Retirement Age and the Age of Onset of Alzheimer’s Disease: Results from the ICTUS Study

Abstract

ObjectivesTo test whether deferred retirement is associated with delayed onset of Alzheimer’s disease (AD), and, if so, to determine whether retirement age still predicts the age at onset of AD when two potential biases are considered.MethodsThe study sample was gathered from the Impact of Cholinergic Treatment Use/Data Sharing Alzheimer cohort (ICTUS/DSA), a European study of 1,380 AD patients. Information regarding retirement age, onset of symptoms and covariates was collected at baseline whereas age at diagnosis was gathered from the patient’s medical record prior to study entry. Linear mixed models, adjusted for gender, education, occupation, center, country, household income, depression and cardiovascular risk factors were conducted on 815 patients.Results(1) The global analyses (n = 815) revealed that later age at retirement was associated with later age at diagnosis (β = 0.31, p < 0.0001); (2) once the selection bias was considered (n = 637), results showed that this association was weaker but remained significant (β = 0.15, p = 0.004); (3) once the bias of the reverse causality (i.e., the possibility that subjects may have left the workforce due to prior cognitive impairment) was considered (n = 447), the effect was no longer significant (β = 0.06, p = 0.18).ConclusionThe present study supports that there is an association between retirement age and age at onset of AD. However, the strength of this association appears to be overestimated due to the selection bias. Moreover, the causality issue remains unresolved. Further prospective investigations are mandatory in order to correctly address this question.

A nationwide Swedish study of age at retirement and dementia risk

“…According to the literature, a later age of retirement is related to decreased dementia risk, including later onset of AD, 5‐8 and better preserved cognitive function 20 . The results from the present study, showing that a higher age of retirement is associated with a reduced risk of dementia, are consistent with these earlier findings.…”

“…A common explanation for why delaying retirement may be beneficial for cognitive health is that retirement may be associated with a drop in mental and social stimulation. Accordingly, it has been proposed that people who work for a longer time keep up their cognitive level for a longer period, thereby reducing the risk of dementia diseases or delaying its onset 5‐8 . As such, the results are consistent with a “use it or lose it” perspective and the cognitive reserve hypothesis 2,21 …”

“…For example, Lupton et al 5 conducted a retrospective study, based on probable AD cases, showing later retirement age to delay the onset of AD. Another retrospective study by Grotz et al 6 on AD patients that were referred to clinical centers for evaluation, indicated similar results in initial analyses. However, after considering potential bias due to reverse causality (ie, that persons may retire because of cognitive impairment) the effect of retirement on dementia risk was no longer significant 6 .…”

“…Another retrospective study by Grotz et al 6 on AD patients that were referred to clinical centers for evaluation, indicated similar results in initial analyses. However, after considering potential bias due to reverse causality (ie, that persons may retire because of cognitive impairment) the effect of retirement on dementia risk was no longer significant 6 . Furthermore, a large‐scale register based study, 8 involving self‐employed workers in France, revealed a hazard ratio for dementia risk of 0.97 (95% confidence interval [CI]) per extra year of age at retirement.…”

“…The potential protective effect of staying active longer for dementia is of fundamental importance also from a socioeconomic perspective. We may need to work longer to cope with increased costs associated with population aging seen in Western countries, and this issue have consequently been addressed in a few previous studies 5‐8 . For example, Lupton et al 5 conducted a retrospective study, based on probable AD cases, showing later retirement age to delay the onset of AD.…”