How soon should we start protecting our brains from developing dementia? And when does it become too late to even try?

High blood pressure is hard on the brain. It causes strokes that can kill you or leave you demented.

It can cause mini-strokes that might not kill you but will bring on rapid cognitive decline.

Then there’s subcortical vascular dementia in which the small blood vessels deep within the brain are damaged.

More young people at risk

Last year, an international study found that people with high blood pressure diagnosed before the age of 55 had smaller brains compared to people who had normal blood pressure.

They were also more at risk of developing dementia.

This wasn’t surprising: An association between hypertension in mid-life and dementia in later life is well documented – and research into dementia risk has largely focused on people aged over 40.

But the researchers were keen to see how hypertension affected the brains of younger people. For good reason: High blood pressure is becoming more common in young adults.

The researchers reported that people diagnosed with high blood pressure between ages 35 and 44 were 61 per cent more likely to develop dementia during the study’s follow-up period eight to 10 years later, compared to individuals who had normal blood pressure during the same years.

They also found that people diagnosed with hypertension before the age of 35 had the greatest amount of brain shrinkage.

Dr Mingguang He, senior author of the study and professor of ophthalmic epidemiology at the University of Melbourne, said that while “the association among hypertension, brain health and dementia in later life has been well established, it was unknown how age at onset of hypertension may affect this association”.

Bottom line: Efforts to control blood pressure in young adulthood might prevent dementia in later life.

As we reported in January, dementia cases are predicted to triple by 2050 – hence, we need all the preventative measures we can get.

For more about this research, see here.

But what about later life?

When does it become too late to protect your brain?

A heartening new study – involving participants with an average age of 69 and a history of blood pressure – has found “the strongest evidence to date that lowering blood pressure in later life can cut the risk of dementia”.

The study was led by Dr Ruth Peters, associate professor at UNSW Sydney. She is also program lead for dementia in The George Institute’s global brain health initiative.

Although many studies have investigated the health benefits of lowering  blood pressure, these have largely been focused on heart health.

“Most trials were stopped early because of the significant impact of blood pressure lowering on cardiovascular events, which tend to occur earlier than signs of dementia,” Dr Peters said.

But some major studies that looked at brain health were also stopped early.

According to a Harvard article, the high-profile 2019 randomised clinical trial known as the SPRINT-MIND study was “designed to measure the effects of lowering high blood pressure on dementia and/or mild cognitive impairment”.

The Harvard Medical School article said that this study was so successful at reducing the risk of mild cognitive impairment by lowering high blood pressure “that it ended early, because the data and safety monitoring board felt that it was unethical to continue the control group”.

This led to the possibly premature conclusion “that treating systolic blood pressure to below 120 mmHg did not reduce risk of dementia”.

The new study

In the five original studies, participants – a total of 28,008 people with an average age of 69 and a history of high blood pressure from 20 countries – were given blood pressure medications or a placebo.

The average follow-up was about four years.

The meta-analysis found “there was a significant effect of treatment in lowering the odds of dementia associated with a sustained reduction in blood pressure in this older population”.

Dr Peters said the results “imply a broadly linear relationship between blood pressure reduction and lower risk of dementia, regardless of which type of treatment was used”.

Dr Peters said no evidence of harm from treatment was identified.