ICAD: Lung Function Deficiency Tied to Dementia Risk

MADRID, July 18 -- Lung function of Medicare-age patients, as measured by standard spirometry, can suggest how likely they are to develop dementia in the next five to six years, researchers reported here.

Lung capacity tests were performed with patients, all 65 or older, who were followed prospectively for more than five years before they were examined again and their dementia status was assessed, said a Seattle team.

Dementia in this study was defined as total dementia, including the dementia subtypes of Alzheimer's disease, vascular dementia, and mixed dementia.

"We observed that poor lung function is associated with an increased risk of dementia in older adults," Suzanne Craft, Ph.D., of the University of Washington reported at the International Conference on Alzheimer's Disease and Related Disorders.

Laura Frank, Ph.D., a co-author, said the investigators found a 2.8-fold increased risk of dementia among those in the lowest quartile of forced vital capacity (FVC) measurements compared with those with the high volumes. There was also a 2.5-fold increased risk of dementia in those in the lowest quartile of forced expiratory volume in one second (FEV-1) volumes.

Forced vital capacity and forced expiratory volume are standard spirometry examinations performed to test a patient's pulmonary system.

The 2,418 patients were given the lung tests in 1992 and 1993 as part of the Cardiovascular Health Cognition Study. The cohort was re-examined for evidence of dementia in 1998-99, the Seattle team said in its poster presentation.

For each liter increase in FVC and FEV-1, respectively, there was a 38% and 45% decrease risk of dementia (HR: .62 [.54-.72] and HR: .55 [.45-.66]), the investigators reported.

"Although these relationships are not causal," Dr. Frank said, "achieving and maintaining healthy lung function may reduce the risk of incident dementia in later life."

Dr. Craft added, "Our results suggest lung function may be a predictor for future risk of dementia. These findings also suggest that prevention or better treatment of lung diseases could have important additional benefits on decreasing the risk of dementia in older adults."

After adjusting for confounders, the researchers said they found that the association between FVC and dementia was modified by smoking (P=.05) and that the association between FEV-1 and dementia was modified by diabetes (P=.003) and by sex (P=.050).

"Better lung function reduced the risk of incident dementia to a greater extent among never smokers, women and for patients with Type 2 diabetes or impaired fasting glucose," Dr. Craft said.

"It is plausible that poor lung function could be related to dementia due to decreased oxygenation of brain blood vessels," commented Marilyn Albert, M.D., a professor of neurology at Johns Hopkins

However, she also said it was possible that the older patients recruited in the study failed to perform the lung tests correctly. "While these tests are not difficult to perform, patients have to be able to follow instructions correctly to get the desired results," Dr. Albert said. She said the trial results might have been skewed by a few patients not doing the tests right.

She added, however, that older individuals should work to keep their lungs clear of pollutants such as cigarette smoke and to take care of their lungs by getting vaccines to protect against influenza.