Original Article Occupational Class Differences in Body Mass Index and Weight Gain in Japan and Finland

Copyright © 2013 Karri Silventoinen et al. This is an open access article distributed under the terms of Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original author and source are credited. Background: Occupational class differences in body mass index (BMI) have been systematically reported in developed countries, but the studies have mainly focused on white populations consuming a Westernized diet. We compared occupational class differences in BMI and BMI change in Japan and Finland. Methods: The baseline surveys were conducted during 1998–1999 among Japanese (n = 4080) and during 2000–2002 among Finnish (n = 8685) public-sector employees. Follow-up surveys were conducted among those still employed, in 2003 (n = 3213) and 2007 (n = 7086), respectively. Occupational class and various explanatory factors were surveyed in the baseline questionnaires. Linear regression models were used for data analysis. Results: BMI was higher at baseline and BMI gain was more rapid in Finland than in Japan. In Finland, baseline BMI was lowest among men and women in the highest occupational class and progressively increased to the lowest occupational class; no gradient was found in Japan (country interaction effect, P = 0.020 for men and P < 0.0001 for women). Adjustment for confounding factors reflecting work conditions and health behavior increased the occupational class gradient among Finnish men and women, whereas factors related to social life had no effect. N