Inequalities in rates of gonorrhoea and chlamydia between black ethnic groups in south east London: cross sectional study

Objectives: To examine differences in population based rates of gonorrhoea and chlamydia between black ethnic groups in Lambeth, Southwark and Lewisha m Health Authority. Methods: Episodes of gonorrhoea or chlamydia recorded among attenders at 11 genitourinary clinics in south and central London from 1 January 1994 to 3 1 December 1995 were retrieved. Complete: data on chlamydia were only avail able fur women. Ethnic group was assigned according to census categories-wh ite, black Caribbean, black African, black other, Asian, or other. We calcu lated yearly incidence rates for episodes of gonorrhoea and chlamydia in re sidents of Lambeth, Southwark and Lewisham Health Authority. Random effects Poisson regression models were used to examine associations between infect ion rates and age, ethnic group, and material deprivation. Results: During the study period there were 1994 episodes of gonorrhoea in men and women and 1376 episodes of chlamydia in women with complete data. F or both infections rates among individuals from black Caribbean and black o ther ethnic groups were markedly higher than among black Africans. In men, the gonorrhoea rate among black Caribbean 20-24 year olds was 2348 (95% CI 1965 to 2831) episodes per 100 000 compared with 931 (95% CI 690 to 1288) i n black African men and 111 (95% CI 100 to 124) per 100 000 in white men of the same age. Among women gonorrhoea rates were highest in black Caribbean 15-19 year olds (2612, 95% CI 2161 to 3190 per 100 000). In contrast, rate s in black African women of the same age (331, 95% CI 154 to 846 per 100 00 0) were similar to those of white women (222, 95% CI 163 to 312). Chlamydia rates were also highest in black Caribbean 15-19 year old women (4579, 95% CI 3966 to 5314 per 100 000), compared with 1286 (95% CI 907 to 1888) in b lack African and 433 (95% CI 349 to 544) per 100 000 white women. Controlli ng for material deprivation and age only attenuated differences in rates be tween ethnic groups slightly. Conclusions: There are marked differences in rates of gonorrhoea and chlamy dia between different black ethnic groups, with higher rates in black Carib beans than black Africans. This study supports the hypothesis that assortat ive sexual mixing patterns can restrict epidemics of sexually transmitted i nfections within ethnic groups. Differences in disease occurrence between b lack ethnic groups should be explored before combining data, even when numb ers of episodes are small.