What We Know About Dementia Today
A wise man speaks about dementia.
Posted Apr 17, 2019
It's so hard to know these days what information is true, and what is just noise. Advice is everywhere. Wisdom is not. Today I offer an interview (edited) with a person who knows what he is talking about. He started out smart and then spent decades meticulously and intelligently studying dementia and its risk factors. He is Albert Hofman, M.D Ph.D., Chair of the Department of Epidemiology at the Harvard T.H. Chan School of Public Health in Boston, MA. I was lucky enough to interview him back in January. Dr. Hofman is a busy man; he was rushing to the airport to fly to Europe and still made time for our conversation.
T: You came to the US from the Netherlands, and are especially celebrated for your work on the Rotterdam study. Can you tell me about that?
AH: The study was launched in 1990. We now have 20,000 people we follow every three to four years, all in one district of Rotterdam [in South Holland]. They all come to the examination center, where we do very in depth, state of the art exams. We've followed many of these people for 25 years, and roughly 1600 have developed dementia. This is a very large study, the largest.
T: A dream for an epidemiologist.
AH: A cohort study like this gives us the best information. Medical records will miss some people who have a diagnosis; there is a lot of under-reporting of dementia, but in this cohort study we can correct for that.
T: We read that the overall number of people with dementia is going up, but at the same time the percent of people with dementia in older age groups is going down. How is this happening?
AH: We live longer; our overall life expectancy is going up. There is a decline in percent for the older age groups, but that doesn't prevent the overall number of people with dementia from rising. We are victims of our own success.
T: Is dementia more common in women? I hear different reports.
AH: The incidence is basically the same in men and women. However, the rate is going down more in men, and that makes the rate of dementia in women look higher. Women also live longer, which also makes the rate appear higher. My view is that the rate is going down in men because there has been more attention to cardiovascular health, more of a focus on preventing heart attacks in mid-life, and smoking cessation. We have not had that focus on cardiovascular health for women, so the rates of dementia did not decrease as much. It's sexism, really.
T: So we need better heart health, including for women, to improve our brain health. Many people work on getting their blood pressure lower, but your work shows blood pressure can be too low. Why is that a problem?
AH: Blood pressure is very interesting, especially variability. We looked at the blood pressure change in our cohort over many years. Those with the biggest change, up or down, have a much higher risk of dementia 20 years later. The more stable the blood pressure, the better. If you compare those with the highest variability, in the top 20%, to those with the most stable blood pressure, the lowest 20% of variability, those at the top have a 5 times higher risk for dementia. If you put together all the genetic risks we know for late onset dementia, it never comes to that. Risk changes with age, too. At age 50-70, higher blood pressure increases the risk of dementia, most likely through stroke. But from 70-75, lower blood pressure has the higher risk of dementia. Maybe the blood vessels are clogged and the pressure is too low to get past and deliver blood to the brain. The key thing is not always to get lower pressure, but to get stable blood pressure.
T: That's dramatically different from current US recommendations, which look only at lowering pressure and not at stability.
AH: Yes. We need modification by age. And there are many questions about how blood pressure interacts with other risk factors, like amyloid deposits and tau. I see a sequence like this: low blood flow to the brain, then neurons die, then we get plaques and tangles. We know from 30-40 trials that the amyloid hypothesis [that amyloid starts the process of dementia] is not working.
T: And we find many older people with amyloid, but no dementia.
AH: We knew that already, but we forgot.
AH: As an epidemiologist, I look at the population. Dementia is big. Depression is bigger; it’s everywhere. The question becomes, let’s look at dementia and depression and ask if they are related. Yes, they are. They hang together. There are overlapping factors causing both. It is not due to chance that many people with depression are also demented. To make a separation and say one is mental, one is not, it makes no sense. Neuroscience is bringing things back together, so there is less of a split between psychiatry and neurology.
T: I have a hard question. Suppose one day your doctor says you have dementia. What care would you want?
AH: (Pause. Laughs.) To be honest, I have not thought about it.
T: That is true of lots of experts in dementia.
AH: Even if they have dementia in their family, as I do.
T: Especially so.
AH: (Pause) I’d like to go on as long as possible, independently. I hope I’d have the right environment to stay home. I’d want to think about end of life decisions. In the Netherlands and Scandinavian countries there is open discussion [of aid in dying], but here and in Britain, it’s not possible to discuss. In some countries you can make clear your wishes, that you would not want to suffer, that you might want a physician’s help. For me that would be rational. Though I do know from colleagues that it is difficult to assist in suicide. I feel why that is. But that is part of what I would want.
In an era of ersatz expertise, it was a treat to meet a person who truly knows what he is talking about.
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