Now is the time to take action against Alzheimer's, especially if a close relative has the disease, writes Padraig O'Morain
'Prevention is cheap, intervening is expensive," says Dr Dermot Power. He is talking about the emerging link between high blood pressure in mid-life and Alzheimer's disease in later life.
The price we pay for failing to intervene in our own health by doing sensible, inexpensive things, is just too high if that failure leads to a condition such as Alzheimer's later on, he believes.
As a consultant geriatrician at the Mater Hospital and St Mary's (Phoenix Park), he sees many patients with Alzheimer's.
Dr Power believes he would see fewer if people took better care of their health and kept down their stress levels and blood pressure in mid-life.
The link between high mid-life blood pressure and Alzheimer's was first reported in the British Medical Journal in 2001.
A 21-year Finnish study of 1,500 individuals found that "people with raised blood pressure had a significantly higher risk of Alzheimer's disease in later life even after adjusting for age, education, smokers, drinkers etc.," he says.
"Compared to people with a normal blood pressure the people with raised blood pressure were at 2.3 times greater risk of developing Alzheimer's."
That's a pretty startling figure but he cautions "the relationship between blood pressure and dementing illness is not in quite the straight line suggested by that. When you develop a florid dementia your blood pressure tends to fall anyway." ("Florid" refers to a stage which can include hallucinations, agitation and incoherent speech.)
Nevertheless, the trend has emerged again in follow-up studies. A US study "found that the relationship is particularly strong in men with mid-life blood pressure. It is particularly strong if there is a first-degree relative [parent, sibling or offspring] with Alzheimer's disease."
A person's genetic inheritance appears to increase the possibility that a particular occurrence such as high blood pressure will lead to Alzheimer's, he says.
But he is anxious not to move too far beyond the research in the conclusions he draws.
"While it has been shown that high blood pressure in mid-life predicts dementia it hasn't been shown that treating it prevents dementia," he says. Nevertheless, "when I see a patient with Alzheimer's disease I would often talk to the family about their parent and say look there's increasing evidence there's a hereditary component. You should go to the GP and get it checked out."
And while it hasn't yet been shown that reducing blood pressure reduces the likelihood of dementia, there are still powerful incentives for getting your blood pressure down: "For every 10mm reduction in systolic blood pressure you get a 40 per cent reduction in the risk of stroke," he says. "People with the lowest blood pressure have the fewest number of strokes." The pressure when your heart is pumping out blood is systolic blood pressure and is higher than the pressure - called diastolic blood pressure - when it is relaxing and refilling.
So why don't we pay more attention to our blood pressure if the consequences of not doing so can be so horrendous?
"The difficulty is people don't feel unwell with high blood pressure unless it's extremely high," he says.
Worse, the drugs used to treat the condition "can make them feel unwell". Even people taking the medication "after a year or so will say what am I taking this for?" and may stop.
Other ways of keeping blood pressure down include exercising and reducing the amount of salt in the diet, "the common sense type of stuff", he says. He points out, though, that "for some people drugs are the only thing".
Social contact can also keep people alive and healthier for longer. Studies in the US suggest that people who live to be a hundred years old "commonly seem to have a big social network of friends and family".
Another factor which can lead to people ignoring high blood pressure is the mistaken belief that the worst that can happen is a heart attack which will kill you quickly.
"People need to realise that blood pressure won't necessarily kill you," he warns. "You can live, disabled cognitively, physically and emotionally."
It's one thing to be killed by a stroke. It's quite another "to survive unable to speak, unable to get out of bed". Such tragedies occur every day, he says.
A good time to start living a healthy lifestyle in order to keep blood pressure at a healthy level, is now. People in their 40s should be having their blood pressure checked.
"People think they can defer health intervention until later in life - but you are laying the groundwork now," he says.