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A longitudinal studytracking high school students who had taken personality testsfound that certain traits appeared protective and were associated with less dementia more than 50 years later.

The first longitudinal study to look at the association between personality traits in adolescents and dementia 50 years later found that teens who were calmer, more mature, and energetic than their peers were less likely to be diagnosed with dementia, according to the findings published online in the October 16 issue of JAMA Psychiatry.

The findings shed light on the ongoing debate about whether personality patterns truly predate dementia pathology.

Because the study started in the 1960s when participants were high school students, we knew it was very unlikely that they would have dementia [at the time the study started]. We wanted to rule that out because previous studies that looked at personality traits associated with dementia enrolled older adults and studied them only five to ten years out. Therefore, it was possible that personality traits were early signs of the disease rather than true risk factors, lead investigator Benjamin P. Chapman, PhD, MPH, associate professor of psychiatry and public health sciences at the University of Rochester Medical Center told Neurology Today.

Neurologists who treat dementia and not involved in the study, said that the lengthy follow-up period confirmed the validity of the results.

It's jaw-dropping that the researchers collected data 50 years before most longitudinal research started on personality traits and obtained similar results. Because no known neurodegeneration occurs during adolescence, this establishes in my mind that personality traits are true independent risk factors for dementia in old age, said Robert S. Wilson, PhD, professor of neurological sciences at Rush University Medical Center and a neuropsychologist at Rush Alzheimer's Disease Center.

To study the association, the researchers conducted an analysis from March 2018 to May 2019 of data collected from 82,232 high school students who participated in a 1960 national personality study. Data was also collected from participants' Medicare fee-for-service claims between 2011 and 2013 that identified who was diagnosed with dementia based on the International Classification of Diseases, Ninth Revision (ICD-9) diagnosis code.

The sample was half female with a mean age of 15.8 at baseline and 69.5 years at follow-up, with an average span of 53.7 years. Three percent (2,543) of the total sample met dementia criteria during the study.

The 150-item Project Talent Personality Inventory covered ten common personality traits in high school students and beyond: vigor, calmness, mature personality, impulsiveness, self-confidence, culture, sociability, leadership, social sensitivity, and tidiness. These scales had scores that ranged from high to low.

Although the inventory was designed more than 50 years ago, recent research has shown that the scales highly correlate with modern ones such as the Big Five personality test for similar traits, said Dr. Chapman. For example, calmness has been highly (and negatively) correlated with neuroticism, a predictive trait for dementia, vigor with extraversion, and mature personality with conscientiousness.

The researchers measured socioeconomic status with a composite score based on parental educational level, income, occupation, and property ownership. Participants were also surveyed on demographic factors and height and weight.

The protective nature of calm and maturity against dementia was higher in teens with higher socioeconomic status. For example, the hazard ratio at 1 standard deviation (SD) of socioeconomic status was 0.89 (95%CI, 0.84-0.95; p<.001) for calm, and 0.90 (95%CI, 0.85-0.96; p=.001) for maturity.

Average socioeconomic status also had some protective associations: at a level of socioeconomic status 1 SD above the mean, adolescent calm and maturity were each associated with roughly a 10 percent reduction in dementia risk. A 1 SD increase in vigor reduced later-life dementia risk by about 7 percent, about the same as a 1 SD increase in socioeconomic status

The preliminary data suggest that young adults who are less stable emotionally and less conscientious are probably at greater risk of having dementia in later life. For clinicians assessing the risk of dementia, they may want to look at a person's life history to get a sense of what they were like before they started worrying about dementia, suggested Dr. Chapman.

The main limitation was the observational study design, which enabled only associations to be made, the study authors noted. Also, the follow-up period ended in 2013 before the participants reached their mid-70s when late-onset dementia can occur.

Dr. Wilson also noted that the findings are consistent with prior research that found being less neurotic and more conscientious were protective against dementia.

This suggests that clinicians consider interventions that might enhance those traits. We know that personality traits evolve during adulthood such as being more mature and responsible. Psychotherapy can help to increase those personality traits and reduce neuroticism.

He cautioned that dementia is multifactorial and that biological factors account for only half of them. While personality is a likely player, it's not clear how much it contributes to dementia. Dr. Wilson, whose research was the first to show that low conscientiousness predicted dementia, estimated that the trait most likely makes up less than 5 percent of possible causes.

He recalled being castigated by a widow whose husband had died from Alzheimer's disease (AD). She said he was the most conscientious person she'd ever known. That story illustrates the danger of expecting risk factors to be more powerful than they really are, especially when dealing with a chronic illness like dementia. It's premature to throw a lot of resources into interventions until we understand the mechanisms better, said Dr. Wilson.

Richard S. Isaacson, MD, associate professor of neurology at Weill Cornell Medicine who also directs the Alzheimer's Prevention Clinic at New York-Presbyterian/Weill Cornell, was not surprised by the findings.

After treating hundreds of patients of all ages at my clinic, I believe that behaviors throughout the lifespan can influence the course of dementia. In fact, early life risk factors, such as educational attainment and learning disabilities, may alter brain structure and/or function, increasing vulnerability to AD-pathology later in life.

For example, a person with a calm demeanor is more resilient to stress, which results in less cortisol and less acceleration of brain aging than someone who is very neurotic. Rumination, which is a central aspect of neuroticism leads to poorer cognitive outcomes, said Dr. Isaacson.

He pointed out that a mature and responsible person may be better able to mitigate life's stressors and that someone with vigor or high energy may be physically active as well as cognitively engaged, which can help protect against AD.

Dr. Isaacson suggested that neurologists incorporate more questions about early life risk factors, including personality traits, educational attainment (For example, years of education, class rank in high school) and learning disabilities (such as attention deficit-hyperactivity disorder or dyslexia) into risk assessments and then use those responses to better stratify risk.

For example, it would be interesting to have people complete a personality inventory and then undergo an intervention like mindfulness-based stress reduction, assess the outcomes, and stratify them based on personality traits to know who benefits the most from the intervention, he said.

Neurologists could also incorporate the findings into conversations with patients with moderate to high risk of dementia. Saying to patients in their 20s when personality traits are easier to modify, that a study showed that certain personality traits like neuroticism may lead to worse brain outcomes in mid-life or beyond, might motivate them to seek help from a psychologist or psychiatrist and try mindfulness or cognitive behavior therapy, said Dr. Isaacson.

Drs. Chapman, Isaacson, and Wilson had no disclosures.

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