Older people who feel their life still has purpose are less likely to get memory loss, a survey has suggested.
More than 900 people were tracked for an average of 14 years in the US state of Illinois, to see whether they developed mild cognitive impairment (MCI) or dementia.
MCI is classed as the stage between an age-related decline in memory and thinking and a dementia diagnosis.
Factors taken into account when assessing a feeling of purpose included relating positively to others, personal growth, self-acceptance, autonomy and mastery of one's environment.
An international team of researchers found people who developed MCI showed a faster decline in psychological wellbeing than those who were "cognitively intact".
Those that developed MCI were found to lack a purpose in life three years before diagnosis.
In addition, they had lower levels of personal growth six years before diagnosis.
Some 29% of those taking part in the study were diagnosed with mild cognitive impairment.
Among that group, 34% were also diagnosed with dementia.
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The research team said: "Psychological wellbeing became significantly lower before MCI diagnosis.
"Reduced psychological wellbeing may serve as a predictor for impaired cognitive function.
"Post-diagnostic psychological support should be planned for people diagnosed with dementing disorders."
The paper is published in the Journal of Neurology, Neurosurgery and Psychiatry.