The researchers investigated the spatial distribution of cases of primary biliary cirrhosis (PBC) in a defined region of North-East England.
The findings of the study were published in the December issue of Hepatology.
Some 770 patients with established PBC were identified in a previous comprehensive case finding study.
A total of 3044 control locations were randomly selected from postcode (zip code) data.
Geographical analysis was performed by testing both for spatial variation in risk and local clustering, by using previously described point process methods.
| PBC risk was higher in urban areas than in rural regions.
| Hepatology |
Both tests used the same null hypothesis that risk of disease does not vary spatially and cases occur independently of each other.
The researchers found statistically significant spatial variations in risk in the whole study region, and in the major urban area within the region.
Risk was higher in the urban area of Tyneside, England, than in the surrounding rural area.
Within the rural area, spatial variation in risk was equivocal, but there was significant clustering of cases (average cluster effect approximately 10 excess cases within a 7-km radius).
PBC occurred to a density of 10.7 cases/km2 in the highest risk areas.
Martin I. Prince, of the Center for Liver Research at the Newcastle Medical School, concluded on behalf of his colleagues, "PBC is unevenly distributed in North-East England. This may reflect one or more environmental risk factors in its etiology."