Can we spot deleterious ageing in two waves of data? The Lothian Birth Cohort 1936 from ages 70 to 73

Wendy Johnson ,Alan J Gow ,Janie Corley ,Paul Redmond ,Ross Henderson ,Catherine Murray ,John M Starr ,Ian J Deary

doi:10.14301/llcs.v3i3.198

Abstract

‘Younger’ old age (the late 60s through early 70s) is, for many, a period of stability of lifestyle and considerable freedom to pursue leisure activities. Despite the stability that many enjoy, the mortality rate is about 2% per year in western nations. This increases to about 5% by age 80. It would be useful to know if those most vulnerable can be identified through patterns of deleterious ageing, and especially if this could be accomplished with just two waves of data. The Lothian Birth Cohort 1936 was surveyed on a host of individual difference variables including cognition, personality, biomarkers of physical health, and activities at ages 70 and 73 years. Overall, the group showed the expected basic stability in mean levels for these variables, but some individuals had died and others did show substantial changes that could be considered statistically reliable. These presumably reliable changes were at least as likely to be positive (reflecting improved condition/ability) as negative (reflecting decline/ageing). Moreover, limitations in the estimated reliabilities of the measures meant that most of the observed changes could not be considered reliable. The changes clustered only weakly around general health to predict death over the next approximately two years. We concluded that two waves of longitudinal data were not sufficient to assess meaningful patterns of ageing, despite often being used to do so.

Highlights

‘Younger’ old age is, for many in developed economies, a period of stability of lifestyle and general condition
Even samples screened for clinical manifestations of impairment would inevitably include some who had entered this period but remained undiagnosed, and their numbers could be expected to increase with age, which could create the declines in mean function with age that studies consistently show
The purpose of this study was to explore the potential capacity to use two data waves to identify individuals who, in the period from ages 70 to 73 years, might be experiencing negative changes in many areas consistent with terminal decline. We did this through examination of three questions: 1) How and to what extent did individuals change during this period? 2) Were there correlates or predictors of these changes? and 3) Did changes tend to cluster in ways that could distinguish healthy ageing from terminal decline? Our analysis made use of the Lothian Birth Cohort 1936 (LBC1936; Deary et al, 2007; Deary et al, in press), a sample of 1,091 initially healthy 70-year-olds living in the Edinburgh area of Scotland, all of whom were born in 1936 and who completed a broad assessment of both cognitive and physical function

Summary

Introduction

‘Younger’ old age (the late 60s through early 70s) is, for many in developed economies, a period of stability of lifestyle and general condition. As longitudinal data samples have proliferated and statistical analytical techniques have improved, research efforts have been directed toward describing individual trajectories of decline (e.g., Finkel et al, 2005; McGue & Christensen, 2002) and/or the specific interval before death at which some period of ‘terminal decline’ begins (e.g., Rabbitt et al, 2011; Sliwinski et al, 2006; Terrera et al, 2011; Wilson et al, 2003) These studies have produced widely varying results about the extent of change, its rate of acceleration if considered, and the length of any terminal decline interval.

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