Salt

In overweight and obese populations, controlling high blood pressure was the most effective way of reducing the added risk of heart attacks and strokes. But driving down high cholesterol and glucose levels helped too. (Ricardo DeAratanha / Los Angeles Times / October 21, 2008)

A study that culls health data for 1.8 million people over more than 57 years of research finds that controlling high blood pressure, cholesterol and glucose could halve the number of heart attacks attributable to being overweight or obese and pare the number of strokes linked to excess weight by 75%.

In populations in which being overweight or obese are widespread, the new research offers a guide to which public health policies most effectively drive down heart attacks and strokes. Published online in the Lancet on Thursday, the study was conducted by an international consortium of researchers led by Harvard University's School of Public Health.

By far, the most effective of the available interventions, the study found, is treatment of hypertension. If all cases of high blood pressure stemming from being overweight or obese were kept in check by measures such as increased physical activity, medication and dietary sodium reduction, 31% of coronary heart disease cases caused by excess weight could be averted, the authors reckoned. Eliminating hypertension could drive down the incidence of strokes linked to excess weight by 65%.

Controlling glucose was found to be the next most effective means of reducing heart disease and strokes attributable to excess weight, followed by reducing serum cholesterol.

In this massive collection of studies, being overweight was associated with a 26% increased risk of heart attack and a 13% increased risk of stroke. (This finding appeared to contradict studies suggesting that those with a body mass index between 25 and 30 bear no greater risk of heart attack or stroke than those with BMIs bellow 25.) On average, getting treatment for hypertension, high cholesterol and high glucose readings reduced an overweight person's increased likelihood of suffering a heart attack to 13% on average, and brought her risk of stroke down to that of a person of normal weight.

Among obese populations, carrying excess weight drove the risk of coronary heart disease up by 69% and of stroke by 47% on average. Controlling hypertension, high glucose and blood cholesterol in these populations would shrink those added risks to 39% for coronary heart disease and 14% for stroke.

The authors were especially keen to mine their massive accumulation of data for evidence of differences based on ethnicity, but found none.

The results may help explain why, despite growing obesity in the United States, rates of heart attack and strokes have declined somewhat in recent decades. Studies showed that aggressive hypertension and cholesterol control in the United States has brought those disease risk factors under better control among the overweight and obese than in normal-weight people. But in Asia, hypertension remains widespread, serum cholesterol is on the rise, and stroke is a common cause of death.

An optimally healthy population would maintain normal healthy weight, defined as a body mass index between 20 and 25, the researchers said. But weight-loss programs tend to yield ephemeral results, diet drugs are either ineffective or unsafe, and access to bariatric surgery is limited by its cost, they said. Amidst burgeoning obesity, they wrote, public health officials will have to use the tools they have in hand to avert "a potentially massive worldwide increase of cardiovascular disease."