Do Cognitive and Physical Functions Age in Concert from Age 70 to 76? Evidence from the Lothian Birth Cohort 1936

Abstract

Abstract. The present study concerns the relation of mental and bodily characteristics to one another during ageing. The 'common cause' theory of ageing proposes that declines are shared across multiple, seemingly-disparate functions, including both physical and intellectual abilities. The concept of 'reserve' suggests that healthier cognitive (and perhaps bodily) functions from early in life are protective against the effects of senescence across multiple domains. In three waves of physical and cognitive testing data from the longitudinal Lothian Birth Cohort 1936 (n = 1,091 at age 70 years; n = 866 at 73; n = 697 at 76), we used multivariate growth curve modeling to test the 'common cause' and 'reserve' hypotheses. Support for both concepts was mixed: although levels of physical functions and cognitive functions were correlated with one another, physical functions did not decline together, and there was little evidence for shared declines in physical and mental functions. Early-life intelligence, a potential marker of system integrity, made a significant prediction of the levels, but not the slopes, of later life physical functions. These data suggest that common causes, which are likely present within cognitive functions, are not as far-reaching beyond the cognitive arena as has previously been suggested. They also imply that bodily reserve may be similar to cognitive reserve in that it affects the level, but not the slope, of ageing-related declines.

Cohort Profile Update: The Lothian Birth Cohorts of 1921 and 1936

“…In multivariate analyses, possession of the APOE e4 allele is one of the few robust independent predictors of relatively greater older-age cognitive decline 25 . There is some evidence that physical fitness may be protective against decline, 16 , 25 though physical and cognitive processes in general may be influenced by different ageing processes, because evidence for cognitive and physical functions declining in tandem is minimal 28 …”

Associations Between Aging-Related Changes in Grip Strength and Cognitive Function in Older Adults: A Systematic Review

“…Since this systematic review focused on changes in cognition and grip strength in relation to each other over time, studies reporting baseline effects on within person change were not reviewed. Six citations (1,4,10,(28)(29)(30) met full eligibility criteria. These studies were determined to be sufficiently methodologically rigorous (33).…”

“…Study and sample characteristics Six citations derived from four different longitudinal studies met the full systematic review inclusion criteria: Christensen and colleagues (4); Christensen and colleagues (30); Deary and colleagues (10); MacDonald and colleagues (28); Ritchie and colleagues (29); and Sternäng and colleagues (1). Table 1 provides more information on the demographic characteristics and measures of these studies.…”

“…The majority of participants were female in all studies, with a mean age spanning 65 in the Swedish Adoption/Twin Study of Aging [SATSA (1)] to 79 in the LBC1921 (10). Three reports were from two longitudinal studies based in Europe (1,10,29); two reports were from one longitudinal study in Australia (4,30), and one was from Canada (28). Average years of formal education were only reported in two studies: participants in the VLS had a mean of 15 years of education (28), while the CLS sample mean was 12 years (4).…”

“…Although there are some baseline versus baseline studies (15)(16)(17)(18), and quite a few baseline versus changes studies (8,(17)(18)(19)(20)(21)(22)(23)(24)(25)(26)(27), only a few studies have evaluated associations among rates of change (1,4,10,(28)(29)(30). Change versus change studies provide evidence of whether, and the extent to which, these components change together over time and the magnitude of this association.…”