Supplementary Material for: Heterogeneity of Frailty Trajectories and Associated Factors in the Lothian Birth Cohort 1936

Introduction: Recent research suggests that the experience of frailty progression may be heterogeneous, with latent subpopulations of older adults following distinct trajectories of frailty. We aimed to investigate this notion and determine whether certain factors are associated with the membership of these subpopulations. Methods: Data from 5 data waves collected over 12 years in participants of the Lothian Birth Cohort 1936, aged 70 at baseline, were used to derive the frailty index (FI) (NW1 = 1,091, NW5 = 431). These were used in latent class mixed modelling to estimate subpopulations of frailty trajectories. Results: A quadratic latent class mixed model found 3 distinct groupings, which followed a low (61%, n = 632), medium (36%, n = 368), or high (3%, n = 28) FI trajectory. Each grouping had different intercepts and slopes, with the high grouping following the steepest trajectory indicating a rapid increase in frailty. Findings showed that in general, those in the low grouping were younger, had higher education, higher age 11 cognitive ability, and were from a higher social class than those in the medium and high groupings. Discussion/Conclusion: Our findings demonstrate heterogeneity in frailty trajectories over 12 years in individuals aged 70 years at baseline. Membership of higher frailty trajectory groupings was associated with lower social class, less education, and lower childhood cognitive ability, indicating the potential for future interventions to target individuals who are at the greatest risk of belonging to the high frailty trajectory. Future research is required to continue this line of inquiry by exploring other risk and protective factors, and importantly, to assess whether it is possible to realign an individual’s membership to a less detrimental grouping of frailty trajectory.

研究背景：近期研究表明，衰弱进展的过程存在异质性，老年人群的潜在亚群会遵循不同的衰弱轨迹。本研究旨在验证这一观点，并明确是否存在某些因素与这些亚群的归属相关。
研究方法：本研究使用了洛锡安出生队列1936（Lothian Birth Cohort 1936）参与者的12年间5轮随访数据，基线时参与者年龄为70岁，以此推导衰弱指数（frailty index, FI）（第1轮样本量NW1=1091，第5轮样本量NW5=431）。随后采用潜类别混合模型（latent class mixed modelling）对衰弱轨迹的亚群进行估计。
研究结果：二次潜类别混合模型识别出3个截然不同的分组，分别对应低（61%，n=632）、中（36%，n=368）和高（3%，n=28）衰弱指数轨迹组。各组的截距与斜率均存在差异，其中高轨迹组的增长斜率最陡，提示衰弱程度快速升高。进一步分析显示，总体而言，低轨迹组参与者相较于中、高轨迹组参与者更年轻、受教育程度更高、11岁时的认知能力更强，且社会阶层更高。
讨论与结论：本研究结果证实，基线年龄为70岁的老年人群在12年间的衰弱轨迹存在异质性。衰弱轨迹分组层级更高的参与者，其社会阶层更低、受教育程度更低、儿童时期认知能力更差，这表明未来可针对高衰弱轨迹风险人群开展干预。未来仍需进一步探索其他风险与保护因素，并重点评估是否可通过干预手段将个体的轨迹归属调整至危害性更低的分组，以延续该研究方向。