Last week, I wrote about a dementia risk score developed by researchers at the Karolinska Institute in Sweden. To put the risk score in perspective, I checked in with Dr. Tiia Ngandu, co-author of the risk score article published in the September issue of Lancet Neurology. Here are her answers to my questions:
Q: Some background information: my dad died of a hemorrhagic stroke last November, and his autopsy showed severe cerebral amyloid angiopathy (CAA) along with probable Alzheimer's disease. He had few of the risk factors I think were involved in calculating the "dementia risk score": his cholesterol was always low, he was not at all overweight, his blood pressure was low, he exercised and had 16 years of education. So, in my father's case, anyway, he would have had a low score, and I think would have been a "false negative" in your study.
A: First of all, I would like to say that the aim of our risk score was not to say definitely that someone will develop dementia or someone will not. That would not be possible, since we are dealing with a disease that is as complex and multifactorial as Alzheimer's disease. Those persons who had more risk factors had a higher risk of developing dementia in 20 years time, but even among those who had the worst risk score, only 35 % developed dementia - that is to say that with our score it is not possible to "label" persons into future demented and nondemented. We hope that the risk score will be more used to inform both physicians and patients about the risk factors behind dementia in a very practical way. We believe that the persons with most risk factors and highest risk score might benefit from both lifestyle and pharmaceutical interventions.
Q: Was a fairly homogeneous population used for the study? [I asked this because results from one population may not apply to another.]
A: All the participants are from Eastern Finland, and they were fairly homogeneous population.
Q: Did you differentiate at all among the various types of dementia? What cognitive or other tests were used to detect dementia?
A: We differentiated between different types of dementia. The majority of patients had AD. The Mini Mental State Examination (MMSE) was used as a screening test, and after screening the patient went through both clinical and neuropsychological examinations. Due to the use of MMSE at the screening, we may have missed persons with mild dementia, especially early vascular dementia.
Q: Were there risk factors considered that were not found to be predictive in this study? Smoking? Family history of dementia? Tooth loss? Genetic status?
A: Risk factors that were considered but not found predictive were midlife smoking and diastolic blood pressure. We did not have information on family history of dementia or tooth loss. ApoE4 was predictive in this study and it was included in a second risk score model. (It was left out from the first one because we wanted to include only parameters that are easily available in primary care settings)
Q: What other risk factors may be considered while you refine the scoring process?
A: Other risk factors that should be considered in the future risk scores are at least diabetes and family history of dementia: those factors have quite a lot of evidence behind them at the moment.
Q: I saw an abstract of a presentation by researchers at Kings College London at the recent Alzheimer's conference in Madrid that says that in the Honolulu Asia-Aging Study, "cholesterol levels in men with dementia, and in particular those with Alzheimer’s disease, had declined at least 15 years before the diagnosis and remained lower than men without dementia throughout that period." Do you think this is true in other populations? How might this affect the cholesterol component of your risk score?
A: Some studies have shown that the cholesterol levels (as well as blood pressure levels) decline in demented patients, and that this decline begins already before the diagnosis of dementia can be made. This decline is probably due to the disease process rather than the decline in cholesterol increasing the risk of dementia. In the Honolulu-Asia Aging Study this kind of decline was observed already 15 years before diagnosis. Also the research group from the Honolulu study thought that the decline might be due to early stages of dementia. I don't see that these findings are in any way contradictory to our findings that high cholesterol levels at midlife would increase the risk of dementia. One should keep in mind the trajectories of cholesterol change with aging and in relation to chronic diseases.
Q: The audience for my blog is mostly middle-aged people, many of whom are caregivers for dementia patients. On a practical level, is there anything we should learn from the dementia risk score other than a confirmation that cardiovascular health and education levels appear to be linked to dementia?
A: What I believe that a middle-aged person could learn from our risk score is that there are several things one can do in order to reduce the risk of dementia. Especially the cardiovascular risk factors can be modified with both lifestyles and medications. I think it is quite good news for those who worry that they might become demented and would like to do something to prevent or postpone it. Of course there are still many other and also unknown factors influencing the development of dementia, but we believe that this is a step in the right direction.