Social deprivation and bacterial meningitis in north east thames region: three year study using small area statistics

Introduction

The rates of many diseases are linked to the deprivation of the area.1 Earlier British studies have shown that lower social class and overcrowding are associated with increased risk of meningococcal meningitis.2 Using data from a prospective study in North East Thames region (now part of North Thames region) between 1991 and 1993 we examined the relation between types of bacterial meningitis3 and deprivation of residential area, looking at rates specific for age and ethnic group.

Subjects, methods, and results

Between 1991 and 1993, 369 cases of bacterial meningitis (177 due to Neisseria meningitidis; 103 to Haemophilus influenzae; 89 to Streptococcus pneumoniae) were recorded in North East Thames and had postcode data available (representing 89% of all cases collected). Deprivation was measured by Townsend score4 and levels of overcrowding in the ward of residence and linked to cases by postcodes. The eight cases of H influenzae meningitis which occurred after the introduction of routine infant immunisation in 1993 were excluded.

North East Thames wards were ranked according to Townsend score and divided into three groups, with an equal number of wards in each group (labelled most deprived, intermediate, least deprived), the group formed from wards with the highest Townsend score being classified as most deprived. This process was repeated for overcrowding. Rates (per 100 000 per year) for the three causes of meningitis were calculated for each group, using the number of cases over two years (H influenzae) or three years (N meningitidis and S pneumoniae) as the numerators and unadjusted 1991 census population as the population base. The χ² test and χ² test for trend were calculated, using EpiInfo version 6 to determine the relation between disease rates and deprivation or overcrowding. We focused on children aged 0-4 years because the three major causes of bacterial meningitis are most common in children aged under 5 years.

Overall, rates for meningococcal meningitis were 74% higher in overcrowded areas (table 1). H influenzae meningitis was not associated with deprivation or overcrowding. Rates for pneumococcal meningitis were approximately twice as high in the most deprived wards and the most overcrowded wards. In white children under 5 years, rates for meningococcal meningitis were over twice as high in the most overcrowded wards than in the least overcrowded wards. By using the same methods we found that pneumococcal meningitis rates were significantly higher among white people of all ages in the most deprived wards (0.9/100 000 v 0.4/100 000 in least deprived wards).

Comment

In spite of the difficulties with ascribing socioeconomic characteristics of geographic areas to individuals living in those areas,5 we believe that these data show that rates of meningoccocal and pneumococcal meningitis are related to measures of area deprivation. Though the small numbers involved may have had an effect in terms of the power of our study, our analysis allowed an internal comparison of effects on the rates of the three main causes of bacterial meningitis. Their similar epidemiology in preschool children led us to believe they would behave similarly with respect to overcrowding and poverty. However, relations between deprivation and rates of these three diseases differed. Studies collecting sociodemographic data at individual and area levels could clarify the basis for these differences. Our findings suggest that effective action to tackle social deprivation will have an effect on rates of bacterial meningitis.