Weekend Reads | Assessing Dementia Risk at Age 60

The number of Americans who have been diagnosed with dementia at age 60 is very small. But it grows exponentially from there, and among those who reach their 80s, it is a substantial portion of the population — by some measures, about 50%. A challenge, though, is that we don't have a good way to predict which people will develop dementia or other cognitive impairments in their advanced years. This weekend's read is a study by the nonprofit RAND Corporation in which the researchers attempted to predict who will ultimately develop dementia based on what we know of them at age 60.

The researchers analyzed data in the Health and Retirement Study (HRS), a long-term survey of Americans over the age of 50 that has collected data on nearly 70,000 people over its course. They looked at 181 potential risk factors across nine categories:

• Basic demographics, including sex, age, race and ethnicity, place of residence, place of birth, veteran and marital status.

• Socioeconomic and labor factors, such as educational level, employment history, income, and the characteristics of jobs held (e.g., physically, mentally, or emotionally stressing). 

• Lifestyle and health behaviors: smoking, exercise, getting regular flu shots or medical exams, etc.

• Parents' health status and history.

• Family composition and marital status history.

• Psychosocial information, such as ratings for specific personality traits, such as neuroticism, extraversion, and openness to experiences.

• Self-reported health information and functional limitations: how an individual rates their own health and describes any ailments or constraints they suffer from.

• Objective physical health measurements that were collected by medical staff as part of the HRS survey.

• Cognition measures collected by the HRS survey staff, including memory recall tests and other standard cognitive test results.

Plenty of the 181 factors at age 60 indicated at least a slightly increased risk for dementia at age 80, and they span the above categories. Being born in a southern state increases the risk; having a higher level of education or working for more years indicates a lower risk. Neuroticism marks higher risk; conscientiousness marks lower risk. Being disabled dramatically increases the risk of dementia.

Being less active — literally participating in fewer daily activities, as well as your amount of exercise — substantially increases dementia risk. Impaired physical abilities, such as walking, grip strength, and balance, increased risk. 

Lower scores on cognitive tests were some of the most definitive risk factors: If you did poorly on them at age 60, you have a substantially higher risk of dementia later.

But there are additional layers of complexity to this analysis, because many of the factors are interrelated and can't be teased apart. For example, Black and Hispanic people have a higher risk for dementia, but if you factor out differences in socioeconomic status, then race is no longer predictive of dementia. As mentioned earlier, people born in southern states have a higher risk, but southern states have a larger number of people in a low socioeconomic status, as well as larger Black populations. Physical impairments might limit a person's ability to exercise and maintain good physical health; likewise, cognitive impairments might limit participation in activities that exercise the brain. 

And then there is the issue of causality — and which direction it might run. People who work for more years have a lower risk of dementia; but does working longer prevent or delay dementia? Or does lack of dementia allow people to work for more years? Or are both dementia and how long one can work controlled by some other factor? Similarly, staying active and in good physical health correlates to lower dementia risk, but we don't know if physical health delays dementia or if lack of dementia (or its underlying causes) improves physical health and allows for more activity. The conventional wisdom is that staying physically and mentally active prevents or delays dementia and general cognitive decline, but the data doesn't actually prove that there is a cause-and-effect relationship between them.

Some of the factors are worthy of our attention because they are at least partially under our control, even at age 60. We can't change where we were born, but we can change how much physical activity and mental stimulation we get throughout our lives. It's one thing to be able to predict our future risk of dementia at age 60; it's another to be able to make changes in our lives that lower that risk. Interestingly, both excessive alcohol consumption and completely abstaining from alcohol were associated with higher dementia risk; low-to-moderate consumers had the lowest risk. 

It would be nice if a study like this gave us nice, clean answers; unfortunately, it doesn't. The results are messy, the risk factors are deeply entangled with each other, and many questions remain. That said, the study is still useful. It tells us something about how much risk of future dementia a person faces at an age where they can at the very least prepare for it and, quite possibly, take steps to decrease the risk or delay the onset. And for a few of the factors, the results are clear: If you are already seeing some cognitive impairment at age 60, you'd better start making a plan.

Identifying Early Predictors of Cognitive Impairment and Dementia in a Large Nationally Representative U.S. Sample