Low intrinsic capacity is associated with risk of developing mild cognitive impairment in the English Longitudinal Study of Ageing (ELSA)

Intrinsic capacity (IC) is a composite that includes five different domains related to a person's capacities: sensory, locomotion, vitality, psychological and cognitive. IC represents part of a global effort to promote healthy ageing, one aspect of which is healthy cognitive functioning. This study aimed to elucidate the association of IC and cognitive decline in older adults. Using data from the English Longitudinal Study of Ageing (ELSA, wave 6), IC composite was derived through z-score and item-response theory (IRT) methods in a sample of cognitively normal older adults (n = 731, aged 70.1 ± 6.77 years). Global cognition (GC) was derived by categorizing Mini-mental State Examination scores obtained in the same population 4-5 years later (ELSA-HCAP, 2018). After algorithm selection, GC categories were regressed on IC scores, demographic and lifestyle covariates. The IRT algorithm showed better model fit and strong associations with age, sex and education. Lower IC was associated with higher likelihood of developing mild cognitive impairment (MCI) 4 to 5 years after IC assessment. Increased age and lower education were also strong predictors of GC, whereas no significant effects were found for sex, physical activity, or number of comorbidities in the fully adjusted model. Although bivariate regressions showed that reduced moderate or vigorous physical activity and increased number of comorbidities are associated with higher odds of developing later MCI, the lack of associations between these covariates and GC in the fully adjusted model suggests a possible mediation effect on IC. No study had previously explored the association of IC on later cognitive impairment. Results agree with previous evidence associating low IC to females, older ages and lower education. Further research to reveal possible underlying mechanisms explaining this association is needed to improve our understanding and relevance of IC for healthy ageing.