This chapter looks at some very basic factors that research indicates may be associated with an increased risk of dementia. The first of these is age. We hear so often that cases of dementia are increasing because we are living longer, but is this really the case?

Age and dementia

Whilst there are some quite striking examples of younger people developing dementia (particularly ‘familial’ dementia, which is examined on page 124), the most prominent ‘risk factor’ for developing the condition is indeed age. Dementia is a disease of older people. However, it is not an inevitable result of ageing. Many older people have excellent cognition, even taking into account the natural slowing down of life in general as we get older.

A person’s risk of developing dementia rises from one in 14 over the age of 65, to one in six over the age of 80. That is, one in 14 people over the age of 65 have dementia.1 Also, that five in six people over the age of 80 do not. What makes the difference between those who do have dementia symptoms and those who don’t? Let’s examine some of the factors that seem to play a part alongside age. Strikingly, research shows that personality and social factors are significant in this respect.

Personality, social factors and dementia

The Nun Study

David Snowdon, a US-based neurologist, has studied ageing and dementia in a population of 678 nuns. ‘The Nun study’, as it is known, is a most useful source for researchers because it is a longitudinal study (that’s a study that follows a group over a long period of time) of ageing and Alzheimer’s disease, which began in 1986 as a pilot study on ageing and disability. It started out using data collected from the older School Sisters of Notre Dame living in Mankato, Minnesota, but later expanded to include older Notre Dame Sisters living in the midwestern, eastern and southern regions of the United States. Participants in the Nun Study include women representing a wide range of functioning and health. Some Sisters are in their 90s; others may be in their 70s. Some are highly functional, with full-time jobs; others are severely disabled, unable to communicate, possibly even bed-bound.

Each of the 678 participants in the Nun Study agreed to participate in annual assessments of their cognitive and physical function. The assessments have included medical examinations and giving blood samples, and many of the nuns agreed to donate their brains after death for research. This means that the Nun Study represents the largest brain-donor population in the world. In addition, the Sisters have given investigators full access to their convent and medical records.

The study has found that traits in early, mid and late life have strong relationships with the risk of Alzheimer’s disease, as well as the mental and cognitive disabilities of old age. For example, among the documents reviewed as a part of the study were autobiographical essays that had been written by the nuns upon joining the Sisterhood. It was found that an essay's lack of complexity, vivacity and fluency was a significant predictor of its author's increased risk for developing Alzheimer's disease in old age. Roughly 80% of nuns whose writing was measured as lacking in ‘linguistic density’ went on to develop Alzheimer's disease in old age; meanwhile, of those whose writing was not lacking, only 10% later developed the disease.2

Social engagement

From personal experience of supporting clients with dementia, I have frequently noted the number who have told me, ‘I am not particularly sociable’. Another factor of note is the number of people who develop dementia shortly after retiring from full-time employment. It seems that in many cases the work in which they were involved was a significant factor in giving meaning to their life and it may have been the main social involvement that they had with others.

Research findings on personality

The suggestion that certain personality ‘types’ might be more prone to developing dementia has been studied elsewhere. A paper by Nicholas and colleagues, published in 2010, detailed the results of a case-control study which set out to examine whether personality traits and social networks were significant to the risk of developing Alzheimer’s disease (AD) specifically.3 This study examined 217 individuals diagnosed with probable late-onset AD (160 women and 57 men). For the purposes of this study, ‘informants’ who had lived with or were in regular contact with the people studied (the ‘subjects’) were asked to provide retrospective information about the personality of subjects and controls. The controls were recruited from the same population area and were mostly unaffected siblings of the subjects. The informants were asked to remember the subject they knew as she/he had been in their 40s. The subjects were, at the time of the research, aged between 61 and 98 years. Additional assessments were made about social activity when subjects had been in their 40s, and also the level of physical and mental challenge they would have experienced at that time. Cases and controls were also assessed for major depressive episodes and/or abnormal anxiety prior to the age of 50.

The results showed that a selection of abnormal personality traits was over-represented in those diagnosed with AD. The AD group had a significantly greater number of personality disorder traits compared with the control group. A high correlation was found particularly with what are classed as ‘cluster-A personality traits’ (paranoid, schizoid and schizotypal) and a lesser but significant correlation with ‘dissocial’, ‘borderline’, ‘histrionic’ and ‘narcissistic’ traits (all precise psychological terms). In some cases, the differences were particularly striking between those with AD and the controls (for example, some of those who later developed AD had few close friends, found difficulty in enjoying close friendships, bore more grudges, preferred solitary activity, had difficulty expressing feelings and were easily offended). Those people with AD also had sparser social networks than the controls.3

The researchers accepted that the main limitation of the study was that they employed a retrospective rating of personality and social activity so the findings may have been subject to recall bias. However, they concluded that: ‘There is an association between abnormal personality traits and AD. Individuals with AD also appear to have had lower levels of social interactivity.’

Long-term v. short-term personality traits

It is sometimes difficult to distinguish whether apparent personality traits are part of a long history or whether a solitary lifestyle and unwillingness to embrace new experiences are the result of recent life events. Doctors sometimes use a system of asking those closest to the person with dementia to describe his/her personality 10 years previously in order to assess how his/her personality traits might have changed. Of course, this is a very inexact method, relying as it does on memory which may be tainted by past life events and the particular relationship of the relative with the person being assessed. For example, if the person giving the assessment is a son or daughter of the patient, then their whole concept of the parent’s personality may be coloured by their experiences of that person when they were children. Conversely, if they are now in mid-life they may have only vague memories of their parent’s personality 10 years previously as they might have been living apart and heavily involved with their own young family.

Several questionnaires have been developed to make this assessment, but even the health professionals using them will admit their weakness and lack of objectivity.

Is personality fixed or fluid?

There is evidence that the brain is...