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.

引言：近期研究表明，衰弱进展的表现存在异质性，老年人群的潜在亚群遵循各不相同的衰弱轨迹。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联。
方法：本研究使用了洛锡安1936年出生队列（Lothian Birth Cohort 1936）参与者的12年间5次随访数据，该队列参与者基线时年龄为70岁，其中基线（NW1）有效样本量为1091例，第5次随访（NW5）有效样本量为431例，以此构建衰弱指数（frailty index, FI）。随后采用潜类别混合模型对衰弱轨迹的潜在亚群进行估算。
结果：二次项潜类别混合模型识别出3个不同组别，分别遵循低（61%，n=632）、中（36%，n=368）或高（3%，n=28）衰弱指数轨迹。各组的截距与斜率均存在显著差异，其中高衰弱轨迹组的斜率最陡，提示其衰弱程度呈快速升高趋势。研究发现，与中、高衰弱轨迹组参与者相比，低衰弱轨迹组参与者整体更年轻、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。归属更高衰弱轨迹组的参与者，其社会阶层更低、受教育程度更低、童年期认知能力更差，这提示未来可针对最有可能归属高衰弱轨迹组的人群开展干预。未来仍需进一步开展相关研究，探索其他风险与保护因素，尤为重要的是，需评估是否可通过干预手段使个体的轨迹归属向危害更小的衰弱轨迹组别转变。