JOHN YANG: A new study shows that Americans risk of developing dementia at any time after turning 55 is more than double what earlier research found.

The New York University study estimates that the number of dementia cases will double by 2060, reaching 1 million new diagnoses each year.

Dr. Josef Coresh is the director of the Optimal Aging Institute at NYU's Langone Health System.

He's also one of the authors of the study.

Dr. Koresh, how significant is the findings?

DR. JOSEF CORESH, NYU's Langone Health System: I think it's important for all of us, right.

Because if you're thinking about your lifelong health, it makes you realize that you need to consider the risk that at some point you may hit dementia before death.

JOHN YANG: And what accounts for the higher risk?

JOSEF CORESH: So basically, we did a study that was more diverse in more centers and spanned both white and black Americans.

And we also spent an enormous amount of energy to make sure we captured all of the cases.

And then the population has gotten older.

So as life expectancy has gotten older, the risk is higher.

So the risk by age 75 is 4 percent.

By age 85, it's 20 percent And by age 95, it rises to the full 42 percent chance of getting to dementia before death.

But more than half the risk is after age 85.

JOHN YANG: So I just want to make sure I understand this is because the population is aging.

It's not that something has changed about dementia.

JOSEF CORESH: Exactly.

The population in the U.S. is aging.

And that is also the reason that we expect the number of new dementia cases to double between now and 2060.

It's also true that our estimate of the incidence, the risk, is higher than the previous estimate.

But I think our estimate aligns with the current estimate of the number of people we have in dementia in the U.S. which is about 6 million people.

And the old estimate of risk needed to be adjusted, it was about twofold too low.

JOHN YANG: Who's most at risk for developing dementia?

JOSEF CORESH: So when you get to 42 percent, you're really talking about all of us.

When you talk about earlier onset, Black Americans are at higher risk.

People who are genetically susceptible with a gene called APOE e4 alleles are at higher risk.

So that risk manifests before the age of 75.

And then women, because they have a lower risk of mortality, get to the more advanced ages.

And as we said, more than half the risk is after age 85.

And women are more likely to get there, so they have a higher lifetime risk.

JOHN YANG: Why is the higher risk among black Americans?

JOSEF CORESH: So among black Americans, I think we'll get to the fact that the Lancet Commission estimates that about half the risk of dementia is preventable.

The factors include more education and better quality education at early life and creating cognitive reserve.

And the black participants, particularly the ones in this study, which were often from Jackson, Mississippi, probably had fewer educational opportunities.

The other thing that's happened is vascular risk factors are connected to dementia risk.

And so the black participants had more hypertension, more diabetes, more obesity, and possibly somewhat less treatment for those conditions, increasing their risk.

JOHN YANG: Is the health care system ready for this surge in dementia cases?

JOSEF CORESH: I think we're already struggling with the number of dementia cases we have.

I think we need to think about how to adjust to our aging population, which would include both trying to reduce the risk of dementia through some of the risk factors I talked about.

And then we need to make sure older adults are allowed and able to stay productive and are not socially isolated, which is another risk factor for dementia.

And then at the oldest ages, we will need more ability to have care and partnerships between care facilities, care team, healthcare teams and families.

So there is a lot of work to do.

JOHN YANG: It's very interesting.

What is the link between hearing and developing dementia?

JOSEF CORESH: So we've spent quite a bit of time on that.

It is clear that people who have hearing loss and hearing loss increases dramatically with age, much like dementia, are at an increased risk of dementia.

And last year we published a large randomized study which showed that in the first three years, if you're at high risk of having cognitive decline, hearing aids with a proper fitting and several times to make sure you really use them, the majority of the people found them to be transformative, improving their quality of life and reduce their rate of cognitive decline by 48 percent.

JOHN YANG: What are some of the other mysteries of dementia that researchers are still trying to unlock and answer?

JOSEF CORESH: I think the biggest thing for us is the focus on late onset dementia after age 85.

Because we have more than half the cases of dementia, the number of years with dementia is lower.

But it's really important both societally and in terms of quality of life and engagement.

I do think that we should spend a little time on the good news that over the last 10 to 20 years we've realized that a lot of dementia risk is preventable.

JOHN YANG: Talk about what can be done to prevent it.

JOSEF CORESH: Yeah.

So the Lancet Commission has a wonderful report that names 14 different risk factors.

I'm not sure I'll hit them all, but early in life we talked about more education to create cognitive reserve.

You want to avoid traumatic brain injury, both early, middle and late life sports injuries and later in life falls.

Once you hit your head hard enough, you need to allow your brain to recover or otherwise you have an increased risk of dementia.

In midlife and later, vascular risk factors prevent diabetes, no smoking, less alcohol, blood pressure control and low blood pressure is critical.

Cholesterol and obesity, as you get later in life, sensory losses, hearing and vision, correcting those should really help.

And as you get to very late in life and even earlier, social isolation, depression, addressing those issues and then later teamwork in terms of caring for people can allow lots of people, even with the onset of dementia, the majority of people in early stages stay at home, can be cared for by family members and with the correct teamwork and medication, be managed quite well.

JOHN YANG: Very interesting.

Dr. Joseph Coresh, thank you very much.

JOSEF CORESH: My pleasure.

Thank you for having me.