MEDICAL MATTERS:Being overweight may not be as bad for heart health as originally thought
MOST OF us are pretty up to date on the dos and don'ts of maintaining a healthy heart. Smoking, high blood pressure, obesity, physical inactivity and poor diet are the principal risk factors; diabetes, a family history of heart attack at an early age and recent menopause are more specific risks for certain people.
Interestingly, however, over half of those who develop cardiovascular disease do so without having even one of these conventional risk factors. And now comes evidence that being overweight may not be as bad for heart health as we thought.
Earlier this month, a report in the Archives of Internal Medicinecompared a group of people with a "healthy" weight to another group who were either overweight or obese.
The results suggest that half of overweight people and one-third of obese people are "healthy" as defined by cholesterol, blood pressure and other risk markers for heart disease.
Despite being overweight for their height, many overweight and obese adults have healthy levels of "good" cholesterol, blood sugar and blood pressure.
Remarkably, almost one in four slim people (as defined by body mass index - BMI) were found to have two cardiac risk factors, placing them at theoretical risk of having a heart attack or a stroke.
The research suggests that a significant number of overweight people are healthier than measurements such as BMI indicate; similarly, a percentage of those considered to be of normal weight are not as healthy as they may have thought.
So have we been barking up the wrong tree on weight and cardiovascular disease? Not really, although it now seems as if BMI may be something of a blunt instrument with which to measure risk for certain people.
There is a growing body of opinion advocating the use of waist circumference as a better arbiter of cardiac risk. Certainly for men, excessive abdominal girth is a reliable warning sign of future heart disease and diabetes.
Meanwhile, many readers will be familiar with the key role played by aspirin in preventing a second or subsequent heart attack, stroke or mini stroke. However, extensive research has shown that aspirin offers only a 19 per cent reduction for further cardiovascular events, failing to offer protection for one in eight people taking the drug.
The reason for this (and indeed the explanation as to why many drugs work better in some people and not so well in others) is because humans differ greatly. Aspirin works by preventing platelets in the blood sticking together; however, about one in 20 people have what is termed aspirin resistance, in which the platelets carry on as if there was no aspirin circulating in the body.
While there is clearly a role for identifying patients with this phenomenon, there is, as yet, no standard laboratory measurement for aspirin resistance. Nor is there a specific treatment for it, notwithstanding the availability of more potent anti-platelet drugs.
High levels of homocysteine have been linked with an increased risk of heart attack and stroke. Homocysteine is an amino acid that occurs naturally in the body. Normal levels in the blood vary between 5 and 15 micro moles/litre. High levels affect the ability of blood vessels to relax as well as causing inflammation of their lining.
While folic acid lowers homocysteine levels there are no results as yet from medical trials in which folic acid is given to people with high blood levels of homocysteine. There is evidence that folic acid improves blood vessel function in people with coronary artery disease and elevated homocysteine.
But perhaps of most interest to those of us with existing heart disease is a report in the Journal of the American Medical Association(JAMA) saying it was fitness levels that were the strongest predictors of future mortality. Adults followed up over 12 years were four times as likely to die if they had the lowest level of fitness compared with those who were able to complete a treadmill test without difficulty, and thus prove they were fit.
While losing excess weight remains a reasonable goal to reduce our risk of heart disease, those who have genuine difficulty shedding the pounds should work on their fitness levels in the knowledge that being fit but overweight can make a real difference to your health.
• Dr Houston is pleased to hear from readers at mhouston@irish-times.ie but regrets he is unable to respond to individual medical queries
