Massa Fernando, Marroig Alejandra, Rodgers Joe, Hoffer Scott M, Muniz-Terrera Graciela
Instituto de Estadística, Universidad de la República, Montevideo, Uruguay.
Department of Psychology and Human Development, Vanderbilt University, Nashville, Tennessee, USA.
Innov Aging. 2024 Sep 13;8(10):igae082. doi: 10.1093/geroni/igae082. eCollection 2024.
Cross-sectional studies have shown improvements in cognition in later-born cohorts. However, it remains unclear whether these cohort effects extend beyond cognitive levels and are also detectable in the rate of age-related cognitive decline. Additionally, evidence is scarce on the presence and consistency of cohort effects throughout different segments of the distribution of cognitive trajectories.
This study evaluates the existence and variability of cohort effects across the entire distribution of aging-related trajectories of verbal fluency. With this purpose, we develop sex and education-adjusted longitudinal norms of verbal fluency using data from 9 waves of the English Longitudinal Study of Aging (ELSA) by fitting quantile mixed models. The effect of age was modeled using splines to assess birth cohort effects, after grouping individuals in 5-year groups from 1920 to 1950 according to their age at study entry. To test for possible cohort effects across the 10th, 50th, and 90th quantiles, the coefficients associated with the splines were allowed to vary among cohorts.
Our results suggest that, consistently across longitudinal quantiles, decline in verbal fluency across age is less pronounced for later-born individuals ( < .001), supporting the hypothesis of cohort effects. Additionally, we also found that quantiles of verbal fluency at any age are shifted upwards in later-born cohorts compared to those in earlier-born cohorts.
These results enhance our understanding of cognitive decline in older adults by demonstrating that cohort effects on cognition are observable both cross-sectionally and longitudinally, affecting the entire range of verbal fluency trajectories.
横断面研究表明，后出生队列的认知能力有所改善。然而，这些队列效应是否超出认知水平，以及在与年龄相关的认知衰退率中是否也能检测到，仍不清楚。此外，关于认知轨迹分布的不同部分中队列效应的存在和一致性的证据很少。
本研究评估了在语言流畅性与衰老相关轨迹的整个分布中队列效应的存在和变异性。为此，我们通过拟合分位数混合模型，使用来自英国老年纵向研究（ELSA）9个波次的数据，制定了按性别和教育程度调整的语言流畅性纵向规范。在根据个体进入研究时的年龄将其分为1920年至1950年的5年组后，使用样条函数对年龄效应进行建模，以评估出生队列效应。为了检验在第10、50和90分位数上可能存在的队列效应，允许与样条函数相关的系数在不同队列之间变化。
我们的结果表明，在纵向分位数上一致地，后出生个体在整个年龄范围内语言流畅性的下降不太明显（<0.001），支持了队列效应的假设。此外，我们还发现，与早出生队列相比，后出生队列中任何年龄的语言流畅性分位数都向上偏移。
这些结果通过证明队列效应在横断面和纵向上对认知的影响都是可观察到的，且影响了语言流畅性轨迹的整个范围，增强了我们对老年人认知衰退的理解。
