PHYSICAL ACTIVITY PARTICIPATION AND THE VALIDITY OF SELF-REPORTED WEIGHT AND HEIGHT IN WOMENLM Mudd, J Osuch, W Karmaus, JM Pivarnik, FACSM. Center for Physical Activity and Health, Michigan State University, East Lansing, MI.
BACKGROUND: Self-reported weight and height are often used in epidemiological studies, although validity may be limited. Weight status is known to influence the validity of self-reported anthropometric variables in women; but the effects of demographic and health behavior variables have not been well defined.
PURPOSE: To examine how physical activity (PA) and demographic/health variables affect the validity of self-reported height, weight, and body mass index (BMI) among women 18-65 yrs old.
METHODS: Women (n=138) self-reported weight (lbs), height (in), and demographic/health variables during a telephone interview on reproductive health and diet. A trained investigated later measured weight on an electronic scale, height with a portable stadiometer, and minutes of moderate and/or vigorous PA/wk with the 7-day PA recall questionnaire during a home visit. Quartiles of total min/wk of PA were created and the number of women reporting any participation in vigorous PA was determined. BMI values were calculated (kg•m -2) using self-reported and measured data. Overweight was defined as BMI ≥25 kg•m -2. Measured values for height, weight, and BMI were used as the criterion.
RESULTS: Mean difference between self-reported and measured height was 0.05 in (95% CI, -0.07; 0.18), whereas mean differences in weight and BMI values were -4.43 lb (-5.55; -3.30) and -0.79 kg•m -2 (-1.01;-0.57). Overweight women (n=73) and those reporting no vigorous PA (n=45) underestimated weight to a greater degree than normal weight, vigorously active women (p values <0.05). Vigorous PA participation added significantly to the prediction of measured BMI from self-reported BMI. For self-reported data the sensitivity of overweight status was 0.81 (95%CI, 0.70; 0.89) and specificity was 1.00 (0.83; 1.00). When adjusted for vigorous PA, sensitivity increased to 0.85 (0.74; 0.92), but specificity decreased to 0.95 (0.86-0.99). Total PA quartile, age, marital status, education, working status, depression, alcohol use, and smoking did not influence these results.
CONCLUSION: Women report height accurately; however the validity of self-reported weight and BMI values varies by current weight status and vigorous PA participation. The sensitivity of self-reported data for detecting overweight is improved by controlling for vigorous PA participation.
