Population prevalence of Down's syndrome in the United Kingdom.

Background: Aim was to estimate the age and sex-stratified prevalence of Down's syndrome (DS) in the United Kingdom (UK) general population using a large primary care database.

Method: Data source was the Clinical Practice Research Datalink. We divided the number of individuals with a record of DS present on 01/07/2014 by the total number of individuals, and computed Wilson's confidence intervals. Prevalence by age and sex was represented using local linear smoothing plots.

Results: On July 1(st) 2014, 1159 females and 1317 males with DS were present in the data, corresponding to a prevalence of 5.9 per 10 000 (95% CI: 5.5; 6.2) in females and 6.8 (6.5; 7.2) per 10 000 in males. Prevalence of DS was increased in individuals aged 40 to 55 years compared to adjacent age groups.

Conclusions: A relative peak prevalence of DS at age 40-55 years may be attributed to the combined effects of a rise in life expectancy and the still limited availability of selective abortion.