Climatic factors in the development of radiographic hand osteoarthritis

A study was undertaken to evaluate whether various ethno-territorial samples have different characteristics of radiographic hand osteoarthritis (OA) and to evaluate whether climate is associated with differences in hand OA characteristics. The total sample included 4775 individuals (2220 males and 2555 females), belonging to 12 sub-samples, including 9 ethnic groups, from 10 geographic locations in the former USSR. Ethnicity, latitude, longitude, and climatic parameters (mean temperatures, humidity, and day length of January and July) were collected for each sample. X-rays of the left hand were obtained from each individual. Prevalence of hand OA was evaluated in four age groups (36-40, 41-45, 46-50, and 51-55 years). Using maximum likelihood estimation, the following characters were determined: the mean age of persons having 1 and 5 affected joints-A_m1 and A_m5, and the mean time in which one additional joint was affected-T_m. The difference between samples was evaluated using the χ²-test. The associations between hand OA, and climate were evaluated using Pearson's correlations. Significant differences in OA characteristics among samples were found. Prevalence of hand OA in the age-group 46-50 showed significant association with longitude (r=0.57, p=0.05) and inter-seasonal temperature amplitude (r=0.77, p=0.0035) and significant negative association with mean temperature of January (r=-0.72, p=0.0089). Significant associations were found between longitude, the mean temperature of January, and inter-seasonal temperature amplitude and age-related hand OA parameters (A_m1 and A_m5). The present study indicates that the differences in characteristics of radiographic hand OA among samples are most likely associated with climatic variation.