The BBC's Daniel Sandford reports: "It's a major cause of both strokes and heart attacks"

It is estimated that some five million people over 65 have high blood pressure, a major risk factor for heart disease and stroke.

But a report commissioned by the Department of Health from the University of York says about half of the people who could benefit from anti-hypertension drugs are not getting them.

And it says 50% of these are not being given the right drugs or dosage.

Drug side-effect

The researchers say part of the reason is that some GPs consider hypertension to be a normal part of the ageing process.

Some also fear that elderly people with other illnesses could respond badly to the drugs.

There are also concerns about the cost implications of treating half the population aged over 65 with drugs.

But the University of York researchers say the majority of elderly people will not experience strong side-effects from taking the drugs.

Minor side effects include dizziness, headaches and rashes.

Severe effects can range from kidney disorders to palpitations, but the study says these can be avoided through careful monitoring.

Saving lives

The researchers believe diuretics, one of the most common of the anti-hypertensive drugs, are the most effective for elderly people.

Although they admit there is no agreement yet on what the best level of blood pressure is for elderly people, they say any reduction from a conservative definition of hypertension - more than 160mm Hg systolic or more than 95mm Hg diastolic - "is likely to be beneficial".

The researchers also insist that diuretics are cost-effective.

Indeed, they say they are most cost effective when targeted at elderly people and could reduce up to 40% of deaths from stroke and help many older people maintain a healthy and active lifestyle.

They point out that previous research shows doctors only have to treat 50 patients over 60 with anti-hypertensive drugs for a period of five years to prevent one stroke, compared with 168 aged under 60.

The University of York research is being published on Thursday and will be distributed to all GPs and NHS organisations.

A spokeswoman for the university said she hoped its findings would be taken forward and implemented locally.

Media campaign

Geriatrician Professor Martin Severs told the BBC's One O'Clock News that the NHS was failing elderly people with high blood pressure.

Professor Martin Severs: The system is failing the elderly

But he said the problem was complex. Research was only just filtering through and patients and carers had little knowledge about their rights and responsibilities regarding high blood pressure.

He added that it was not just up to GPs to spot and treat hypertension.

He said: "People need to take this report very seriously."