Uncontrolled high blood pressure can damage the brain’s structure and function even in young middle-aged people, a new study has claimed.

Researchers from the University of California found that brains of middle-aged people, who clinically would not be considered to have hypertension, have evidence of silent structural brain damage.

The study is the first to demonstrate that there is structural damage to the brains of adults in young middle age as a result of high blood pressure, the authors said.

The investigation found accelerated brain ageing among hypertensive and pre-hypertensive individuals in their 40s, including damage to the structural integrity of the brain’s white matter and the volume of its gray matter, suggesting that vascular brain injury “develops insidiously over the lifetime with discernible effects’’.

“The message here is really clear: People can influence their late-life brain health by knowing and treating their blood pressure at a young age, when you wouldn’t necessarily be thinking about it,” study senior author Charles DeCarli said in a statement.

Earlier studies have identified associations between elevated blood pressure and a heightened risk of brain injury and atrophy leading to reduced cognitive performance and a greater likelihood of dementia, making hypertension an important, modifiable risk factor for late-life cognitive decline.

There is evidence, the new study said, that lowering blood pressure among people in middle age and in the young elderly can help prevent late-life cognitive decline and dementia.

The study found that in hypertensive individuals, fractional anisotropy in the frontal lobes was reduced by an average of 6.5 per cent. The hypertensives also had 9 per cent less gray matter, on average, in their brains’ frontal and temporal lobes.

Hypertensive individuals’ brains were significantly less healthy than those of subjects with normal blood pressure.

For example, a typical 33-year-old hypertensive’s brain health was similar to that of the typical 40-year-old normotensive subject. So, for those 33-year-olds, high blood pressure had prematurely aged the brain by seven or so years.

The authors did not postulate a mechanism for the damage. However, they noted that high blood pressure causes arteries to stiffen, thus making the blood flowing to the brain pulse more strongly.

This stresses the blood vessels of the brain, likely making it more difficult for them to nourish brain tissue such as axons.

The study was published in the journal The Lancet Neurology.