Scientists have found a way to predict the time of a person's death using a simple test

Scientists can now predict when you will die with a simple test. A simple brain scan at age 40 can reveal how long you have left to live, depending on how quickly your body ages.

Researchers at Duke University have found that magnetic resonance imaging of the brain in midlife can accurately determine the pace of a person's biological aging, helping doctors predict the onset of a number of diseases, including Alzheimer's.

Biological ageing is how quickly your body ages compared to your actual age, which can affect your health and how long you live, the Daily Mail explains.

In this study, researchers linked faster aging to physical changes in the brain that are commonly seen in older people, especially those experiencing cognitive decline.

Scientists have developed a tool called DunedinPACN, which takes a single scan and calculates a patient's "ageing rate" by analysing factors such as surface area, grey matter volume and the size of certain brain regions such as the hippocampus.

The researchers tested their new tool on brain scans of 860 people who participated in the study. The results showed that people who believed they were aging at the fastest rate were 18% more likely to be diagnosed with a chronic disease in the next few years. What's more, these "rapidly aging" people were 40% more likely to die during that period than those who aged more slowly.

Ahmad Hariri, a professor of psychology and neuroscience at Duke University, comments: "What's really cool about this is that we've captured how quickly people age using data collected in midlife, and that helps us predict dementia diagnosis in people much older."

The researchers found that people whose brain scans showed faster aging performed worse on tests of memory and thinking and had more shrinkage in the hippocampus, a key region linked to memory.

A smaller hippocampus volume was linked to a faster decline in cognitive ability, while a larger volume of ventricles (fluid-filled spaces in the brain) was linked to poorer health after middle age, the Daily Mail reports. Older people were also more likely to develop health problems such as frailty, heart attacks, lung disease or strokes later in life.

"How we age as we get older has nothing to do with how many times we've orbited the Sun," says Professor Hariri.

The study's author added that several computer algorithms have been created that serve as so-called "aging clocks," but these programs are typically based on data collected from people of all ages at a particular point in their lives.

The new study, published in the journal Nature Aging, focused on participants aged 45, allowing for greater homogeneity of results.

Software called FreeSurfer was used to process the brain scans and measure 315 different brain characteristics, including the thickness of the cortex, the outer layer of the brain. Thinner areas of the cortex may indicate faster aging or wear and tear. "The connection between brain aging and body aging is quite clear," Hariri added.

The professor stressed that the link between the rate of ageing and dementia was as strong in the study as it was across racial and economic backgrounds. Specifically, the study included low-income and non-white people living everywhere from Latin America to the UK.

"It seems to reflect what is reflected in each person's brain," Hariri said.

MRI scans also measured factors such as the gray-to-white matter ratio, which compares how bright gray matter appears compared to white matter (the brain's wires that connect different areas). Changes in this ratio can indicate differences in the health of brain tissue, such as how well the brain functions as we age.

The researchers noted that the size of the human hippocampus can also decrease with age or as a result of diseases such as Alzheimer's. Thus, a smaller hippocampus may indicate faster aging or a higher risk of dementia, especially in people in their early 40s, the Daily Mail notes.

Meanwhile, the ventricles, the fluid-filled spaces in the brain that help cushion it, often become larger as the brain tissue around them shrinks - another sign of progressive aging or brain health problems.

The team then looked at brain scans of 624 people aged 52 to 89 who were taking part in the North American Alzheimer's Risk Study. The researchers found that those who aged the fastest were 60 percent more likely to develop dementia in later life. Those who aged the fastest also began to suffer from memory and thinking problems earlier than those who aged more slowly.

These people's brains looked younger and healthier than expected, like a 30-year-old's brain in a 45-year-old's body. They had thicker cerebral cortices or larger hippocampi, and they showed fewer signs of wear and tear. They were also less likely to develop chronic diseases, meaning they tended to live longer than those who aged rapidly.

When the team saw the results, "our jaws just dropped," Professor Hariri admitted.