There are lots of things that put people at higher risk for cognitive decline and dementia. Traumatic brain injury puts veterans at increased risk of dementia. Boxing and blows to the head can also increase the risk for Alzheimer’s disease. Low levels of vitamin B12 are a problem. There may also be diabetes-related dementia. What about a fast pulse? A new study suggests that a rapid heart rate may also be a risk for dementia (Alzheimer’s & Dementia: Journal of the Alzheimer’s Association, Dec. 3, 2021).
How Would You Know If You Are at a Risk for Dementia?
Many people do not want to know. We completely understand. The drugs for Alzheimer’s disease are not impressive. You read about the controversy surrounding Aduhelm (aducanumab) at this link. But what if you could modify your risk once you know what might put you at a risk for dementia?
Identifying people who are more likely to be susceptible to dementia will be even more important when there are medications that might actually delay or prevent it. A Swedish study suggests that a simple heart rate measurement could be a clue (Alzheimer’s & Dementia: Journal of the Alzheimer’s Association, Oct. 2022).
In the Swedish National Study on Aging and Care in Kungsholmen, scientists followed more than 2,000 individuals over 60 years of age. During the 12 years of follow-up, people with a resting heart rate of at least 80 beats per minute were 55% more likely to develop dementia than those whose resting heart rates were between 60 and 69 beats per minute.
The association remained even after adjusting for cardiovascular disease, a known risk factor for dementia.
Why Would a Rapid Heart Rate Be a Risk for Dementia?
Why did these Swedish researchers bother to study heart rate in the first place?
Here is their explanation:
“Abundant evidence has consistently shown that an elevated resting heart rate (RHR) predicts future CVD [cardiovascular disease] events beyond traditional CVD risk factors. A limited number of studies also show that a high RHR is associated with cognitive decline and dementia in the general population of middle-aged adults and in patients with ischemic stroke. However, this association has not been investigated in the general population of older adults. Besides, whether an increased RHR is independently associated with cognitive decline or the association is merely explained by the underlying CVDs has yet to be explored.”
A Rapid Heart Rate as a Risk for Dementia:
The important contribution of this study is that heart rate elevations above 80 beats per minute are an independent risk factor for dementia. In other words, this was not a byproduct of cardiovascular disease (CVD). Now, it is true that CVD is itself a risk factor for dementia. But a rapid heart rate was itself linked to cognitive decline without heart disease in the background.
One possible explanation is that a rapid heart rate could put stress on the walls of arteries. When arteries become stiff because of stress, there could be damage to small blood vessels in the brain.
Another possibility is that people with high heart rates may have an overactive sympathetic nervous system. In other words, they have a lot of adrenaline pumping through their bodies. That could be hard on the brain.
People with higher heart rates may be more likely to be couch potatoes. That is to say, they may not participate in much physical activity. People who exercise tend to have lower heart rates and less cognitive decline.
High levels of thyroid hormone circulating in the body can raise the heart rate. New research suggests that this might contribute to cognitive decline.
Excess Thyroid and Cognitive Decline:
When the thyroid gland produces too much or too little thyroid hormone, it can have profound effects on both body and mind. Many people are all too familiar with the brain fog associated with hypothyroidism, when thyroid levels are low. A new study published in JAMA Internal Medicine demonstrates that high levels of thyroid (thyrotoxicosis) also cause cognitive problems (JAMA Internal Medicine, Oct. 23, 2023). The researchers found this held true whether the problem was due to spontaneous hyperthyroidism (such as Graves disease) or to overtreatment for an underactive thyroid.
This study reinforces the importance of keeping thyroid hormone levels within the target range. The authors found that older people who had elevated levels of thyroid hormone due to hyperthyroidism or excessive levothyroxine doses were almost 40% more likely to be diagnosed with cognitive impairment.
Can You Change Your Heart Rate?
First, do not do this without checking with a physician. If your resting heart rate is above 80 beats per minute, you should check in with your primary care provider to try to figure out what is going on. For one thing, you might have hyperthyroidism. Or there may be some underlying heart arrhythmia.
Second, a doctor can advise you about a safe exercise program. There are also medications that can slow heart rate. A doctor can advise you if that might be a safe option.
The authors of this Swedish study suggest that we need a long-term study to determine whether:
“…a reduction in RHR [resting heart rate] through exercise or medical treatment may be explored as an intervention target to delay cognitive decline. Further intervention studies are needed to prove the potential beneficial effects of RHR reduction on cognitive outcomes.”
“Further research is needed to confirm our results and to explore the mechanisms at play in this association. Eventually, such evidence would lead to novel preventive strategies in the field of cognitive aging.”
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