Objective: Cognitive impairment may interfere with psychosocial functioning in bipolar disorder (BD). There is limited information regarding the cognitive function of elderly bipolar patients with onset at a young age. The present study aimed to investigate the frequency and the determinants of cognitive impairment in elderly early-onset bipolar patients. Methods: Using the Clock-drawing Test (CDT), the Mini Mental State Examination (MMSE), and the Cognitive Abilities Screening Instrument (CASI), we examined euthymic patients with bipolar I disorder in Taiwan, aged 60 years and older. Clinical data were obtained by reviewing medical records and personal interviews with patients and their family members. The onset of BD prior to the age of 40 years is defined as 'early-onset'. Results: Of the 52 early-onset patients, 42.3% were determined to have cognitive impairment by exhibiting either abnormal CDT or education-adjusted MMSE scores. In a multiple regression model, years of education and the age at the last manic/hypomanic (but not depressive) episode accounted for the greatest variance in both MMSE and CASI scores. While educational level and the age at the last manic/hypomanic episode were not considered in the regression model, onset with depressive syndrome and current age explained 21.5% of the variance in MMSE scores. Age at the first depressive episode, the first manic episode before the age of 40 years, and comorbid diabetes accounted for 16.7% of the variance in CASI scores. Conclusion: There appeared to be a sizable proportion of elderly early-onset bipolar patients having cognitive impairment. It is suggested that clinical manifestation of first-onset affective episode and impact of medical comorbidity affect the cognition of early-onset BD in later life.
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