Geographical epidemiology of residence of patients with motor neuron disease in Lancashire and south Cumbria

Abstract

Objectives: To seek objective evidence for geographical clustering of places of residence of patients with motor neuron disease (MND).

Methods: A complete residential history from birth to onset of disease was obtained from a cohort of 130 patients with MND from Lancashire and south Cumbria presenting to the Department of Neurology in Preston between 1 January 1989 and 31 December 1993. These data were compared with population based reference data from the 1991 UK Census.

Results: Some areal units showed a greater, others a lesser, number of MND patient residences than expected. The results suggest that the background population incidence of MND is relatively low and that the overall incidence figures previously quoted have been skewed upwards by areas in which the incidence of MND is relatively increased. These findings were further tested by Poisson modelling. The Poisson model provided a poor fit for the data at postcode district and sector levels confirming that patients with MND were significantly more likely to have lived in some areas than others after allowing for variation in population of the different areal units and for variation in duration of residence.

Conclusions: These findings reinforce the results of previous work, much of which has been qualitative rather than quantitative. The results presented here suggest a low background incidence of MND in the context of generally quoted overall incidence figures. This low background incidence is, however, skewed upwards by some areal units with a relatively high incidence, thus achieving overall incidence rates comparable with generally quoted figures. We conclude that there is prima facie evidence of spatial patterns in the distribution of places of residence of patients with MND. Further examination of occupational and environmental factors in the lives of the patients with MND is required to obtain a better understanding of the importance of these findings.