A comparison of the prevalence of rheumatoid arthritis and other rheumatic diseases amongst Pakistanis living in England and Pakistan.

The impact of environmental factors on the causation of rheumatoid arthritis (RA) is thought to be considerable. We explored this by comparing the prevalence of RA amongst Pakistanis living in England, where it is relatively high amongst ethnic English, and in Pakistan. The frequency of other rheumatic diseases was also compared. Information on 2056 adult Pakistanis in England and 4232 in Pakistan was obtained by house-to-house surveys using identical protocols. Positive respondents were examined by the same two clinicians in both countries. Rheumatic complaints increased with age and were more common in females in both communities. The standardized morbidity ratio (SMR) (95% CI) of RA in England was 2.1 (1.1-3.1) compared with Pakistan, a difference that was entirely attributable to females. The SMR (95% CI) for women was 3.0 (0.4-5.6) and for men 0.86 (-0.84 to 2.56). In Pakistan, there was a trend to more reporting of some but not all rheumatic complaints amongst the affluent segment of the population. This was increasingly apparent amongst those resident in England and the possibility of an impact of easier ascertainment amongst the more educated cannot be discounted. Low back pain was significantly more common in England. Furthermore, the colder climate was frequently invoked as a cause of more symptoms in England. Thus, several factors may have influenced the observation that RA is more common amongst Pakistanis in England compared with Pakistan. An environmental factor cannot be excluded. However, the frequency of non-specific musculoskeletal pain was similar. The regions of Pakistan from which the two populations were derived were also different and immunogenetic heterogeneity might also have contributed to the difference in RA prevalence.