Effect of retirement on cognitive function: the Whitehall II cohort study

European Journal of Epidemiology, Dec 2017

According to the ‘use it or lose it’ hypothesis, a lack of mentally challenging activities might exacerbate the loss of cognitive function. On this basis, retirement has been suggested to increase the risk of cognitive decline, but evidence from studies with long follow-up is lacking. We tested this hypothesis in a cohort of 3433 civil servants who participated in the Whitehall II Study, including repeated measurements of cognitive functioning up to 14 years before and 14 years after retirement. Piecewise models, centred at the year of retirement, were used to compare trajectories of verbal memory, abstract reasoning, phonemic verbal fluency, and semantic verbal fluency before and after retirement. We found that all domains of cognition declined over time. Declines in verbal memory were 38% faster after retirement compared to before, after taking account of age-related decline. In analyses stratified by employment grade, higher employment grade was protective against verbal memory decline while people were still working, but this ‘protective effect’ was lost when individuals retired, resulting in a similar rate of decline post-retirement across employment grades. We did not find a significant impact of retirement on the other cognitive domains. In conclusion, these findings are consistent with the hypothesis that retirement accelerates the decline in verbal memory function. This study points to the benefits of cognitively stimulating activities associated with employment that could benefit older people’s memory.

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Effect of retirement on cognitive function: the Whitehall II cohort study

European Journal of Epidemiology Effect of retirement on cognitive function: the Whitehall II cohort study Baowen Xue 0 1 2 3 Dorina Cadar 0 1 2 3 Maria Fleischmann 0 1 2 3 Stephen Stansfeld 0 1 2 3 Ewan Carr 0 1 2 3 Mika Kivim a¨ki 0 1 2 3 Anne McMunn 0 1 2 3 Jenny Head 0 1 2 3 Retirement 0 1 2 3 0 Department of Behavioural Science and Health, Institute of Epidemiology and Health Care, School of Life and Medical Sciences, University College London , London , UK 1 Biostatistics and Health Informatics, Institute of Psychiatry, Psychology and Neuroscience, King's College London , London , UK 2 Research Department of Epidemiology and Public Health, Institute of Epidemiology and Health Care, School of Life and Medical Sciences, University College London , London , UK 3 Centre for Psychiatry, Wolfson Institute of Preventive Medicine, Barts and the London School of Medicine and Dentistry, Queen Mary University of London , London , UK reasoning, phonemic verbal fluency, and semantic verbal fluency before and after retirement. We found that all domains of cognition declined over time. Declines in verbal memory were 38% faster after retirement compared to before, after taking account of age-related decline. In analyses stratified by employment grade, higher employment grade was protective against verbal memory decline while people were still working, but this 'protective effect' was lost when individuals retired, resulting in a similar rate of decline post-retirement across employment grades. We did not find a significant impact of retirement on the other cognitive domains. In conclusion, these findings are consistent with the hypothesis that retirement accelerates the decline in verbal memory function. This study points to the benefits of cognitively stimulating activities associated with employment that could benefit older people's memory. Cognition; Longitudinal study; Piecewise regression; Employment grade Introduction Good cognitive functioning represents an essential element of healthy ageing and independent living [ 1 ]. There is some evidence that ageing affects cognitive functions that are primarily associated with executive processing and other functions of the frontal lobe [ 2, 3 ]. Thus, fluid abilities, such as memory, processing speed, and spatial ability tend to decline faster with age than crystallised functions, including vocabulary, information and comprehension [ 4–6 ]. However, the decline in these abilities is not necessarily homogenous across the population, as some people maintain cognitive vitality even into extreme old age [ 7–9 ]. On the one hand, there is evidence that the adult brain shows neuroplasticity and neurogenesis, representing the brain’s ability to generate new neurons and rewire itself [ 10–12 ]. On the other hand, accelerated deterioration or impairment in one or more cognitive functions beyond the ‘normal’ age-related decline could be predictive of the onset of dementia, a major cause of disability and dependency among older people worldwide [ 13, 14 ]. Therefore, it is important to identify and understand the predictors of interindividual differences in cognitive decline. The theory of cognitive reserve proposes that some individuals have a larger cognitive reserve than others. It has been postulated that innate cognitive resources (such as childhood IQ), cognitive stimulation during brain maturation in childhood (such as education), and cognitively engaged lifestyle during adulthood (such as cognitively demanding occupation) can increase cognitive reserve, thus building up a buffer against cognitive decline in old age [ 15, 16 ]. The ‘use it or lose it’ hypothesis similarly suggests that a person can maintain cognitive function by engaging in cognitively demanding activities, whereas failing to keep mentally active will detrimentally affect cognitive function and could accelerate cognitive decline or even the onset of dementia [17]. Accordingly, retirement may be a potential trigger for cognitive decline, assuming that retirees leave paid work that is cognitively demanding. Many studies have supported this assumption showing that retirement is associated with lower cognitive functioning [ 18–23 ], and later retirement is associated with better cognition and lower risk of dementia [ 24–27 ], although some studies have found no association [ 28, 29 ] or even a positive effect [30] of retirement on levels of cognition. When studying the effects of retirement on cognition, it is important to consider reverse causality. Declines in cognitive function may negatively affect the management of work tasks and thus could be a determinant of the decision to retire [ 31, 32 ]. For example, chronic diseases, such as stroke, might affect both cognitive function and retirement decisions [ 33, 34 ]. The vast majority of studies have compared retirees with working people to assess the potential effect of retirement on cognition, and it is possible that their r (...truncated)


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Baowen Xue, Dorina Cadar, Maria Fleischmann, Stephen Stansfeld, Ewan Carr, Mika Kivimäki, Anne McMunn, Jenny Head. Effect of retirement on cognitive function: the Whitehall II cohort study, European Journal of Epidemiology, 2017, pp. 1-13, DOI: 10.1007/s10654-017-0347-7