Does age at onset have clinical significance in older adults with bipolar disorder?

While age at onset may be useful in explaining some of the heterogeneity of bipolar disorder (BD) in large, mixed age groups, investigations to date have found few meaningful clinical differences between early versus late age at onset in older adults with BD.Data were collected from sixty-one subjects aged 60 years and older, mean (SD) age 67.6 (7.0), with BD I (75%) and II (25%). Subjects were grouped by early (40 years; n = 43) versus late (≥ 40 years; n = 18) age at onset. Early versus late onset groups were compared on psychiatric comorbidity, medical burden, and percentage of days well during study participation.Except for family history of major psychiatric illnesses, there were no differences between the groups on demographic or clinical variables. Patients with early and late onset experienced similar percentages of days well; however, those with early onset had slightly more percentage of days depressed than those with late onset (22% versus 13%)Distinguishing older adults with BD by early or late age at onset has limited clinical usefulness.