24USE - 24 Hour Urinary Sodium Excretion Survey


Overview


A sub-study of PURE, 24USE aims to examine the salt intake of Canadians and how this relates to risk factors for heart disease and stroke. It will also look at the relationship between salt intake and lifestyle, environmental and genetic factors. Vancouver is one of the four centres in Canada to be taking part in this study; the others are Hamilton, Ottawa and Quebec City. Results will assist planning efforts towards the development and implementation of appropriate guidelines, interventions, programs, and policies that may prevent heart disease and stroke in the future.


Background


Sodium intake is related to the development of high blood pressure, which is a frequent major risk factor for cardiovascular disease and other morbidities. A population-preventive approach may be beneficial to reducing salt intake, but should be based upon sound data on sodium levels from urinary excretion in a large sample. Such a study does not exist in Canada but has been conducted successfully in the UK and Finland.


Objectives


In a large sample of urban and rural adult men and women, we aim to determine:

  • 1. overall sodium intake using 24-hour urinary sodium excretion (USE),
  • 2. if the 24-hour USE is a reliable biophysical measure of dietary sodium,
  • 3. if a fasting first morning urine (FMU) and a pre-dinner urine (PDU) are good estimates of 24-hour USE and potassium excretion,
  • 4. the association between the 24-hour USE and various cardiovascular risk factors (hypertension, diabetes, obesity, smoking status, age, sex, diet, physical activity) and socioeconomic status,
  • 5. the prevalence of iodine deficiency among Canadian adults.

Methodology


A total of 1,600 PURE participants will be used for this study. At each centre, 400 (200 urban, 200 rural) consecutive consenting participants will submit a 24 hour urine sample. PABA pills are administered to eligible participants to determine urine collection completeness, and simple questionnaires are administered to assess dietary sodium intake. 50 participants are also asked to collect a pre-dinner and fasting morning sample, while 100 are asked to repeat collection in the following 15 to 45 days to estimate variability. Urine containers are collected within 12 hours of completion, and biochemical measures (Na, K, iodine, creatinine and eGFR) are obtained. Participant information is also collected in the form of: medical history (including medication), lifestyle status (diet, exercise, smoking status), socioeconomic status, blood pressure, and anthropometric measures (weight, height, waist and hip circumference).


Progress to Date


Recruitment for this study started in February 2012 and is expected to last 18 months.