Heart changes between early adulthood and middle age can cause cognitive decline

By Georgia Lambert via SWNS

Changes in the structure of a person's heart between early adulthood and middle age can cause a decline in thinking and memory skills, according to a new study.

Subtle changes in the structure and diastolic function of the heart are associated with a person’s cognitive decline in brain health later in life, say scientists.

Study author Dr. Laure Rouch from the University of California, said: “Cardiovascular risk factors such as high blood pressure, high cholesterol and diabetes have been associated with an increased risk for cognitive impairment, but much less is known about heart structure and function and the risks for cognition.

“We followed young adults for 25 years into middle age and found declines in thinking and memory skills independent of these other risk factors.

"Our findings are of critical importance in the context of identifying potential early markers in the heart of increased risk for later-life cognitive decline.

“Such abnormalities are common and often underdiagnosed as they do not produce any obvious symptoms.”

The team looked at more than 2,600 people with an average age of 30.

The participants then underwent non-invasive echocardiograms and ultrasound scans of their hearts - both at the start of the study and again 20 and 25 years later.

The team then used the images to measure the weight of the left ventricle, one of the four chambers of the heart and the volume of the blood that filled the left ventricle when pumping.

They also used the images to test how well the participants’ left ventricles pump blood to the body, specifically focusing on the percentage of blood pumped out of the heart.

Over the 25 years, the scientists observed an average increase of 0.27 grams per square meter (g/m2) per year, in the weight of the left ventricle.

They went on to find an average weight of 81 g/m2 in the first year, and 86 g/m2 in the last year.

The scientists also confirmed that there was an average increase in the left atrial volume of 0.42 millilitres of blood per square metre (mL/m2), with an averaged volume of 16 mL/m2 in the first year, compared to 26 mL/m2 in the last year.

In the last year of the study, the participants were asked to complete six cognitive tests to measure their thinking and memory skills including, global cognition, processing speed, executive function, delayed verbal memory, and verbal fluency.

These tests included tasks such as recalling words from a list ten minutes after looking and memorizing them, as well as substituting symbols for numbers using a key at the top of the test’s page.

After adjusting for factors like age, sex and education, the researchers found that a greater than average increase from early to middle adulthood in the weight of a person’s left ventricle was associated with “lower midlife cognition” on most of the tests.

As well as simple memory tasks, the researchers asked the participants to take part in a common dementia exam - completing tasks like drawing lines connecting alternating letters and numbers, and repeating words after doing activities.

The scores ranged from zero to 30 with 26 and higher, representing normal cognition, and the team found that the participants with a greater than average midlife increase in left ventricle weight, scored an average of 22.7.

While, the participants who hadn’t experienced a greater than average increase in weight had an average score of 24.

The researchers also found a greater than average increase from early to middle adulthood in left atrial volume which has been associated with lower midlife global cognition.

When the researchers observed a greater-than-average decrease in the percentage of blood pumped out of the left ventricle, the incidence was not associated with cognition.

Dr. Rouch said: “What is interesting is that our results were similar after adjusting for cardiovascular risk factors such as high blood pressure, diabetes, smoking and obesity.

“As early as young adulthood, even before the occurrence of cardiovascular disease, there may be heart abnormalities that could be risk markers for lower thinking and memory skills in middle age.

“In the future, a single echocardiogram may help identify people at higher risk of cognitive impairment.”

Dr. Rouch says that future research would determine whether interventions to improve the structure and function of the heart could benefit brain health.

She added: “The question of whether altered cardiac structure and function could be a risk factor for cognitive impairment has major public health implications and could reveal another important heart-brain connection.”

The study was published in the online issue of Neurology - the medical journal of the American Academy of Neurology.