medwireNews: A large study of patients with bipolar I disorder supports the concept that they can be divided into three subgroups based on their age at onset.
Jean-Michel Azorin (Sainte Marguerite Hospital, Marseilles, France) and co-workers used admixture analysis to categorize 1082 French patients based on their sociodemographic and clinical characteristics. Such an analysis avoids classifying patients according to arbitrary age-at-onset thresholds, they explain. Previous studies using the technique identified three subgroups of patients with age-at-onset cutoffs of about 20 and 30 years.
"Our findings are in accord with the results of these studies, suggesting that such a model may be highly robust," Azorin et al write in the Journal of Affective Disorders.
The patients were divided fairly evenly across the subgroups, with 28.3%, 38.5%, and 33.2% falling into the early-onset (≤20 years at onset), intermediate-onset (21-30 years), and late-onset (>30 years) groups. And there were clear patient and disease differences between the groups, particularly the early- and late-onset groups.
The early-onset group contained more men than the intermediate- and late-onset groups, at 45.8% versus 40.9% and 37.3%, respectively. Early-onset patients tended to have high scores on the Mania State Rating Scale, unstable mood, psychotic features and high scores for positive symptoms. In the course of disease, early-onset patients were the most likely to have rapid cycling, the least likely to have free intervals between mood episodes, and were the most likely to have attempted suicide. They also had the highest rates of substance abuse.
By contrast, patients in the late-onset group were more often female and had predominantly depressive symptoms. They had the highest rates of medical comorbidities and of alcohol abuse.
Of the three groups, the early-onset group had the longest delays to diagnosis and treatment, and these patients were often initially diagnosed with psychotic illnesses.
"The intermediate-onset subgroup displays a less contrasted picture, with a profile which seems to be a bit more balanced, as it may share features pertaining to both other subgroups," say the researchers.
They believe that the specific patient profiles identified via age at onset should "be considered in future research assessing efficacy of pharmacotherapy or psychotherapy as well as that aiming at the identification of specific biomarkers."
And the team stresses: "Delays longer than five years were found before correct diagnosis and treatment for each subgroup, suggesting that better knowledge of such patient profiles may help shortening these delays."
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