Kaiser Permanente researchers reviewed the medical records of 30,067 type 2 diabetes patients who had their HDL measured twice, six to 24 months apart, in 2001 to 2006. The researchers looked at whether the patients had subsequently been hospitalized for heart disease or stroke.
They compared the hospitalization risk for people whose HDL levels rose or fell between the two measurements with those whose HDL levels remained fairly stable.
Each 5-mg/dL rise in HDL cholesterol was associated with a 4% reduction in the risk of hospitalization for heart disease and stroke. But a drop in HDL of at least 6.5 mg/dL was linked to an 11% greater risk of hospitalization. This suggests "that the prevention of a HDL cholesterol decrease might be at least as important as increasing the HDL cholesterol level," the researchers write.
Half of all people with type 2 diabetes have low HDL levels, defined as below 50 mg/dlL for women and below 40 mg/dL for men, according to the researchers. The National Cholesterol Education Program, a project of the National Heart, Lung, and Blood Institute, regards HDL below 40 mg/dL as a risk factor for heart disease and stroke.
Still, research to date has not clearly shown that increasing HDL cholesterol levels will reduce the risk of heart attacks and strokes, the Kaiser Permanente researchers say, "perhaps because safe and effective agents that substantially increase the HDL cholesterol level remain elusive."
One limitation of the study is that the researchers did not have information on how patients raised their HDL, says co-researcher Suma Vupputuri, PhD, an investigator for the Kaiser Permanente Health Research Center in Atlanta.
Lifestyle changes, namely quitting smoking, increasing exercise, and losing weight, can raise HDL. But separate from their effect on HDL levels, they’re known to lower the risk of cardiovascular disease. So it’s not known whether the increase in HDL itself, or the steps patients took to get there, deserves credit for their lower risk of hospitalization.