As we live longer we’re looking more closely at what’s going on in middle age so we can try to determine how healthy we are going to be in old age.

A new study has examined blood pressure and discovered that only a small rise may predict a risk of ­dementia later on. Crucially, this rise is below the threshold commonly used to treat high blood pressure.

It would seem 50-year-olds with slightly raised blood pressure are at an increased risk of getting dementia in later life even if they don’t have other heart-related problems.

The surprising finding was that the association between blood pressure and dementia risk was seen at age 50, but not 60 or 70.

The research analysed 8,639 people, as part of the long-running Whitehall II study of more than 10,000 civil ­servants tracked since 1985.

People aged 50 with a systolic blood pressure (the higher blood pressure reading) of 130 mmHg – which is between the ideal range (90/60mmHg and 120/80mmHg) and ­considered to be on the high side (140/90mmHg) – or above, have a 45% greater risk of developing dementia.

The association between blood pressure and dementia risk was seen at age 50, but not 60 or 70 (Image: Getty)

Those taking part in the study were people who had developed dementia at an average age of 75.

Dr Jessica Abell, author and a research associate in dementia and epidemiology at University College London, said they designed the study to look in more detail at what is considered “midlife”.

She said: “Previous research has not been able to test the link between raised blood pressure and dementia directly by examining the timing in sufficient detail. In our paper we were able to examine the association at age 50, 60 and 70, and we found different patterns. This will have important implications for policy guidelines, which currently only use the generic term ‘midlife’.”

Professor Archana Singh-Manoux, honorary professor at UCL who led the research, said: “Our work confirms the detrimental effects of midlife ­hypertension for risk of dementia, as suggested by previous research.

“It also suggests that at age 50, the risk of dementia may be increased in people who have raised levels of systolic blood pressure below the threshold used to treat hypertension.”

Researchers suggested a possible reason for the link could be resulting damage from silent or mini strokes, which often have unnoticed ­symptoms, and which are linked to high blood pressure.

Dr Abell noted that the findings were from “observational, population-level research” and therefore “do not translate directly into implications for individual patients”.

Nor do they prove cause and effect. But they’re important all the same.