Subclinical memory impairment in unaffected siblings of patients with dementia

Objective: Family history of dementia is a known risk factor for dementia. The cognitive performance of unaffected siblings of dementia patients has been poorly studied. We aimed to determine whether clinically unaffected siblings of dementia patients have significant cognitive impairment compared to individuals who do not have first-degree relatives with dementia. Methods: We compared the cognitive performance of 67 patients with dementia (24 males; mean age 69.5), 90 healthy siblings of those patients (34 males; mean age 61.56) and 92 healthy adults (35 males; mean age 60.96) who have no first-degree relatives with dementia. We assessed learning and memory (Rey Auditory Verbal Learning Test (RAVLT)), short-term/working memory (Digit Span) executive functions (Stroop Test) and general intelligence (Raven Progressive Matrices). Test scores were compared among three groups, with regression-based adjustments for age, sex, and education. Results: As expected, the patients with dementia were impaired in all cognitive domains. In the Sibling Group, RAVLT total learning was significantly lower compared to controls (B = −3.192, p = .005). In a subgroup analysis, compared to controls, RAVLT delayed recall was poorer in the siblings of patients with early-onset (Conclusion: Clinically unaffected siblings of dementia patients seem to have a selective subclinical impairment in memory encoding. This impairment seems to be more prominent in siblings of patients with early-onset dementia who also have deficits in delayed recall. Future studies are needed to determine if the observed cognitive impairment deteriorates to dementia.

研究目的：痴呆家族史是公认的痴呆发病风险因素。目前针对痴呆患者临床未受累同胞的认知表现的相关研究仍相对匮乏。本研究旨在探究，与无一级亲属罹患痴呆的健康人群相比，痴呆患者临床未受累的同胞是否存在显著认知功能损害。
研究方法：本研究纳入67例痴呆患者（男性24例，平均年龄69.5岁）、90例上述患者的健康同胞（男性34例，平均年龄61.56岁）以及92名无一级亲属罹患痴呆的健康成年人（男性35例，平均年龄60.96岁），对三组人群的认知表现进行比较。本研究采用以下认知评估工具：学习记忆能力采用雷伊听觉言语学习测验（Rey Auditory Verbal Learning Test, RAVLT），短时/工作记忆采用数字广度测验（Digit Span），执行功能采用斯特鲁普测验（Stroop Test），一般智力采用瑞文渐进矩阵测验（Raven Progressive Matrices）。对三组的测验得分进行组间比较，并针对年龄、性别与受教育程度进行基于回归分析的校正。
研究结果：如预期所料，痴呆患者在所有认知领域均表现出功能损害。同胞组的RAVLT总学习得分显著低于对照组（B=-3.192，p=0.005）。亚组分析结果显示，与对照组相比，早发性痴呆患者同胞的RAVLT延迟回忆得分更低。
研究结论：痴呆患者临床未受累的同胞似乎存在记忆编码方面的选择性亚临床认知损害。该损害在早发性痴呆患者的同胞中更为显著，此类人群同时还存在延迟回忆能力缺陷。未来仍需开展进一步研究，以明确所观察到的认知损害是否会进展为痴呆。