Occupational physical activity and non-Hodgkin's lymphoma

Purpose: The purpose of this study was to evaluate the role of physical act ivity in the development of non-Hodgkin's lymphoma (NHL). Methods: Incident NHL cases and population-based controls were identified from three case-co ntrol studies conducted in four midwestern states: Iowa, Kansas, Minnesota, and Nebraska,A total of 1177 cases (993 men, 184 women) and 3625 controls (2918 men, 707 women) were interviewed. Usual occupation (all states) and l ifetime occupational histories (Iowa and Minnesota only), obtained from int erviews, were classified for energy expenditure (EE) and sitting time. Odds ratios (QR) and 95% confidence intervals were calculated comparing moderat e and high activity levels with sedentary levels. Results: There was no evi dence of an association between NHL and occupational physical activity meas ured either by EE or sitting time. Among men, the OR associated with usual occupation moderate and high EE were 1.1 and 1.0, respectively. For sitting time the OR were also 1.1 and 1.0 for moderate and hi,oh activity, respect ively. Among women, slight nonsignificant elevations in risk of NHL were ob served among the high energy level and high activity sitting categories. Th e trends were not significant; There was no evidence of confounding or effe ct modification by vital status, hair dye use, or solvent exposure. Among s ubjects with lifetime occupational histories, there were no significant inc reases or trends for cumulative or average EE or sitting time. There was no association between occupational physical activity and NHL. Conclusion: Re search on nonoccupational physical activity, which in the U.S. is likely th e more important component of daily activity than occupational activity, ma y still be warranted given the laboratory evidence linking physical activit y and immune function, an important factor in the etiology of NHL.