ADP-induced platelet aggregation as a function of age in healthy humans.

In 120 healthy humans (58 males and 62 females) possible differences in platelet aggregability were investigated with respect to age and sex. By using a narrow range of final ADP concentrations (0.2-1.0 microM) primary and secondary aggregation were evaluated. The rate of primary aggregation was shown to be significantly related to increasing age and this was true for both sexes. As regards secondary aggregation the same pattern was seen in the group of male subjects. Thus, among the youngest (less than 34 years) the frequency of secondary waves was only one third of that encountered among the oldest (greater than 50 years). No similar association was detectable among the female subjects. The present study calls attention to some important issues which should be considered in platelet aggregation studies; the interpretation of data obtained from such studies invariably requires a careful selection of appropriate age- as well as sex-matched control groups.