*; D016482:Urinalysis / Q000191:economics; D055815:Young Adult
D017673:Sodium Chloride, Dietary
Nutrition & Dietetics; Public Health