Reduced Lung Capacity Accelerates With Diabetes

People who have diabetes encounter a faster loss of lung capacity than those who do not have diabetes, a finding that may have implications for the potential use of inhaled insulin, according to a study appearing in the April issue of Diabetes Care.

The April issue also contains a consensus statement from the American Diabetes Association and American College of Cardiology Foundation emphasizing the need for more aggressive goals in controlling lipids to reduce cardiometabolic risk. In particular, the paper focuses for the first time on the need to test for and treat high levels of a protein called apolipoprotein B (ApoB), a more direct measure of the number of LDL particles that lead to plaques that cause heart disease (atherosclerosis). This is based on evidence that levels of ApoB are a better indicator of heart disease risk than total cholesterol or LDL ("bad cholesterol").

Reduced Lung Capacity in People With Diabetes

The lung research, part of a larger investigation known as the Atherosclerosis Risk in Communities (ARIC) study, confirmed previous suggestions that the lung is a target organ for diabetic injury and that lung abnormalities accelerate once diabetes takes hold. Previous research by the same authors established that decreased lung capacity precedes and may predict a diagnosis of diabetes. The new study is accompanied by an editorial that concludes that diminished lung function may contribute to diabetes morbidity and mortality.

Specifically, the study found that people with type 2 diabetes experienced a more rapid decline in forced vital capacity, the measure of how well the lungs fill with air, than people who did not have diabetes. Though all people experience a decline in forced vital capacity as they age, people with diabetes appear to undergo a more rapid loss that appears before the diabetes diagnosis and accelerates after the disease sets in.

This could be because high blood sugar levels stiffen the lung tissue, or because the fat tissue in the chest and abdomen may confine the lungs more in people with diabetes, explained the researchers. They concluded the study with advice to clinicians to "pay heightened attention to pulmonary function in their patients with type 2 diabetes."

"Think of the lung as a crime victim who unwittingly abets the perpetrator to hasten the demise of the host," wrote Dr. Connie Hsia, of the University of Texas Southwestern Medical Center's Department of Internal Medicine, in an editorial accompanying the study. She suggested that the loss of pulmonary function could add to diabetic morbidity and mortality, and raised concerns about the potential use of inhaled insulin, since it may "trigger or exacerbate pulmonary dysfunction."

Recently, makers of inhaled insulin have pulled their products from the market because of poor sales or halted product investigations, though several companies continue to explore this type of insulin delivery.

"Manufacturers of inhaled insulin should find these data useful as they study potential long-term effects of their product on lung function," said Dr. Fred Brancati, one of the lead researchers on the study. "The results suggest that doctors and patients should keep an eye on the literature about diabetes and the lung down the road, since there's a stronger connection than we previously thought."

Consensus Statement Urges Greater Lipid Control

The ADA-American College of Cardiology (ACC) paper highlights a new consensus suggesting that, in people who exhibit cardiometabolic risk factors (such as insulin resistance, hypertension, overweight/obesity, or a family history of premature heart disease), a certain protein called apolipoprotein B (ApoB) may better predict the risk of heart disease than LDL cholesterol levels, long used as one measurement of good heart health. A panel of diabetes and heart experts agreed that LDL ("bad") cholesterol was still an important risk factor, but that after LDL cholesterol levels were brought under control, ApoB (a measure of the number of LDL particles in the blood that cause hardening of the arteries) should also be tested and treated to target levels in people at high risk.

The statement emphasizes the need to examine all factors for heart disease, to continue to focus on lifestyle interventions to reduce the risk for type 2 diabetes and heart disease, and to more aggressively control all lipids. The paper also urged health care providers to look at a person's lifetime risk for heart disease, rather than just at short-term risks.

Diabetes Care, published by the American Diabetes Association, is the leading peer-reviewed journal of clinical research into the nation's fifth leading cause of death by disease. Diabetes also is a leading cause of heart disease and stroke, as well as the leading cause of adult blindness, kidney failure, and non-traumatic amputations. For more information about diabetes, visit the American Diabetes Association Web site http://www.diabetes.org or call 1-800-DIABETES (1-800-342-2383).