Aim: A study was undertaken to analyse the possible interaction between work environment and income for the probability of self-rated health being less than good.
Methods: Data from the Swedish Survey of Living Conditions for the years 1998 and 1999 were analysed. Employed 20- to 64-year-olds with a registered wage were included (n=5982). The synergy index (SI) was applied, using odds ratios from logistic regressions for men, women, and all. Low and high levels of physical demands, decision authority, skill discretion and psychological demands were separately combined with low- and high-wage income (median split). Full-time work and four sociodemographic factors were controlled for.
Results: Significant synergy was found for women when they were exposed to low income and a low level of skill discretion (SI=1.46 [1.01-2.13]), although this was attenuated by education level (SI=1.47 [0.96-2.25]). In general (both sexes), poor health caused by low income and unfavourable work is additive rather than multiplicatively exaggerating the risk among the jointly exposed.
Conclusion: Work exposures in the form of high physical load, low levels of decision authority and skill discretion, or a high level of psychological demands were significantly related to poor health also when income was high, suggesting that high income does not seem to buffer the detrimental effects of adverse working conditions. As nearly half of employed women were found to be in circumstances marked by synergy, it seems a relevant public health issue to improve these women's conditions at work, by simultaneously increasing, for example, job variety and wages.