MedicalResearch.com: What is the background for this study?
Response: Studies have shown that there is a strong linear relationship between sodium intake and blood pressure and raised blood pressure is a leading cause of death and disability worldwide.
The current mean population sodium intake among adults in most countries is approximately 4,000 mg/d (10 g/d salt). The World Health Organisation (WHO) has recommended a 30% reduction in sodium intake by 2025 with an eventual target of less than 2,000 mg/d (5 g/d salt) for all countries. Several recent cohort studies have challenged the WHO’s recommendations, as these studies suggested that there was a J or U-shaped relationship between sodium and risk, i.e. lower and higher sodium intake both were associated with an increased risk of cardiovascular events and deaths.
However, these studies have several severe methodological problems, one of which is the use of a biased or unreliable estimate of individual’s usual sodium intake, e.g. a single spot urine with the Kawasaki formula.
Our study, for the first time, has compared the relationship of sodium intake and mortality, based on various methods to assess usual sodium intake, including estimates based on the Kawasaki formula (single and average of multiple days) and a single measured 24-hour urine, with the gold standard method, i.e. the average of multiple non-consecutive measured 24-h urines.