Your personality traits as a teen may predict your risk of developing dementia

0
95

For the first time, a study has shown that personality traits as a teenager may predict dementia risk over 50 years later.

The study, led by researchers at the University of Rochester, was published in JAMA Psychiatry.

Previous studies have shown a link between early thinking abilities and later dementia. Other studies have also shown personality changes around the time when brain abnormalities can first be detected, but before thinking and memory are impaired.

The current study, which was funded by NIA, set out to examine the effects of personality traits measured many decades before dementia begins to develop and long before it can be diagnosed.

The researchers obtained data from 1960 for Project TALENT, the largest national sample of high school students.

At baseline, when the tests for 10 personality traits were administered, the average age of each participant was about 16. After examining Medicare records for more than 82,000 people who had participated decades earlier in Project TALENT, the researchers found that 2,543 met criteria for dementia by an average age of about 70.

The analysis showed that the relative risk of being diagnosed with dementia in later life was lower for teens who had higher levels of vigor, which was linked to having an energetic disposition, vitality and a high level of physical activity.

The traits of calmness and maturity were also associated with a lower risk of dementia later. Not associated with a dementia diagnosis were personality traits like social sensitivity, sociability and leadership.


The analysis showed that the relative risk of being diagnosed with dementia in later life was lower for teens who had higher levels of vigor, which was linked to having an energetic disposition, vitality and a high level of physical activity.

The researchers also evaluated the influence of socioeconomic status on the students’ personality test results. Socioeconomic status did not influence the results observed for vigor. But for higher levels of socioeconomic status, the protection from dementia from calmness and maturity increased.

t lower socioeconomic status, these two personality traits did not reduce risk for a dementia diagnosis.

The authors noted that this finding suggests that lower socioeconomic status is linked to higher chronic stress, which could eliminate the benefits of traits like being calm and mature.

As these older adults continue to age and even more of them develop dementia, additional studies can be conducted to examine the risk for dementia from having certain personality traits at age 16.

Additional and stronger evidence for vigor, calmness and maturity as protective personality traits could provide the basis for behavioral modification prevention studies.

Funding: This research was funded by NIA grant R01AG053155.


Dementia risk.

Other than rare cases caused by specific genetic mutations, AD is a complex, multifactorial disease. Age is the strongest risk factor for AD, with increasing incidence from 1–2% for individuals aged 60–65 to about 30% for those over the age of 85. The e4 variant of the APOE gene is another strong risk factor, increasing the risk by 8- to 12-fold in e4 homozygous individuals compared to non-carriers.

Other prominent risk factors can be grouped broadly under cardiovascular (e.g., midlife obesity, midlife hypertension, and diabetes), behavioral (e.g., smoking and physical inactivity), and psychosocial (depression, social contact, and education) risk (Beydoun et al., 2014Chuang et al., 2015Whitmer, Sidney, Selby, Johnston, & Yaffe, 2005).

Personality traits have robust links with psychological, behavioral, and clinical risk factors for AD (Chapman, Roberts, & Duberstein, 2011Hampson, 2012). For example, neuroticism is a strong risk factor for major depression (Kendler, Gatz, Gardner, & Pedersen, 2006) and conscientiousness is related to cigarette smoking, physical inactivity, and obesity (Sutin et al., 2016). Personality traits are also related to educational achievements, coping skills, and the quality and quantity of interpersonal relations, which in turn are associated with increased vulnerability to dementia (Beydoun et al., 2014Crooks, Lubben, Petitti, Little, & Chiu, 2008).

These links have led to the hypothesis that personality traits are associated with the risk of developing AD and related dementias. A recent meta-analysis (Terracciano et al., 2014) summarized the results of five prospective studies that included up to 5,054 individuals (Duberstein et al., 2011Terracciano et al., 2014Wilson et al., 2006Wilson et al., 2005Wilson, Schneider, Arnold, Bienias, & Bennett, 2007). At baseline, individuals free of cognitive impairment completed a self-report version of the NEO personality questionnaire. These individuals were then followed over time to investigate whether personality traits predicted who developed clinical dementia.

There was consistent evidence that individuals who scored higher on neuroticism or lower on conscientiousness had greater risk of incident AD. Although there was weak evidence for an association in the individual studies, the meta-analysis indicated that higher openness and agreeableness were associated with a slightly reduced risk of AD. Extraversion was unrelated to AD risk. The effects of neuroticism and conscientiousness were independent of each other and there was not an interaction between the two traits (Terracciano et al., 2014Wilson et al., 2005).

Two studies examined the facets of neuroticism and found that anxiety and vulnerability to stress were significant predictors of incident AD (Terracciano et al., 2014Wilson, Begeny, Boyle, Schneider, & Bennett, 2011). Two studies that examined the facets of conscientiousness found that several of its facets predicted incident dementia, with low self-discipline and responsibility being the strongest predictors (Sutin, Stephan, & Terracciano, in pressTerracciano et al., 2014).

