Owens J R, Harris F, Walker S, McAllister E, West L
J Med Genet. 1983 Apr;20(2):90-3. doi: 10.1136/jmg.20.2.90.
The incidence of Down's syndrome in the Liverpool and Bootle areas from 1961 to 1979 was investigated. A total of 319 liveborn cases was ascertained over this period. Using 3-year moving averages, the incidence of the condition fell gradually from 1.62 per 1000 livebirths for 1961 to 1963 to 1.09 per 1000 livebirths for 1977 to 1979. This trend is significant at the 0.1% level. Over the same period the mean maternal age of Down's syndrome births fell gradually from 36.7 years in 1961 to 29.0 years in 1979. This trend is significant at the 1% level. There was a contemporaneous decrease in the proportion of total births to women over 35 years in the study area. Cytogenetic analysis was performed on 175 out of the 319 index cases (54.9%). Of these, there were 161 trisomies (92%), 11 translocations (6.3%), and three mosaics (1.7%). Between 1969 and 1979 four terminations of pregnancy for Down's syndrome were performed, all for trisomy. Quinquennial age specific incidences for Down's syndrome were calculated for the years 1960 to 1964, 1965 to 1969, 1970 to 1974, and 1975 to 1979. There have been no statistically significant changes over this time. It is suggested that the fall in incidence of Down's syndrome can be explained by the fall in mean maternal age.
对1961年至1979年利物浦和布特尔地区唐氏综合征的发病率进行了调查。在此期间共确诊了319例活产病例。采用3年移动平均值，该病的发病率从1961年至1963年的每1000例活产1.62例逐渐下降至1977年至1979年的每1000例活产1.09例。这种趋势在0.1%的水平上具有显著性。同期，唐氏综合征患儿母亲的平均年龄从1961年的36.7岁逐渐下降至1979年的29.0岁。这种趋势在1%的水平上具有显著性。研究区域内35岁以上女性的总出生比例同时下降。对319例索引病例中的175例（54.9%）进行了细胞遗传学分析。其中，161例为三体（92%），11例为易位（6.3%），3例为嵌合体（1.7%）。1969年至1979年期间，进行了4例因唐氏综合征而终止妊娠的手术，均为三体。计算了1960年至1964年、1965年至1969年、1970年至1974年以及1975年至1979年每五年的唐氏综合征年龄特异性发病率。在此期间没有统计学上的显著变化。有人认为唐氏综合征发病率的下降可以用母亲平均年龄的下降来解释。
