Trends in 24-h urinary sodium excretion in the United States, 1957-2003: a systematic review.

BACKGROUND Few studies have examined temporal trends in sodium intake in the US population. Collections of 24-h urine sodium excretions are reliable markers for dietary sodium intake. OBJECTIVE We examined temporal trends in 24-h urine sodium excretions to estimate temporal trends in sodium intake in the US population. DESIGN We performed a systematic search of English-language articles in MEDLINE for studies that reported collections of 24-h urine sodium excretions in the United States. We estimated mean urine sodium excretions over time for all studies and demographic subgroups. RESULTS We analyzed 38 studies, which dated from 1957 to 2003, and estimated a mean (± SE) 24-h urine sodium excretion per person of 3526 ± 75 mg Na. In a multivariate random-effects model with study year, sex, age, and race, the study year was not associated with any significant change in sodium excretions (coefficient = 154 mg Na · 24 h⁻¹ · 10 y⁻¹; 95% CI: -140, 448 mg Na · 24 h⁻¹ · 10 y⁻¹). In subgroup analyses, there was no significant temporal trend seen in male, female, black, or white study participants. CONCLUSION Sodium intake in the US adult population appears to be well above current guidelines and does not appear to have decreased with time.