Tuesday March 2 2010
The relationship with outlook needs more research
“Elderly people with a strong sense of purpose in life face a reduced risk of developing Alzheimer's disease,” The Daily Telegraph reports. The finding comes from research that assessed the outlook on life in 900 elderly people, following them for several years to see which of them developed cognitive problems.
This study had a number of strengths including good data collection methods and thorough assessments of its participants’ mental functions. It also adjusted for the influence of factors that might affect results.
The research does seem to show a link between a perceived greater purpose in life and reduced risk of Alzheimer’s. However, it is difficult to say whether purpose in life directly affects Alzheimer’s risk, if outlook is altered during the early onset of cognition problems or if another related factor is behind the link.
In addition, a person’s ‘purpose in life’ is likely to change at various points in their life depending on their circumstances, and a single assessment at the age of 80 may not fully capture this. Future studies need to confirm and further investigate any potential link between purpose in life and risk of Alzheimer’s disease.
Where did the story come from?
Dr Patricia Boyle and colleagues from the Rush Alzheimer’s Disease Centre in Chicago, Illinois carried out this research. The study was funded by the US National Institute on Aging, the Illinois Department of Public Health, and by the Robert C. Borwell Endowment Fund. The study was published in the peer-reviewed medical journal, Archives of General Psychiatry.
The Daily Telegraph gives an accurate and balanced account of this study.
What kind of research was this?
This was a prospective cohort study assessing the relationship between perceived purpose in life and the risk of mild cognitive impairment or Alzheimer’s disease. This study was part of the Rush Memory and Aging Project, which enrolled participants from 1997 to 2008.
The study design employed in this research is the best model for investigating this type of relationship, where it is not possible to randomise participants to ‘receive’ a perception of having a purpose in life, unlike a study on acupuncture, for example, where participants could be randomly chosen to receive the treatment as part of the study.
Collecting data prospectively means that the information gathered is more likely to be of greater accuracy than if the researchers had reviewed medical records to identify outcomes or relied on individuals recalling what happened in the past.
As with all observational studies, a potential limitation is that in addition to the factor being investigated, the results could be affected by any other factors that are not balanced between the groups. Therefore studies such as this need to consider these differences in their analyses.
What did the research involve?
The research included 951 community-dwelling older persons without dementia (average age 80.4 years) who were enrolled in the Rush Memory and Aging Project. Most of the participants were females (74.9%) and white (91.8%).
At their annual assessments, the participants had thorough neurological and cognitive function testing. All data was reviewed by an experienced Neuropsychologist, who determined if cognitive impairment was present, and by an expert clinician who gave diagnoses of probable Alzheimer’s disease (AD) according to recognised criteria.
Mild cognitive impairment (MCI) was diagnosed in individuals who had cognitive impairment but did not meet criteria for dementia. Just over a quarter of participants (26.6%) had mild cognitive impairment at the start of the study. The researchers reported that another study on the same population confirmed 90% of the diagnosed cases of AD through post-mortem.
The participants’ purpose in life was assessed in 2001 and then they were assessed annually for seven years (four years on average), to see if they developed AD.
Purpose of life was defined as “the tendency to derive meaning from life’s experiences and to possess a sense of intentionality and goal directedness that guides behaviour”. It was assessed using a 10-item scale derived from a longer questionnaire. Participants rated their level of agreement with ten statements, such as: “I feel good when I think of what I have done in the past and what I hope to do in the future.” ; “I have a sense of direction and purpose in life.”; and “I sometimes feel as if I have done all there is to do in life.” An average score was obtained for each participant, with higher scores indicating greater purpose in life. The researchers then looked for relationships between purpose in life and disease onset.
Analyses were adjusted for a number factors that could affect results, including age, sex, education, depressive symptoms, neuroticism, social network size, and number of chronic medical conditions. The researchers also carried out additional analyses that either excluded people who developed AD in the first three years of the study (as these individuals may already have had mild undiagnosed AD at the start of the study) or excluded those with MCI at study start to look at risk of developing MCI.
What were the basic results?
During the seven years of follow-up, 155 participants (16.3%) developed Alzheimer’s disease.
The risk of developing Alzheimer’s disease during follow-up was significantly lower in people with a greater sense of purpose in life, even after taking into account age, sex, and education (hazard ratio [HR] 0.48, 95% confidence interval [CI] 0.33 to 0.69).
People with the highest 10% of purpose in life scores were 2.4 times more likely to remain free of Alzheimer’s disease than people with the lowest 10% of purpose in life scores. These results remained statistically significant after taking into account other factors that may have contributed (depressive symptoms, neuroticism, social network size and number of chronic medical conditions), and after excluding individuals who developed AD in the first three years of the study. There was no relationship between purpose in life and demographic characteristics.
People with greater purpose of life scores were also less likely to develop mild cognitive impairment, and had a slower rate of cognitive decline than those with less purpose in life
How did the researchers interpret the results?
The researchers concluded that “greater purpose in life is associated with a reduced risk of [Alzheimer’s disease] and [mild cognitive impairment] in community-dwelling older persons”. They suggest that “purpose in life is a potentially modifiable factor that may be increased via specific behavioural strategies that help older persons identify personally meaningful activities and engage in goal-directed behaviours”.
This research suggests a link between purpose in life and risk of cognitive impairment and Alzheimer’s disease. There are some points to note on this research:
- As with all observational studies, it is possible that factors other than the one of interest have affected the results. During their analysis, the researchers took into account a range of these potential ‘confounding’ factors, which increases reliability of results. However, other unknown or unmeasured factors, such as an apathetic outlook, could be having an effect. The researchers acknowledge that their ability to say whether purpose in life is actually causing the reduction in Alzheimer’s risk is limited.
- It is possible that some of the participants had already started to develop Alzheimer’s disease when the study started. If the undetected condition changed the way participants perceived their purpose in life, it may have affected the study’s results. To reduce the impact of this the researchers carried out analyses excluding those who developed Alzheimer’s early in the study, and looked at whether purpose in life was related to MCI. However, it is still possible that very early undetected brain changes are present in those who went on to develop Alzheimer’s.
- The study consisted mainly of white females, who were recruited from continuous care retirement communities and subsidised senior housing facilities. The results may not apply to different elderly population groups.
- A person’s perception of their ‘purpose in life’ is likely to change depending on their life circumstances. It is not clear whether a single assessment of this question at the age of 80 is representative of their purpose in life over their lifetimes, or whether it is only an individual’s feelings about their purpose in the latter decades of their life that could have an influence on their AD risk.
Future studies will be needed to confirm these results and to determine whether purpose in life can be modified and whether this has an effect on risk of Alzheimer’s disease.