Impaired Lung Function Linked to Higher Risk of Dementia, Mild Cognitive Decline Later in Life

Middle-aged adults with impaired lung function, such as people with sarcoidosis, are at higher risk of dementia and mild cognitive impairment, according to a long-term follow-up study.

The study, “Impaired Lung Function, Lung Disease and Risk of Incident Dementia” was published in the American Journal of Respiratory and Critical Care Medicine.

Growing evidence suggests that impaired lung function, like that in diseases such as sarcoidosis or idiopathic pulmonary fibrosis, may increase the risk for dementia and cognitive decline later in life.

“Preventing dementia is a public health priority, and previous studies have suggested that poor lung health, which is often preventable, may be linked to a greater risk of developing dementia,” Pamela L. Lutsey, MD, PhD, epidemiologist at the University of Minnesota’s School of Public Health and study lead author, said in a press release. “In this study, we looked at the long-term association between poor lung function and the risk of developing dementia, using high-quality measures.”

The research team analyzed data from 14,184 participants (average age 54) in the Atherosclerosis Risk in Communities (ARIC) study, an epidemiological study conducted in four U.S. communities.

Participants performed a lung test, called spirometry, and were asked about their lung health at the beginning of the study. They were classified into four groups, according to their lung test results: normal, respiratory symptoms with normal spirometric results, restrictive impairment, and chronic obstructive pulmonary disease (COPD).

Patients were followed for 23 years on average, during which they were evaluated for dementia and cognitive impairment. During the follow-up period, there were 1,407 diagnoses of dementia.

Results showed that participants with a restrictive lung disease (such as sarcoidosis) or an obstructive lung disease had a higher risk of dementia or mild cognitive impairment — 58% and 33%, respectively — compared to those without disease or respiratory symptoms.

Patients with lower scores in two lung function tests — forced vital capacity (FVC; a measure of lung capacity) and forced expiratory volume in one second (FEV1; a measure of how much air can be exhaled in one second after a deep inhaled breath) — also had a higher risk of dementia. The increased risk was seen in both smokers and nonsmokers.

Researchers hypothesized that the low-oxygen environment that characterizes lung disease may promote inflammation and damage to the brain’s blood vessels.

Although preliminary, these findings suggest that “policy and public health efforts to reduce smoking and improve air quality may have the added benefit of preventing the development of dementia and [mild cognitive impairment],” the researchers said.

“Preventing lung disease is inherently important,” Lutsey said. “If other studies confirm our study’s findings, both individuals and policymakers will have an added incentive to make changes that protect lung health, as doing so may also prevent dementia.”