A study shows that nearly half of all Americans have Alzheimer’s disease and that this increases the risk of developing the disease.
Seniors with untreated high blood pressure are about one-third more likely to be diagnosed with Alzheimer’s
About 120 million people have high blood pressure, caused by a range of factors including poor diet, lack of exercise, smoking, genetics and age. But only about a quarter of them have it under control.
High blood pressure can be difficult to treat, simply because many people do not know they have it, as it often has no symptoms. It has been nicknamed the ‘silent killer’.
It damages blood vessels, restricting blood flow and oxygen supply to the brain and making it unable to clear toxic protein deposits that are a hallmark of Alzheimer’s.
High blood pressure causes blood vessels to constrict. The heart has to work harder to pump more blood, but constricted blood vessels prevent oxygen from reaching the brain, which likely supports the link to Alzheimer’s.
The benefits of maintaining healthy blood pressure (aim for 120/80) for heart health are well known and well documented.
But the condition’s link to Alzheimer’s is less clear. Now, an NIH-backed study is trying to shed more light on the connection.
Researchers from the University of New South Wales in Australia combined data from 14 unique studies involving 31,250 people from several countries, including Australia, Brazil, China, France, Germany, Greece, Italy, Japan, Korea, Nigeria, Congo, Spain, Sweden and the United States.
The average age of the people who participated in the studies was 72 years. However, the researchers took into account the risk of Alzheimer’s in adults aged 60 and over.
Each person in the studies was followed for an average of four years, and 1,415 of them developed Alzheimer’s disease.
The researchers recorded the person’s blood pressure, whether they had hypertension, and whether they were taking medications to treat the blood pressure.
They found that 9 percent had untreated high blood pressure, 51 percent were taking medication for high blood pressure, 36 percent did not have high blood pressure, and 4 percent were classified as uncertain.
After taking into account variables such as the person’s age, gender and education level, the researchers found that people with untreated high blood pressure were 36 percent more likely to develop Alzheimer’s than people with normal blood pressure.
Adults aged 60 and older with untreated high blood pressure had a 42 percent higher risk of Alzheimer’s compared with people who had high blood pressure but were taking medication.
Dr Matthew Lennon, a dementia researcher at the University of New South Wales and an author of the paper, said: ‘Our meta-analysis, which included people from around the world, showed that taking blood pressure medications was linked to a lower risk of developing Alzheimer’s disease in later life.
“These results suggest that treating high blood pressure as a person ages remains a critical factor in reducing the risk of Alzheimer’s disease.”
The report was published in the journal Neurologythe medical journal of the American Academy of Neurology.
High blood pressure and heart disease go hand in hand.
There are several factors that can contribute to high blood pressure, including genes, age, diet, level of physical activity, obesity, smoking habits, and stress.
How exactly high blood pressure develops remains a question among doctors and researchers. It appears to develop through a few different processes.
One way this happens is when the body takes in too much salt from an unhealthy diet, which increases the blood volume in the body.
Another way is when the body’s system that regulates blood pressure (the renin-angiotensin-aldosterone system, or RAAS) isn’t working properly.
In addition, the nervous system can also contribute to overactivity. All of these conditions cause blood vessels to constrict, which forces the heart to work harder to pump blood.
When a person’s blood pressure is consistently 130/80 mmHg or higher, a doctor will typically diagnose hypertension.
Blood pressure readings show two numbers, representing diastolic and systolic pressure. Diastolic refers to the force of blood in the arteries when the heart is relaxed between beats. It is the number at the bottom.
The systolic pressure is the number at the top and measures the pressure in the arteries during a heartbeat.
This graph shows the prevalence of high blood pressure among U.S. adults by age and sex. (Source: Heart Disease and Stroke Statistics–2020 Update: A Report From the American Heart Association)
The link between high blood pressure and Alzheimer’s disease is still a topic of much scientific research, but scientists have already discovered some important connections.
In addition to damaged blood vessels that keep oxygen out of the brain, hypertension is a major risk factor for strokes caused by a lack of oxygen in the brain. This degree of oxygen deprivation, particularly in the left hemisphere, can lead to vascular dementia.
High blood pressure also causes an inflammatory response throughout the body, which causes oxidative stress.
This is believed to play a role in the progression of Alzheimer’s by damaging brain cells and accelerating the build-up of harmful amyloid plaques and tau tangles, which are common in brains affected by the disease.
The researchers cautioned that their findings do not prove that high blood pressure causes Alzheimer’s, only that there is a link. They also noted that too few people are taking the necessary steps to reduce their risk of future neurological disorders.
Dr Lennon said: ‘High blood pressure is a major cause of stroke and cerebrovascular disease. However, blood pressure can be controlled with medication, reducing the risk of these diseases.’