In large epidemiologic studies, physical activity (PA) is often assessed using PA questionnaires (PAQ). Because available PAQ may not capture the full range of PA in which urban Chinese adults engage, a PAQ was developed for this purpose. We examined the validity of this PAQ and the 1-yr stability of PA in 545 urban Shanghai adults.
The PAQ was interview-administered twice, approximately 1 yr apart, and participants also wore an accelerometer and completed a PA-log for seven consecutive days every 3 months during the same year. The intraclass correlation coefficient (ICC) was used to evaluate the stability of PA across questionnaire administrations, and Spearman correlation coefficients (ρ) and mean differences and 95% limits of agreement were used to examine the validity of the questionnaire compared against accelerometry and the PA-log.
When measured by accelerometry, estimates of time spent in moderate-to-vigorous PA were lower and estimates of time spent sedentary were higher than when self-reported on the PAQ (P < 0.001). Total PA (ICC = 0.65) and PA domains (ICC = 0.45-0.85) showed moderate to high stability across PAQ administrations. Total PA (ρ = 0.30), moderate-to-vigorous activity (ρ = 0.17), light activity (ρ = 0.36), and sedentary behavior (ρ = 0.16) assessed by PAQ and by accelerometry were significantly and positively correlated, and correlations of the PAQ with the PA-log (ρ = 0.36-0.85) were stronger than those observed with accelerometry.
The PAQ significantly overestimated time spent in moderate-to-vigorous activity and underestimated time spent in light activity and sedentary behavior compared with accelerometry, but it performed well at ranking participants according to PA level.
1National Cancer Institute, Division of Cancer Epidemiology and Genetics, Bethesda, MD; 2MRC Epidemiology Unit, Institute of Metabolic Science, Cambridge, England, UNITED KINGDOM; 3Division of Epidemiology, Department of Medicine, Vanderbilt Epidemiology Center, Institute for Medicine and Public Health, Vanderbilt-Ingram Cancer Center, Vanderbilt University School of Medicine, Nashville, TN; 4Shanghai Cancer Institute, Shanghai, CHINA; and 5Department of Epidemiology and Preventive Medicine, University Medical Center Regensburg, GERMANY
Address for correspondence: Ulf Ekelund, MRC Epidemiology Unit, Institute of Metabolic Science, Box 285, Addenbrooke's Hospital, Hills Road,Cambridge, CB2 0QQ, England, United Kingdom; E-mail: email@example.com.
Submitted for publication August 2009.
Accepted for publication March 2010.