Taking a statin to lower LDL or ‘bad’ cholesterol is of limited use in warding off the risk of heart attacks and cardiovascular disease unless low levels of HDL or ‘good’ cholesterol are also addressed, researchers from Tufts Medical Center in Boston, US have found.

The research team led by Dr Richard Karas, professor of medicine at Tufts University School of Medicine, examined the relationship between HDL cholesterol (HDL-C) and cardiovascular disease (CVD) risk in patients taking statins. While statin therapy does reduce CVD risk, the incidence of CVD events in statin-treated patients remains unacceptably high, they observed.

Karas et al identified 20 eligible randomised controlled trials of statins, with 543,210 person-years of follow-up and a total of 7,838 myocardial infarctions. The analysis revealed a significant inverse association between HDL-C and the risk of myocardial infarction.

After adjustment for on-treatment LDL cholesterol (LDL-C) and age, every 10mg/dL reduction in HDL-C was associated with 7.6 and 7.8 more MIs per 1,000 person-years respectively in patients taking statins and in non-statin controls. At the same time, statin treatment cut the risk of MIs by a median of 4.4 per 1,000 person-years.

“While statins overall prevent four heart attacks per 1,000 patient-years, these new findings demonstrate that a 10-point higher HDL-C level could save an additional eight heart attacks per 1,000 patient-years, which indicates that, even if patients are on a statin, if they have low HDL-C, they may need more than just statins to significantly reduce their risks,” Karas commented.

“We believe most clinicians will be surprised to see the magnitude of the effect of low HDL-C on heart attack risk and how little statins impact the risk associated with low HDL-C,” he said.

The analysis also explored the association between HDL-C and cardiovascular disease, as well as coronary heart disease death, CVD death and all-cause death. In all these cases, the findings indicated that risk increased as the levels of HDL-C fell, and there were minimal differences between patients who were or were not taking statins.

Data from the Tufts Medical Center study were released at the American Heart Association Scientific Sessions 2009 in Orlando, Florida.