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Epidemiology:
doi: 10.1097/EDE.0b013e31826d08e4
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Comparing Ratings of Occupational Physical Activity

Boyle, Terry; Leong, Stacey

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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, terry.boyle@uwa.edu.au

Western Australian Institute for Medical Research, The University of Western Australia, Perth, Australia

Supported by a Project Grant (#572530) from the Australian National Health and Medical Research Council (BCEES). Supported by an Australian Postgraduate Award from The University of Western Australia and a scholarship from the Lions Cancer Institute of Western Australia (T.B.). supported by an Edwards and Patricia Usher Student Vacation Research Scholarship from The Cancer Council Western Australia (S.L.).

The authors report no conflicts of interest.

Supplemental digital content is available through direct URL citations in the HTML and PDF versions of this article (www.epidem.com). This content is not peer-reviewed or copy-edited; it is the sole responsibility of the author.

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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 (http://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 (http://links.lww.com/EDE/A612).

TABLE. Distributions...
TABLE. Distributions...
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Previous 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.

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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

terry.boyle@uwa.edu.au

Stacey Leong

Western Australian Institute for Medical Research

The University of Western Australia

Perth, Australia

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REFERENCES

1. Probert AM, Tremblay MP, Gorber SM. Desk potatoes: the importance of occupational physical activity on health. Can J Public Health. 2008;99:311–318

2. van Uffelen JG, Wong J, Chau JY, et al. Occupational sitting and health risks: a systematic review. Am J Prev Med. 2010;39:379–388

3. Ainsworth BE, Richardson MT, Jacobs DR Jr, Leon AS, Sternfeld B. Accuracy of recall of occupational physical activity by questionnaire. J Clin Epidemiol. 1999;52:219–227

4. Cust AE, Smith BJ, Chau J, et al. Validity and repeatability of the EPIC physical activity questionnaire: a validation study using accelerometers as an objective measure. Int J Behav Nutr Phys Act. 2008;5:33

5. U.S. Department of Labor. Dictionary of Occupational Titles. 19914th ed Washington, DC U.S. Government Printing Office

6. Longnecker MP, Gerhardsson le Verdier M, Frumkin H, Carpenter C. A case-control study of physical activity in relation to risk of cancer of the right colon and rectum in men. Int J Epidemiol. 1995;24:42–50

7. Slattery ML, Abd-Elghany N, Kerber R, Schumacher MC. Physical activity and colon cancer: a comparison of various indicators of physical activity to evaluate the association. Epidemiology. 1990;1:481–485

8. Moradi T, Nyrén O, Bergström R, et al. Risk for endometrial cancer in relation to occupational physical activity: a nationwide cohort study in Sweden. Int J Cancer. 1998;76:665–670

Cited By:

This article has been cited 1 time(s).

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10.1038/bjc.2013.310
CrossRef
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© 2012 Lippincott Williams & Wilkins, Inc.

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