Comorbidity and lifestyle, reproductive factors, and environmental exposures associated with rheumatoid arthritis

Abstract

Objective-To evaluate the influence of lifestyle, reproduction, and some external factors on the development of rheumatoid arthritis (RA) and to describe its comorbidity. Methods-Cases were identified retrospectively from 1980 to 1995 at the University Hospital in Linköping, Sweden. The study comprised 422 cases and 859 randomly selected population referents. Data on possible aetiological factors and comorbidity were collected by postal questionnaire. Results-The response rates were 67% among cases and 59% among referents. A decrease in the occurrence of atopic allergy was seen in the cases (odds ratio (OR) 0.6, 95% confidence interval (CI) 0.4 to 1.0). There was a positive association between RA and insulin treatment (OR 10.2, 95% CI 1.7 to 60.8) in women, and women with a short fertile period had an increased risk of RA (OR 2.5, 95% CI 1.1 to 5.4). Current and previous smoking were associated with increased risks for RA in both sexes, and in men a dose-response relationship was found with number of tobacco pack years (p for trend <0.005). The risk for RA decreased with increasing level of education in both men and women. Increased risks were seen in men born into households with private wells (OR 2.8, 95% CI 1.5 to 5.2), residentially exposed to mould (OR 4.6, 95% CI 1.1 to 20.2), or exposed to farm animals (OR 3.3, 95% CI 0.7 to 16.6). In women there were positive associations between RA and reporting a previous joint injury (OR 2.5, 95% CI 1.0 to 6.6) and prolonged exposure to hair dyes (OR 1.9, 95% CI 0.8 to 4.5). Conclusions-RA, a disease with features of T helper 1 (Th1) dominated immune response, was inversely associated with atopic allergy, a Th2 dominated condition, while there were indications of a strong positive association with Th1 related diabetes mellitus. The results support a causal relationship between smoking and RA. The level of education was inversely associated with RA, while there was a positive association between RA and certain residential factors in men and a short fertile period in women.

Impact of smoking as a risk factor for developing rheumatoid arthritis: a meta-analysis of observational studies

“…Smoking rates of ever, current and past were 50.6%, 26.5% and 26.3%, respectively. In the 11 case–control studies,8 9 11 12 18 19 20 21 22 34 35 36 4764 cases and 13 647 controls were included, and in five cohort studies,5 7 10 37 38 9121 cases were identified from among 566 044 participants. Seven case–control studies and one cohort study of male subjects and nine case–control and five cohort studies of female subjects were included.…”

“…In the seven case–control studies11 18 19 20 21 22 35 36 the summary OR for ever, current and past smokers were 1.87 (1.53 to 2.29), 1.89 (1.49 to 2.40) and 1.79 (1.34 to 2.38). Differences in smoking status were not significant.…”

“…The first is a stronger influence of smoking on developing RA in men, and the second is the association of smoking with rheumatoid factor (RF) positive RA in men, but not in women 7 18. However, the findings for women of various studies have been inconsistent 7 18 19 20 21 22. Moreover, although several reviews have dealt with the relation between smoking and the development of RA, no systematic analyses have been conducted 23 24 25 26 27 28…”

Diabetes preventive gluten‐free diet decreases the number of caecal bacteria in non‐obese diabetic mice

“…This seems to be in contrast to our results in which diabetes prevention was associated with a decrease in Lactobacillus spp. While allergies and IBD are characterized by Th2 responses, T1D is associated with Th1 immune responses [41]. Interestingly, neonatal antibiotic treatment may skew the Th1 immune response towards a Th2 profile, an effect that can be reduced by supplementation of Gram-positive, microaerophilic bacteria [42].…”

Risk factors for rheumatoid arthritis

“…A dose-response gradient, however, has been suggested in three studies (82,84,87). Such a monotonic relation between exposure and outcome supports causality, but its absence is not falsifying.…”