Having a Purpose in Life and the Risk of Cognitive Decline

There’s a very interesting paper by Boyle and colleagues from the March edition of the Archives of General Psychiatry titled ‘Effect of a purpose in life on risk of incident Alzheimer’s Disease  and Mild Cognitive Impairment in community dwelling older persons’ and which is freely available here. I think that there is some really good data in this paper and although coming to the paper a little sceptical at first, the researchers have put some strong arguments together. Firstly they have used a longitudinal design. Patients are broadly divided into those without cognitive impairment, those with mild cognitive impairment and those with Alzheimer’s Disease (AD). A battery of neuropsychological tests have been administered and a clinical team have made the diagnoses. Furthermore in those that developed AD a large percentage were confirmed at autopsy. Superficial examination of the purpose in life scale reveals a ten-item questionnaire which however has been validated in previous research and which has also been associated with an increase in life-expectancy. In this paper the researchers demonstrate the relationship between Mild Cognitive Impairment(MCI)/AD and purpose in life using three statistical approaches. The first is simply a comparison of those who developed AD with those that did not (and similarly for MCI). Although there are significant difference in the expected difference, the magnitude of the differences aren’t particularly large.

The second approach is a proportional hazards model. This produces some interesting results. Thus those with a high score on the purpose in life test were 1.5 x and 2.5 2.4 x more likely to remain free of MCI and AD respectively than those with a low score. Thirdly the researchers have also demonstrated that the rate of decline is slower in the group with higher score on the purpose in life test. What’s also interesting is that the researchers controlled for depressive symptoms in their analysis thus reasonbly excluding one obvious confounder. With a good sample size, thorough workup and confidence in caseness, the support of previous research for their purpose in life measure – the researchers have produced some very significant results and it will be very interesting to see further work in this area considering the potential implications. This also relates well to the emerging discipline of positive psychology (see here, here and here).

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