Geographical variation in anophthalmia and microphthalmia in England, 1988-94

Objective: To investigate the geographical variation and clustering of congenital anophthalmia and microphthalmia in England, in response to media reports of clusters. Design: Comparison of pattern of residence at birth of cases of anophthalmia and microphthalmia in England in 1988-94, notified to a special register, with pattern of residence of all births. Three groups studied included all cases, all severe cases, and all severe cases of unknown aetiology. Outcome measures: Prevalence rates of anophthalmia and microphthalmia by region and district, and by ward population density and socioeconomic deprivation index of enumeration district grouped into fifths. Clustering expressed as the tendency for the three nearest neighbours of a case to be more likely to be cases than expected by chance, or for there to be more cases within circles of fixed radius of a case than expected by chance. Results: The overall prevalence of anophthalmia and microphthalmia was 1.0 per 10 000 births. Regional and district variation in prevalence did not reach statistical significance. Prevalence was higher in rural than urban areas: the relative risk in the group of wards of lowest population density compared with the most densely populated group was 1.79 (95% confidence interval 1.15 to 2.81) for all cases and 2.37 (1.38 to 4.08) for severe cases. There was no evidence of a trend in risk with socioeconomic deprivation. There was very little evidence of localised clustering. Conclusions: There is very little evidence to support the presence of strongly localised environmental exposures causing clusters of children to be born with anophthalmia or microphthalmia. The excess risk in rural areas requires further investigation.

研究目标：针对媒体报道的聚集性病例事件，探究英格兰地区先天性无眼症和小眼球症（congenital anophthalmia and microphthalmia）的地理分布差异与聚集特征。研究设计：将1988-1994年英格兰地区上报至专项登记册（special register）的先天性无眼症和小眼球症病例的出生时居住地址分布，与全活产婴儿的居住地址分布进行对比。本研究纳入三组分析对象：所有病例组、所有重症病例组，以及病因不明的重症病例组。结局指标：按区域、行政区，以及按普查区（enumeration district）划分的人口密度五分位组与社会经济剥夺指数五分位组，分别统计先天性无眼症和小眼球症的患病率。聚集性的评估方式为：病例的最近3个邻近个体发生病例的概率是否高于随机预期水平，或是病例周围固定半径范围内的病例数是否多于随机预期水平。研究结果：先天性无眼症和小眼球症的总体患病率为每10000活产儿1.0例。患病率在区域与行政区层面的差异未达到统计学显著性。农村地区的患病率高于城市地区：与人口密度最高的街区组相比，人口密度最低的街区组的相对风险，在所有病例组中为1.79（95%置信区间（confidence interval）1.15~2.81），在重症病例组中为2.37（1.38~4.08）。未发现风险随社会经济剥夺指数呈现趋势性变化。几乎不存在局域聚集性的相关证据。研究结论：几乎没有证据表明存在强局域性的环境暴露因素，导致先天性无眼症和小眼球症患儿的聚集性出生。农村地区的超额风险仍需进一步探究。