The effect of neuroticism and conscientiousness are not just consistent across studies, but are also of non-negligible magnitude. In the Religious Order Study (Wilson et al., 2007), for example, those scoring in the bottom 10% of conscientiousness had about double the risk of AD as compared to those in the top 10%.

Similarly, in the Baltimore Longitudinal Study of Aging (Terracciano et al., 2014), individuals with scores in the top quartile of neuroticism or the lowest quartile of conscientiousness had a three-fold increased risk of incident AD. These effect sizes are similar or larger than those found for cardiovascular and behavioral risk factors, such as diabetes, midlife obesity, midlife hypertension, lower education, physical inactivity, and cigarette smoking (Barnes & Yaffe, 2011Daviglus et al., 2011).

Cognitive performance, decline, and impairment.

Consistent with prospective studies that examined incident AD, personality traits are associated with cognitive decline and mild impairments that can culminate in dementia. A large study of 4,039 members of the Swedish Twin Registry found neuroticism, but not extraversion, to be associated with cognitive impairment status 25 years later (Crowe, Andel, Pedersen, Fratiglioni, & Gatz, 2006). In cognitively healthy older adults, personality traits have been associated with the level of cognitive performance and rate of cognitive decline (Caselli et al., 2016). For example, in the Health and Retirement Study (N=13,987), individuals who scored lower in neuroticism or higher in openness and conscientiousness performed better on a memory task (Luchetti, Terracciano, Stephan, & Sutin, 2015).

A meta-analysis indicated that higher neuroticism and lower conscientiousness were associated with steeper cognitive decline over time. Although the association between personality and cognitive decline over short follow-up periods was small, the effects were stronger than the effect of cardiovascular conditions, physical inactivity, and history of smoking and psychological distress (Luchetti et al., 2015). The protective effects of high conscientiousness are particularly strong in predicting the rate of cognitive decline within the last three years before death compared to the pre-terminal decline (Wilson et al., 2015).

Finally, personality is also associated with subjective cognition. Individuals who score higher in neuroticism or lower in conscientiousness report more cognitive complaints (Steinberg et al., 2013) and worse self-rated memory (Luchetti et al., 2015). Subjective cognitive complaints are associated with increased risk of incident AD (Geerlings, Jonker, Bouter, Adèr, & Schmand, 2014).

Personality Disorder.

In addition to normal personality traits, personality disorders have also been associated with dementia. Most of this evidence is from studies with retrospective assessments by family members. Obsessive–Compulsive Personality Disorder, for example, is associated with increased risk of AD (Dondu, Sevincoka, Akyol, & Tataroglu, 2015); other studies report associations with almost all personality disorders (e.g., Nicholas et al., 2010).

Pathways Linking Personality to Dementia

Mechanisms.

As mentioned above, personality traits are related to multiple lifestyles and health factors that increase risk of dementia, and these factors are potential behavioral and clinical mechanisms through which personality is associated with dementia risk.

In particular, personality may contribute to risk of dementia by shaping over the lifetime an individual’s reactions to stress, health behaviors, and engagement in physical, cognitive, and social activities.

The finding that personality is associated with inflammatory markers (Luchetti, Barkley, Stephan, Terracciano, & Sutin, 2014) and brain-derived neurotrophic factor (Terracciano et al., 2011) suggests potential biological pathways.

Still other studies have tested to what extent the association between personality and incident AD or cognitive decline was accounted for by other risk factors such as education, APOE genotype, activity patterns, or vascular conditions. Although attenuated, the associations between personality and cognition-related outcomes generally remained significant when accounting for such factors (Luchetti et al., 2015Sutin et al., in pressTerracciano, Stephan, Luchetti, Albanese, & Sutin, 2017bWilson et al., 2003Wilson et al., 2007).

Some studies control for measures of distress or depressive symptoms when examining neuroticism as a predictor of incident AD (Johansson et al., 2014), but these findings are difficult to interpret given the conceptual and measurement overlap between neuroticism and other measures of distress. Rather than confounding factors, the psychological, behavioral, and clinical variables are likely to be partial mediators, and thus mechanisms, of the association between personality and incident AD.

Moderators.

A few studies have tested whether personality interacts with other risk factors to modulate the effect of personality on cognitive outcomes. Neuroticism, for example, may moderate the effect of the APOE genotype on cognitive function and risk of dementia (Dar-Nimrod et al., 2012). Other studies, however, found different (Sapkota, Wiebe, Small, & Dixon, 2015) or no interactions (Terracciano et al., 2014). Personality may also interact with the environment to predict dementia risk (e.g., inactive or socially isolated lifestyle, Wang et al., 2009), but to date there is no robust evidence that the associations vary across demographic groups defined by age, sex, race, ethnicity, or education (Terracciano et al., 2017b).

