Comparing Ratings of Occupational Physical Activity

Abstract

To the Editor: Occupational physical activity and inactivity have been associated with a range of health outcomes.1,2 There are several ways in which occupational physical activity can be measured. One commonly used method classifies occupational activity based on job title. This method is thought to have limitations3; however, and there is little research about how it compares to more valid and reliable measures of occupational activity. We compared occupational activity based on job title and job duties with self-reported occupational activity. Participants included in this study were 765 women who took part in a case-control study of breast cancer (The Breast Cancer Environment and Employment Study) in Western Australia between November 2009 and October 2010 and fully completed the occupational activity section of the questionnaire. The study was approved by the Human Research Ethics Committees at the University of Western Australia and the Western Australian Department of Health. For each job held for >6 months, participants were asked to record various details including how much physical activity the job required. Participants could choose from one of four activity categories: sedentary (sitting), standing, manual, and heavy manual. Previous research suggests that this method has acceptable validity and reliability.4 Each job was also classified into one of five categories (sedentary, light, medium, heavy, and very heavy) of Physical Demands Strength Rating, based on job title and duties.5 The heavy and very heavy categories were combined, as there were few “very heavy” jobs. The self-reported sedentary, standing, manual, and heavy manual categories were considered to be equivalent to the sedentary, light, medium, and heavy Physical Demands Strength Ratings, respectively. More information about the two methods is given in eTable 1 (https://links.lww.com/EDE/A612). We used quadratic-weighted kappa to assess agreement between the two methods for all jobs, currently held positions, and lifetime occupational activity level (determined by calculating which occupational activity category a participant spent the greatest amount of time in over their working lifetime). All statistical analyses were conducted using Stata 11.0 (StataCorp, College Station, TX). The participants’ characteristics and their lifetime occupational activity levels (for each of the two measures) are shown in the Table. The participants held a total of 4503 jobs (median = five jobs), and 484 participants had a current job. There was good overall agreement between the two methods when rating all jobs (kappa = 0.73 [95% confidence interval = 0.71–0.74]), with 72% of the 4503 jobs rated the same on both methods. For currently held jobs, 70% of the 484 jobs were rated the same on both methods (kappa = 0.70 [95% confidence interval = 0.64–0.75]). There was also good agreement between the two methods when classifying participants into a lifetime occupational activity level; 70% of the 765 participants received the same rating on both methods (kappa = 0.67 [95% confidence interval = 0.62–0.71]). Cross-tabulations of the ratings from the two methods for all jobs, current jobs and lifetime occupational activity level are shown in eTables 2–4 (https://links.lww.com/EDE/A612).TABLE: Distributions of Various Demographic Characteristics, by Lifetime Occupational Activity Level, as Categorized by Self-Reported Occupational Physical Activity or Job-Title/Duties-Based Occupational Activity, of the 765 Participants in the Breast Cancer Environment and Employment Study, Western Australia, 2009–2010Previous research in this area has found fair-to-moderate agreement between self-reported occupational activity and job-title-based occupational activity among both men6,7 and women.7,8 Our results suggest that studies lacking self-reported occupational activity, but having some information about job title/duties, may nonetheless be useful for investigating associations among occupational physical activity, occupational sitting, and health outcomes in women. ACKNOWLEDGMENTS The authors thank Lin Fritschi, Jane Heyworth, and Fiona Bull for their critical reviews of the manuscript. Terry Boyle Western Australian Institute for Medical Research The University of Western Australia Nedlands, Western Australia, Australia School of Population Health The University of Western Australia Perth, Australia [email protected] Stacey Leong Western Australian Institute for Medical Research The University of Western Australia Perth, Australia