Associations among blood pressure, salt consumption and body weight status of students from south-western Ontario

OBJECTIVE: The purpose was to examine the associations among body weight status, blood pressure and daily Na intake among grade 7 students from south-western Ontario, Canada. DESIGN: Cross-sectional. Data were collected using the Food Behaviour Questionnaire, including a 24 h diet recall. Measured height and weight were used to determine BMI. Blood pressure was taken manually using mercury sphygmomanometers. SETTING: Twenty-six schools in south-western Ontario, Canada. SUBJECTS: Grade 7 students (n 1068). RESULTS: Body weight status indicated 1 % were underweight, 56 % normal weight, 23 % overweight and 20 % were obese. Mean systolic blood pressure (SBP) and diastolic blood pressure (DBP) were 108·3 (sd 10·3) mmHg and 66·0 (sd 7·5) mmHg, respectively, and mean Na intake was 2799 (sd 1539) mg/d. Bivariate analyses suggested that SBP (P < 0·001) and DBP (P < 0·001) were significantly different by body weight status, yet no associations were observed for Na. Adjusted for gender, ethnicity and under-reporting, participants were more likely to be overweight/obese if they had higher SBP (v. lower: OR = 1·06, 95 % CI 1·05, 1·08, P < 0·001), higher DBP (v. lower: OR = 1·02, 95 % CI 1·00, 1·04, P = 0·043) and higher intakes of Na (3rd v. 1st quartile: OR = 1·72, 95 % CI 1·14, 2·59, P = 0·009; 4th v. 1st quartile: OR = 2·88, 95 % CI, 1·76, 4·73, P < 0·001). CONCLUSIONS: High intakes of Na, coupled with high SBP and DBP, were associated with overweight and obesity status among the grade 7 sample from south-western Ontario, Canada.