[A fixed cohort study of disability trajectory of the dying elderly in China].

Objective: To explore the trajectory of disability in the dying elderly in China. Methods: Based on the activity of daily living (ADL) data from the 2002-2018 Chinese Longitudinal Healthy Longevity Survey, the longitudinal item response theory (LIRT) model was fitted with the difficulty threshold parameters to analyze the ADL loss in the elderly in China. Then, a mixed-effects model was fitted to analyze the trajectory of the disability level of the dying elderly. Results: A total of 5 817 old adults who entered the cohort in 2002 were included, in whom 41.81% were males, with a baseline age of (86.80±12.40) years and a follow-up time of 4 (3,8) years. The results of LIRT showed that the lowest difficulty threshold parameter in the basic activity of daily living (BADL) was partially disability on bathing (0.41±0.05), and the highest was entirely disability on indoor movement (6.19±0.16). In comparison, the lowest difficulty threshold parameter in instrumental activity of daily living (IADL) was partially disability on using public transportation (-3.01±0.07), and the highest was entirely disability on visiting neighbors (1.51±0.07). In the trajectory of disability, the average dependency in ADL was lower in dying men than in dying women (P<0.001), in the elderly living alone than in the elderly living with family members (P<0.001) and in the non-illiterate elderly than in the illiterate elderly (P<0.001). The estimated value of both the linear change rate and quadratic coefficient of disability level development with time were 0.231 (P<0.001) and 0.002 (P<0.001). Conclusions: In China, the development of disability in the elderly in China has its characteristics, IADL disability might occurs earlier than BADL. Among the IADL/BADL items, the disability of lower limb-based items is more prone to occur compared with upper limb-based items, and the disability of complex items is more prone to occur compared with simple items, and the growth rate of the disability trajectory also accelerates over time. It is necessary to pay attention to old women, old people living with family members, old people with low education level and old people with poor cognitive function in the disability prevention.目的： 探索我国老年人临终前的失能发展轨迹。 方法： 利用2002-2018年中国老年人健康长寿影响因素调查中的日常生活活动能力（ADL）数据拟合纵向项目反应理论（LIRT）模型，通过其中的难度阈值参数分析我国老年人ADL失能顺序；进而拟合混合效应模型分析老年人临终前失能水平的变化轨迹。 结果： 共纳入2002年进入队列的5 817名老年人，其中男性占41.81%，基线年龄为（86.80±12.40）岁，随访时间M（Q1，Q3）为4（3，8）年。LIRT分析结果显示，基本日常生活活动能力（BADL）中难度阈值参数最低的是洗澡部分受限（0.41±0.05）、最高的是室内移动完全受限（6.19±0.16）；而工具性日常生活活动能力（IADL）中难度阈值参数最低的是乘坐公共交通工具部分受限（-3.01±0.07），最高的是探访邻居完全受限（1.51±0.07）。失能发展轨迹中，临终前男性较女性平均失能水平更低（P<0.001），独居老人较非独居老人失能水平更低（P<0.001）；文盲老人失能水平高于非文盲老人（P<0.001）。失能水平随时间的线性变化率与二次项系数的估计值分别为0.231（P<0.001）与0.002（P<0.001）。 结论： 我国老年人失能过程存在一定的规律性，IADL失能早于BADL，失能项目中下肢为主的项目比上肢为主的项目易失能，复杂项目比简单项目易失能。失能轨迹的增速会随时间加快，对失能人群的干预重点应放在女性、非独居、文盲老年人上。.