Background/Purpose: Smoking is an established risk factor for rheumatoid arthritis (RA). A positive association between body mass index (BMI) and the risk of RA in women has been reported from several studies, but not from surveys of Scandinavian populations. Finally, a high serum cholesterol has been shown to predict RA in women, but not in men, possibly due to hormone related exposures. The objective of this study was to investigate the impact of described RA predictors in women in different age groups.

Methods: A total of 10902 women from a defined catchment area were included in a Preventive Medicine Program (PMP). Height and weight were measured as part of the health survey, and fasting blood samples were obtained. Serum total cholesterol (TC) was assessed by an enzymatic routine method. From this population, we identified individuals who developed RA after inclusion by linking the PMP register to the local community based RA register and to local and national patient administrative databases. In a structured review of the medical records, patients were classified according to the 1987 ACR criteria for RA. Four controls for each validated case, matched for sex, year of birth and year of screening, who were alive and free of  RA when the index person was diagnosed with RA, were selected from the PMP register. The impact of TC, BMI and smoking on the risk of RA was examined in conditional logistic regression models, stratified by age (tertile).

Results: 139 women were diagnosed with RA and fulfilled the ACR criteria after inclusion in the PMP. These pre-RA cases were compared to 556 matched controls. There was a significant positive association between TC and subsequent development of RA in the two younger age groups, but not in the oldest group (Table). Current smoking was associated with a significantly increased risk of RA in the youngest age group (women aged 29-48 years), whereas there was no association among those aged above 55. BMI did not predict RA in either of the subgroups.  

Conclusion: High cholesterol levels and smoking predict RA in an age dependent manner. The greater impact of these factors on the future risk of RA in younger women suggests that hormone related mechanisms contribute to the underlying pathways.