Decline in psychological wellbeing may signal early mild cognitive impairment

Feeling that your life lacks purpose and that there are few opportunities for personal growth in older age may precede the development of mild cognitive impairment (MCI), a frequent precursor of dementia, suggests research published online in the Journal of Neurology Neurosurgery & Psychiatry.

These aspects of psychological wellbeing noticeably decline 2 to 6 years before MCI is diagnosed, even in the absence of evident signs, and irrespective of whether those affected go on to develop dementia, the findings indicate.

Mounting evidence links psychological wellbeing to brain aging, including the development of dementia. But much of the published research focuses on a sense of purpose, excluding the other aspects of wellbeing, explain the researchers.

These include self-acceptance, autonomy, feeling capable of managing one's immediate environment, having meaningful connections with others, and personal growth.

To strengthen the evidence base, the researchers explored changes over time in psychological wellbeing before and after diagnoses of MCI and dementia among 910 cognitively intact older adults (average age 79) participating in the Rush Memory and Aging Project.

This Project is an ongoing long term study that began in 1997. It includes older adults from senior and subsidised housing, continuous care retirement communities, social service agencies, church groups, and individual homes in northeastern Illinois, USA.

Study participants have annual check-ups that include neurological examinations, cognitive tests, medical history, and assessment of psychological wellbeing, which from 2008 onwards included all 6 components.

During an average monitoring period of 14 years, 265 (29%) developed MCI, 89 (34%) of whom went on to develop dementia. The final analysis is based on 229 participants with complete before and after data, including 73 who developed dementia.

Compared with participants who remained cognitively intact, those who developed MCI were more likely to be older, weigh less, and have lower levels of depressive symptoms and psychological wellbeing. 

Similarly, compared with those who didn't develop dementia, those who did were more likely to be older, female, to carry the gene linked to dementia (APOE ε4), and to have a lower level of psychological wellbeing.

After accounting for potentially influential factors, such as age, vascular disease and its risk factors, lifestyle, social activities and feelings of loneliness, those who developed MCI experienced a faster decline in psychological wellbeing, leading to a lower level of it 2 years before diagnosis, than those who remained cognitively intact. 

In particular, these people had lower levels of purpose in life and personal growth, beginning 3 and 6 years, respectively, before their diagnosis. 

The speed of psychological wellbeing decline was similar before and after their diagnosis for each component except for meaningful connections with others, which declined faster afterwards.

Wellbeing trajectories were similar for all participants with MCI regardless of whether they subsequently developed dementia, prompting the researchers to suggest that their findings "indicate that reduced psychological wellbeing even without apparent cognitive impairment may be a predictor of subsequent dementing disorders."

This is an observational study, and as such, no firm conclusions can be drawn about cause and effect. The study participants were well educated, which may introduce selection bias because of the 'healthy volunteer' effect, and most of them were White and female, which may limit the generalisability of the findings, acknowledge the researchers.

And the mechanisms underlying the association between wellbeing and cognitive function aren't well understood, they add. 

The two might be bi-directional: in other words, poorer cognition might influence psychological wellbeing as well as the other way round; greater wellbeing and better cognitive function may also share certain protective factors, they suggest.

And the discrepancies across the various wellbeing components may lie in differences in the level of cognitive processing required, they say. 

"Our findings indicate that personal growth and purpose in life may be more cognitively demanding than other components of wellbeing, and therefore may serve as more sensitive indicators of cognitive ageing," they write.

"Moreover, we found that positive relations with others declined rapidly after MCI diagnosis. People with impaired cognitive function may be less likely to engage in social and leisure activities than they were previously, which can cause further deterioration in their relationships with friends or others," they add. 

Psychological support should be planned for people diagnosed with dementing disorders, they advocate.