Elite swimmers and the D allele of the ACE I/D polymorphism

A polymorphism of the human angiotensin-1-converting enzyme (ACE) gene has been identified in which the presence (insertion, I allele) of a 287-bp fra gment rather than the absence (deletion, D allele) is associated with lower ACE activity. Several recent studies have shown an association of the I al lele with endurance performance, it being found with excess frequency in el ite distance runners, rowers and mountaineers. Other workers using heteroge neous cohorts of athletes from mixed sporting disciplines have found no suc h association. An increasing linear trend of I allele frequency with the di stance run amongst Olympic runners and an excess of the D allele amongst sp rinters led us to examine whether the ratio of I and D alleles in swimmers competing over different distances would also vary. Swimmers (n=120) from t he European and Commonwealth championships and an American college team had their ACE genotype determined and their gene and allele frequencies compar ed with several control groups, the most closely age-matched of which were 1248 military recruits. Of the 103 Caucasians, there was a significant exce ss of the D allele compared with this control group only in the truly elite swimmers of the European and Commonwealth championships (P=0.004). This as sociation remained in those competing over shorter distances (P=0.005 for 4 00 m and below) but not in the longer events. These findings were confirmed in three further large control groups. A population association study test ing whether a genetic marker (the ACE I/D polymorphism) occurs more frequen tly in cases (elite athletes) than in controls therefore requires a homogen eous cohort of subjects from the same sporting discipline.