Reverse causality.

Behavioral and personality changes are a common clinical sign of AD (McKhann et al., 2011), and changes in the pre-clinical phase could be responsible for the observed associations between personality and incident dementia. This reverse causality hypothesis is plausible because the neuropathological change in AD occurs years before dementia onset (Jack et al., 2013).

The accumulation of amyloid-β (Aβ) and tau leads to neuronal dysfunction and cell death, which spreads through the brain and is manifested in the clinical symptoms. Cerebrospinal fluid (CSF) and position emission tomography (PET) amyloid imaging indicate that Aβ accumulation occurs about a decade or more before clinical manifestation of the disease (Buchhave et al., 2012Resnick et al., 2015).

While there is a delay in the onset of cognitive impairment, it is possible that personality change occurs earlier. For example, individuals who later developed AD were cognitively normal but may have some Aβ deposition at the time they completed the personality questionnaire.

The cascading neurodegeneration may have an impact on their brain and potentially their personality before the onset of cognitive symptoms. Of note, many studies on personality and incident AD were based on cohorts of older adults (mean age > 70 years) and had relatively short follow-up periods (≤6 years). As such, those who developed dementia during the follow-up period were likely in the AD prodromal phase when the personality questionnaire was completed.

Although plausible, there is clear evidence against the reverse causality hypothesis. A recent long-term prospective study (n = 2046) examined repeated NEO personality assessments over a time span of up to 36 years (Terracciano, An, Sutin, Thambisetty, & Resnick, 2017a). It found that the personality trajectories of those who developed AD were not significantly different from those who remained cognitively normal.

Even within the last few years before the onset of MCI or dementia, the study found no evidence of preclinical changes in personality that could be interpreted as an early sign of AD (but see, Balsis, Carpenter, & Storandt, 2005Duchek, Balota, Storandt, & Larsen, 2007). Other evidence against the reverse causality hypothesis includes findings that personality is associated with cognitive performance and predicts cognitive decline in relatively young samples (e.g., mean age = 45 years in Hock et al., 2014).

Personality resilience in the presence of AD neuropathology.

As noted above, Aβ dysregulation occurs years before the onset of dementia, and 20–40% of clinically normal older adults have biomarker evidence of AD neuropathology (Jack et al., 2013Sperling et al., 2011).

There is also considerable variability in the time lag between the emergence of AD neuropathology (e.g., positive PET amyloid imaging) and the onset of clinical dementia. Consistent with biomarker evidence, about 30% of individuals without cognitive impairment before death are found to meet the neuropathological criteria of AD at autopsy (Balsis et al., 2005Driscoll & Troncoso, 2011).

Personality traits may moderate the emergence of clinical signs of dementia in individuals with AD pathophysiology. We tested this hypothesis by comparing the personality traits of those who developed dementia with those who did not despite being found at autopsy to meet criteria for AD neuropathology.

Compared to those with clinical dementia, asymptomatic individuals (those with AD neuropathology but no clinical dementia) scored higher on conscientiousness and lower on neuroticism (Terracciano et al., 2013).

These findings suggest that a resilient personality profile plays a significant role at the interface of neuropathological processes and the manifestation of clinical symptoms. In people with underlying AD neurodegeneration, personality traits may help postpone the onset of clinical signs.

Research with in vivo biomarkers (CSF or imaging) and concurrent personality assessments in large prospective studies is needed to confirm this hypothesis. Such research would also help clarify the temporal progression of personality change that occurs with the onset of other clinical signs and the evolution of AD biomarkers.

The evidence is mixed on the link between personality traits and neuropathology at autopsy. Higher neuroticism has been associated with more advanced spread of neurofibrillary tangles in limbic and neocortical regions, as indexed by Braak staging, but not with levels of Aβ plaques (Terracciano et al., 2013); other studies have found no association with neuropathology at autopsy (Wilson et al., 2003Wilson et al., 2007).

Data from in vivo brain imaging, indicates that individuals with MCI who score higher in neuroticism or lower in conscientiousness have more severe white matter lesions, but not cerebrovascular lesions or medial temporal lobe atrophy (Duron et al., 2014).

In a large community-based cohort of about 500 older adults, individuals who scored lower in conscientiousness had more white matter hyperintensities, white matter fractional anisotropy, and brain-tissue loss (Booth et al., 2014).


Source:
NIH/NIA

LEAVE A REPLY

Please enter your comment!
Please enter your name here

Questo sito usa Akismet per ridurre lo spam. Scopri come i tuoi dati vengono elaborati.