Occupational Physical Activity, Overweight, and Mortality: A Follow-Up Study of 47,405 Norwegian Women and Men
Graff-Iversen, Sidsel, Selmer, Randi, Sorensen, Marit, Skurtveit, Svetlana, Research Quarterly for Exercise and Sport
This population-based 24-year follow-up study evaluated the association of occupational physical activity (OPA) with overweight and mortality in 47,405 men and women, healthy at baseline, and reporting OPA as sedentary (reference), light, moderately heavy, or heavy. The adjusted odds ratio for overweight was slightly less than 1 for all categories of current nonsedentary work in men but increased by OPA in women. Only heavy OPA conferred a lower mortality with an adjusted rate ratio of 0.84 (95% confidence interval, 0.76-0.92) for men and 0.69 (95% confidence interval, 0.52-0.91) for women. This observational study, with OPA recorded in the 1970s and 1980s, suggested a slight protective effect for overweight by nonsedentary work for men and lower mortality by heavy OPA for both genders.
Key words: body mass index, cardiovascular disease, exercise, physical work
In the 1960s and 1970s, occupational physical activity (OPA) was considered important in preventing cardiovascular disease (CVD) and coronary heart disease (CHD) in particular (Leon & Blackburn, 1983). Some studies showed a protective effect (Keys, 1980; Paffenbarger & Hale, 1975), but others found no or positive associations of OPA with CVD risk factors, incidence, or mortality (Holme, Helgeland, Hjermann, Leren, & Lund-Larsen, 1981; Kannel, Belanger, D'Agostino, & Israel, 1986; Kristal-Boneh, Harari, Melamed, & Froom, 2000; Lochen & Rasmussen, 1992; Rosengren & Wilhelmsen, 1997; Stender, Hense, Doring, & Keil, 1993). Many of those studies highlighted problems related to measurement of exposure to OPA and confounding effects by social factors and lifestyle. In contrast, high levels of leisure-time physical activity (LPA) has most often been found to imply a lower CVD and all-cause mortality (Holme et al., 1981; Kannel et al., 1986; Lissner, Bengtsson, Bjorkelund, & Wedel, 1996; Rosengren & Wilhelmsen, 1997; Barengo et al., 2004). The increasing prevalence of obesity has prompted a new concern for associating OPA with body weight and related health outcomes (Fogelholm, Mannisto, Vartiainen, & Pietinen, 1996; Hu et al., 2003; Meyer & Tverdal, 2005).
Sedentary work is now common, and the reduction in energy spent at work may be an important contributor to the obesity epidemic among adults (Fogelholm, Mannisto, Vartiainen, & Pietinen, 1996). Cross-sectional data suggest a protective effect of OPA with respect to overweight in middle-aged Norwegian men, at least in some geographical areas (Graff-Iversen, Skurtveit, Sorensen, & Nybo, 2001). Prospective studies have found that brisk walking is associated with substantial reduction in CVD incidence (Tanasescu et al., 2002; Manson et al., 2002), whereas anaerobic work, such as lifting, may increase the risk (Fransson et al., 2004). On this basis, we wanted to study the associations between OPA and overweight in cross-sectional and follow-up data and between OPA, CVD, and total mortality, taking gender, LPA, smoking and other known CVD risk factors, occupation, geography, education, and income into account.
During 1974-78, cardiovascular health surveys were conducted in three mostly nonurban counties in Norway: Finnmark in the north, Sogn og Fjordane on the western coast, and Oppland in the southern inland (Bjartveit, Foss, Gjervig, & Lund-Larsen, 1979). A health examination was offered to all inhabitants ages 35-49 years. Response to the survey varied from 79% to 88% for men and 86% to 93% for women. A similar survey was conducted in 1985-88, with 67% attendance. At both occasions, the participants completed a questionnaire, reporting on known CVD, diabetes mellitus, and anti-hypertensive therapy. Also, information about smoking, dietary habits, LPA, OPA, disability pension, and domestic work was collected.
Physical Activity. OPA and LPA were measured with instruments developed in Gothenburg, Sweden, in the 1960s (Saltin & Grimby, 1968; Wilhelmsen et al. …