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Age at onset in Sardinian bipolar I patients: evidence for three subgroups
Author(s) -
Manchia Mirko,
Lampus Simona,
Chillotti Caterina,
Sardu Claudia,
Ardau Raffaella,
Severino Giovanni,
Zompo Maria Del
Publication year - 2008
Publication title -
bipolar disorders
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 2.285
H-Index - 129
eISSN - 1399-5618
pISSN - 1398-5647
DOI - 10.1111/j.1399-5618.2007.00572.x
Subject(s) - mann–whitney u test , population , bipolar disorder , homogeneous , medicine , demography , psychology , psychiatry , mood , combinatorics , mathematics , sociology
Objective: We studied age at onset (AAO) in order to assess the presence of different subgroups in a homogeneous genetic population, such as the Sardinian population. Methods: Admixture analysis was applied in order to identify a model of separate normal distribution of AAO characterized by different means, variances and population proportions to allow for evaluation of different subgroups in a sample of 181 unrelated patients of Sardinian origin with bipolar disorder (BP) type I. The Mann–Whitney test was used to compare the means of AAO between subjects with a history of suicide attempts and subjects with no such history. Results: The best‐fitting model had three components with means (SD) of 18.1 (2.3), 24.3 (5.3) and 41 (11.5) years, comprising 36%, 39% and 25% of the sample, respectively. We obtained two cut‐off points at 21 and 33 years, enabling the sample to be divided into three subgroups. The Mann–Whitney test revealed a difference between the mean AAO of subjects with a positive history of suicide attempts and that of subjects with no such history (p = 0.041). Conclusions: We found three AAO sub‐groups in our sample of BP I patients of Sardinian origin. Our findings add further support to the hypothesis whereby AAO acts as a clinical marker of biological heterogeneity in BP.