Objective To explore the characteristics of cognitive impairments in euthymic patients with early-on⁃set or late-onset bipolar I disorder (BD-I). Methods Ninety-four with onset age less than 21 (early onset group), 41 eu⁃thymic patients with onset age above 35 (late onset group) and 135 normal controls with matched education and age were enrolled. Seven classical neuropsychological tests were used to assess attention, processing speed, working memory and executive functions. Results The early-onset group was significantly worse than its corresponding normal controls in 14 indexes of all tests, including digital symbol, digital span, visual graphic reproduction (c1 and c2), time of TMT-A and TMT-B, verbal fluency, number of sorting, error and preserved error in WCST, as well as total score, completed missions, planning time and executing time in TOH (P<0.05). Moreover the effect size of difference were more than 0.4 in verbal fluency, time of TMT-A and TMT-B, and executing time in TOH. Compared with its matched control group, the late-on⁃set group was significantly impaired in 9 indexes, including digital span, visual graphic reproduction (c1,c2 and total), time of TMT-A, number of error and preserved error in WCST, as well as total score and completed missions in TOH (P<0.05), merely two indexes of TOH with effect size more than 0.4, while the late-onset group was no significantly impaired in digital symbol, TMT-B and verbal fluency. Conclusions There are significant cognitive impairments in euthymic BD-I patients with no matter early-onset or late-onset. But it seems that the cognitive impairments in early-onset bipo⁃lar disorder are more extensive and serious.%目的：研究早发和晚发的双相障碍I型患者稳定期认知功能损害特点。方法纳入首次发病年龄≤21岁（早发组94例）和≥35岁（晚发组41例）的稳定期双相障碍I型患者，以及分别与两组患者年龄、性别、受教育程度相匹配的正常对照135名（分别设为对照组1共94名和对照组2共41名），均予以7个经典的神经心理测试，评估注意力/处理速度、工作记忆和执行功能等。结果早发组在数字符号、连线测验（trail making test， TMT）A时间、TMT-B时间、数字广度顺背、视觉图形再生c1和c2、言语流畅性、威斯康星卡片测验（Wisconsin card sorting test-modified，WCST）分类数、总错误数和持续错误数以及汉诺塔测验（tower of Hanoi，TOH）总分、完成任务数、计划时间和执行时间共14个指标的成绩较对照组1差（均P<0.05），其中言语流畅性、TMT-A时间、TMT-B时间和TOH执行时间的差异效应量均大于0.4；与对照组2比较，晚发组的TMT-A时间、数字广度顺背、视觉图形再生c1、c2和总分、WCST总错误数、持续错误数以及TOH总分、完成任务数共9个指标成绩较差（均P<0.05），仅TOH两个指标的效应量大于0.4。结论早发和晚发双相障碍I型患者稳定期仍存在多个维度的认知损害，前者的损害可能更广泛、更严重。
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