Stolz Erwin, Schultz Anna, Hoogendijk Emiel O, Theou Olga, Rockwood Kenneth
Institute of Social Medicine and Epidemiology, Medical University of Graz, Graz, Austria.
Department of Epidemiology & Data Science, Amsterdam Public Health Research Institute, Amsterdam UMC-Location VU University Medical Center, Amsterdam, the Netherlands.
J Gerontol A Biol Sci Med Sci. 2024 Dec 11;80(1). doi: 10.1093/gerona/glae262.
Reversible short-term fluctuations in the frailty index (FI) are often thought of as representing only noise or error. Here, we assess (i) the size and source of short-term FI fluctuations, (ii) variation across sociodemographic characteristics, (iii) association with chronic diseases, (iv) correlation with age, frailty level, frailty change, and mortality, and (v) whether fluctuations reflect discrete health transitions.
Nationwide, biweekly longitudinal data from 426 community-dwelling older adults (70+) were collected in the FRequent health Assessment In Later life (FRAIL70+) study using a measurement burst design (5 122 repeated observations, median of 13 repeated observations per person). We calculated the intraindividual standard deviation of the FI and used location-scale mixed regression models.
Mean intraindividual standard deviation was 0.04 (standard deviation = .03). Fluctuations were driven foremost by cognitive problems, somatic symptoms, and limitations in instrumental and mobility-related activities of daily living. Short-term fluctuations correlated with higher FI levels (r = 0.62), 1-year FI change (r = 0.26), and older age (+3% per year). Older adults who took to bed due to a health problem (+50%), those who had an overnight hospital stay (+50%), and those who died during follow-up (+44%) exhibited more FI fluctuations.
Short-term FI fluctuations were neither small nor random. Instead, as older adults become frailer, their measured health also becomes more unstable; hence, short-term fluctuations in overall health status can be seen as a concomitant phenomenon of the aging process. Researchers and clinicians should be aware of the existence of reversible fluctuations in the FI over weeks and months and its consequences for frailty monitoring.
衰弱指数（FI）的可逆短期波动通常被认为仅代表噪声或误差。在此，我们评估（i）短期FI波动的大小和来源，（ii）社会人口学特征的差异，（iii）与慢性病的关联，（iv）与年龄、衰弱水平、衰弱变化和死亡率的相关性，以及（v）波动是否反映离散的健康转变。
在“晚年频繁健康评估（FRAIL70+）”研究中，采用测量突发设计（5122次重复观察，每人中位数为13次重复观察），收集了426名社区居住的70岁及以上老年人的全国性双周纵向数据。我们计算了FI的个体内标准差，并使用位置-尺度混合回归模型。
个体内平均标准差为0.04（标准差=0.03）。波动主要由认知问题、躯体症状以及工具性日常生活活动和与移动相关的日常生活活动受限所驱动。短期波动与较高的FI水平（r=0.62）、1年FI变化（r=0.26）和较高年龄（每年增加3%）相关。因健康问题卧床的老年人（增加50%）、住院过夜的老年人（增加50%）以及随访期间死亡的老年人（增加44%）表现出更多的FI波动。
短期FI波动既不小也不随机。相反，随着老年人变得更加衰弱，他们所测量的健康状况也变得更加不稳定；因此，总体健康状况的短期波动可被视为衰老过程的伴随现象。研究人员和临床医生应意识到FI在数周和数月内存在可逆波动及其对衰弱监测的影响。
