Age at Onset in Sardinian Bipolar I Patients: Evidence for Three Subgroups

Admixture analysis was applied in order to identify a model of separate normal distribution of age-at-onset characterized by different means, variances, & population proportions to allow for evaluation of different subgroups in a sample of 181 unrelated patients of Sardinian origin with bipolar disorder I. A Mann-Whitney test revealed a difference between the mean age-at-onset of subjects with a positive history of suicide & that of subjects with no such history. Multivariate logistic regression analysis showed that risk of suicide attempts was not influenced by years of illness. The regression model suggested an effect of age-at-onset, indicating that the risk of suicide attempts decreased with increasing age-at-onset. (14 refs.)