Multiple sclerosis in Tayside, Scotland: detection of clusters using a spatial scan statistic

Area of Science:

• Epidemiology
• Neurology
• Public Health

Background:

• The aetiology of multiple sclerosis (MS) is debated, with ongoing discussion regarding the relative importance of genetic factors versus infectious agents.
• Identifying spatial and temporal clusters of MS can provide evidence for the role of infectious agents in genetically susceptible populations.

Purpose of the Study:

• To detect and analyze spatial and temporal clusters of multiple sclerosis (MS) in the Tayside region of Scotland.
• To investigate the potential contribution of exogenous factors to MS distribution by examining disease clusters.

Main Methods:

• Utilized a spatial scan statistic on a population-based MS register for Tayside, Scotland (1970-1997).
• Accounted for age at symptom onset, gender, population density, and social deprivation in the analysis.
• Analyzed 772 MS cases, with a mean age of onset of 35.7 years and 73.8% female cases.

Main Results:

• A significant temporal cluster of MS was identified across the Tayside region between 1982 and 1995 (P = 0.002).
• A significant spatial cluster was detected from 1993 to 1995, centered in a rural area southwest of Perth (P = 0.016).
• An overall increase in MS cases over time was observed, potentially due to improved detection and diagnosis.

Conclusions:

• The identified significant temporal and spatial-temporal clusters suggest that exogenous factors play a role in the distribution of MS in Tayside.
• These findings support the hypothesis that infectious agents may contribute to the aetiology of MS in genetically susceptible populations.