Capture-recapture-adjusted prevalence rates of type 2 diabetes are relatedto social deprivation

We examined the prevalence of type 2 diabetes and social deprivation in one urban district in Liverpool from October 1995 to September 1996 inclusive, This area has a stable Caucasian population of 176,682. Lists were made of all known diabetics attending six different medical points of contact duri ng the year, and were condensed and aggregated to eliminate duplicates. Fro m postcode data, each patient was assigned to residence in one of the 14 el ectoral wards in the district, for which demographic structure and standard ized measures of social deprivation were known (Townsend index). The crude period prevalences of type 1 and type 2 diabetes were estimated for each wa rd. Crude prevalence data were then corrected by applying capture-recapture (CR) techniques to the different patient datasets to allow for undercount. The crude period prevalence (95%Cl) of diabetes was 1.5% (1.4-1.5%), or 25 85/176, 682. The mean age of people with diabetes was not significantly dif ferent between electoral wards. The crude period prevalence of type 2 diabe tes within individual wards ranged from 0.4% (0.3-0.6%) in the least depriv ed area to 4.1% (3.6-4.6%) in the most deprived area. The corresponding ran ge of CR-adjusted period prevalence rates of type 2 diabetes was from 3.2% (2.8-3.6%) to 6.7% (6.1-7.4%), and there was strong correlation between bot h crude and CR-adjusted prevalence and social deprivation in each ward (r=0 .76, p<0.001 for crude; and r=0.49, p<0.005 for CR-adjusted prevalence). Th ere was no correlation between the crude or CR-adjusted period prevalence r ates of type 1 diabetes and Townsend index (r=0.14, p=NS). This strong corr elation between the prevalence of type 2 diabetes and social deprivation ha s important implications for the planning of health-care delivery.