As the human brain ages, its structure changes. A person’s ‘brain age’ can be predicted by a computer model. This method uses MRI-based machine learning to compare an individual’s neuroanatomy with a large reference set of healthy brains.
If you subtract brain age from a person’s chronological age, you can calculate their brain-predicted age difference (brain-PAD).
Studies have found that brain-PAD can predict the 8-year mortality of 70-year-oldsTrusted Source and indicate risk for multiple conditions, including dementia, multiple sclerosisTrusted Source, and depression.
Studying how brain age interacts with other physiological health measures and health outcomes could improve our understanding of the aging process.
In a new study, researchers examined how brain-PAD relates to various health outcomes over the lifespan.
They found that brain PAD is linked to cardiovascular risk and neurodegeneration. They noted that their findings might be useful for understanding patient prognoses.
The findings were recently published in The Lancet Healthy LongevityTrusted Source.
The link between brain and heart health
For the study, the researchers included data from 456 individuals who were born in the same week of 1946 in Britain. Each person underwent 24 different assessments since birth on various factors, including:
childhood cognitive ability
adult socioeconomic position
cardiovascular measures (i.e., blood pressure, smoking status, and diabetes history at ages 36 and 69)
polygenic risk score (genetic risk for various diseases)
MRI brain scan between 2015 and 2018
While participants were an average of 70.7 years old at the time of the study, their average brain-predicted age was 67.9 years. Female brains were an average of 5.4 years younger than male brains after adjusting for chronological age.
The researchers found that brain age was significantly linked to higher cardiovascular risk, poorer cognitive performance, and a smaller brain volume.
They also found that an older brain age was linked to higher levels of neurofilament light protein (NfL). While NfL levels increase with age in healthy individuals, they are also linked to neural damage.
Brain-PAD was further linked to future hippocampal atrophy, an early characteristic of Alzheimer’s disease. However, the researchers found no link between brain-PAD and various biomarkers for Alzheimer’s disease.
The researchers also reported no significant link between brain-PAD and childhood cognitive performance, education level, or socioeconomic status.
Overall, they reported that the 12 metrics accounted for in their study could explain 33% of the variance in brain-PAD.
Oxygen: How the heart affects the brain
When asked what might explain the relationship between cardiovascular health and aging in the brain, Dr. Aaron Wagen, clinical research fellow at University College London, one of the study’s authors, told Medical News Today:
“The brain is the most energy demanding organ in the body, and thus requires a constant supply of oxygen.”
“Any damage to the vascular system (e.g., heart, blood vessels) that impacts the level of oxygenated blood supplied to the brain will have a negative impact on brain health, potentially resulting in cerebral small vessel disease, white matter lesions, and brain atrophy. These brain changes can happen as part of normal aging. However, poor heart health could mean they happen earlier than expected.”
— Dr. Aaron Wagen
Dr. Lee A. Baugh, an associate professor of neuroscience at the University of South Dakota, who was not involved in the study, also told MNT that cardiovascular risk factors, such as blood pressure and smoking status, have already been linked to premature brain aging.
“The precise mechanisms by which cardiovascular health and aging in the brain are linked are likely incredibly complicated, but will certainly have to do with things such blood flow delivery to the brain, cardiac hemodynamics, and arterial stiffness,” Dr. Baugh said.
“I think the more exciting question is whether the composite measurement of cardiovascular health used in the present study is providing unique information above and beyond what these individual factors provide, and the answer to that question really requires further study. That being said, it is great to see these types of connections being made between brain and body health,” he added.
Male vs. female brain
MNT also asked the researchers what might explain the differences in brain age between men and women.
“In this cohort, we have seen that females outperform males in several measures, including cognitive tests. The younger brain predicted age seen in women may reflect this, [alongside] in general the differences in life expectancy in the U.K. population where women live longer than men. The mechanisms underlying this require further study, but cardiovascular health might contribute,” Dr. Wagen said.
The researchers concluded that their findings would enable further exploration into brain age and predict future decline.
As for the study’s limitations, Dr. Wagen noted that his study was conducted mainly on white British participants, and thus may not apply to other demographics.
Dr. Baugh pointed out that due to how some of the statistical analyses were performed, there is an increased likelihood of false positive results or findings that do not exist. He noted that future research should examine the relationships with more “conservative statistical approaches.”
He added that there are now multiple methods to calculate brain age other than that used in the study and that further research is needed to understand which is optimal.