A recent study conducted at the Karolinska Institutet, in Sweden, suggests that individuals aged 60 years or older with an elevated RHR have an increased risk of dementia and accelerated cognitive decline. This relationship was independent of other risk factors associated with cardiovascular disease.
A small number of studies show an association between a high RHR and dementia or cognitive decline in the general population of middle-aged adults and people with ischemic heart disease. However, until now, researchers had not investigated this association in the general population of older adults.
The new study, which appears in the journal Alzheimer’s & Dementia, addresses this gap. The scientists followed 2,147 participants living in Stockholm for up to 12 years. Their mean age was 70.6 years, and 62% were women.
The researchers measured RHR using a standard electrocardiogram, and they assessed global cognitive function with a mini-mental state examination.
They also collated information about other factors, including age, sex, education level, physical activity, and smoking status. Additionally, the scientists noted participants’ body mass index and cholesterol levels.
A significant link
Individuals whose RHRs were 80 beats per minute (bpm) or higher had, on average, a 55% higher risk of developing dementia than those with RHRs of 60–69 bpm.
The association between elevated RHR and cognitive decline remained significant, even after taking into account factors such as current cardiovascular disease, age, sex, education level, behavioral factors, and medications.
Although this study could not establish a causal relationship, it did offer a plausible explanation for the link between an elevated RHR and cognitive decline.
The lead author, Dr. Yume Imahori, observes, “If we follow such patients’ cognitive function carefully and intervene early, the onset of dementia might be delayed, which can have a substantial impact on their quality of life.”
Medical News Today spoke with Dr. Ian Neel, a gerontologist and associate clinical professor of medicine at the University of California, San Diego, who was not involved in the study. He said:
“There is a strong link between heart health and brain health. The Alzheimer’s Association has acknowledged this concept through their recommendation for physical activity with cardiovascular exercise in an effort to reduce the risk of cognitive decline. This study helps add strength to this recommendation, using heart rate as a marker for heart health.“
Dr. Neel continued, “It is important not to assume that a low heart rate will reduce [the] risk of dementia, but rather [to] take away from this study that good heart health is associated with a lower risk of cognitive difficulties.”
Other interesting possibilities
The authors discuss possible mechanisms by which a high RHR might increase a person’s dementia risk.
They consider underlying cardiovascular diseases, such as atherosclerosis, imbalances in the sympathetic and parasympathetic nervous systems that innervate the heart, tiny circulating blood clots, and a lack of good circulation to the brain.
It is important to note that scientists have yet to investigate whether an elevated RHR is independently associated with cognitive decline or whether underlying cardiovascular diseases explain this link.
This is significant because an elevated RHR is associated with an increased risk of several cardiovascular diseases, such asischemic heart disease, atrial fibrillation, heart failure, and stroke. These diseases are also known risk factors for dementia.
MNT also spoke with Dr. Karen Harrison Dening, head of research and publications at Dementia UK, who corroborated the study’s findings:
“This study reiterates the link between cardiovascular health and brain health; what is good for the heart is good for the brain.”
“Increasing supplies of oxygen to the brain through physical exercise and giving the brain enough nutrients by eating health[y] foods, including fruits and vegetables, and reducing alcohol intake are ways to mitigate the risk of dementia, particularly vascular dementia,” Dr. Dening explained.
“It’s important that these lifestyle factors are started as early as possible in order to receive the most benefits.”