MedWire News: Bipolar disorder (BD) patients can be divided into three groups based on age-at-onset (AAO) distributions, with patients in the earliest AAO group at greatest risk for suicide attempts, research shows.
In BD, "the ability to identify clinical variables capable of explaining some of the disease heterogeneity could improve the identification of the underlying pathophysiological bases of the disease," explain Federica Tozzi (GlaxoSmithKline R&D, Verona, Italy) and team.
They add: "As for other neuropsychiatric diseases, AAO has been proposed as a promising criterion by which to select more homogeneous subgroups of BD patients."
To investigate further, the team studied data on 964 patients with BD, aged an average of 47.2 years (range 18-84 years), recruited from three hospitals in Canada and the UK.
Data on clinical variables and AAO were collected from interviews with the patients using the Schedules for Clinical Assessment in Neuropsychiatry.
The researchers found that the mean AAO was 21.4 years, with AAO showing a peak frequency between the ages of 15 and 17 years, and a steady decrease after 21 years.
Admixture analysis revealed three distinct distributions of AAO, with age means of 16.1, 25.4, and 32.2 years, representing 64%, 6%, and 30% of the patients, respectively.
Further analysis showed that patients in the earliest onset group were 2.54 times more likely to have had depression at onset, 1.78 times more likely to have bipolar I disorder rather than bipolar II disorder, and 1.47 times more likely to have attempted suicide than those in the later-onset groups.
The risk for suicide attempts decreased with increasing AAO and was not affected by duration of illness, the researchers note in the journal Psychiatry Research.
Tozzi and team conclude: "Our results indicate that the AAO distribution in BD patients can be subdivided by admixture analysis into three normal distributions."
They add: "The evidence of AAO subgroups characterized by distinct clinical traits has implications for future research, suggesting AAO as a variable to consider in the investigation of biological and environmental risk factors for BD."
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