Bipolar disorder in Sardinian population: Age at onset as an endophenotype?

BIPOLAR DISORDER IN SARDINIAN POPULATION:AGE AT ONSET AS AN ENDOPHENOTYPE? The discovery of the genetic factors implicated in the predisposition to Bipolar Disorder (BD) may greatly profit from genetic studies in isolated populations, as Sardinian population, with lesser genetic heterogeneity and probably fewer environmental differences than outbred populations. The identification of endophenotypes, such as a subgroup with early age at onset, may facilitate the finding of genes involved in the etiology of BD. Assesing the presence of an early onset group of bipolar subjects in a Sardinian population of at least four generations of Sardinian ancestry with the objective to design a linkage study with candidate genes. 300 probands were recruited using the FH-RDC. Pypsi, a software planned for the recording of clinical data, enabled as the management of the acquired informations. Age of onset was defined as the first reliably diagnosed hypo-/manic or depressive episode. Admixture analysis was used to decompose the age-at –onset distribution into a mixture of theoretical normal distributions. Weclinically characterized all probands by sex, diagnosis (BPI, BPII, SAM), age-at-onset and suicide attempts. Referring to 180 BPI probands the age-at-onset consisted of a mixture of four normal distributions with means of 18.13 (SD¼0.56), 25.06 (SD¼3.36), 42.13 (SD¼4.80) and 59.94 (SD¼2.05) with a p-value¼0.0106. Cutoff points at ages 19 and 37 were derived from this analysis and used to define ageat- onset subgroups