People with obstructive lung disease are at higher risk for mental impairments such as memory loss, recent research has found. Obstructive lung diseases are forms of airway obstruction that include asthma, bronchitis and chronic obstructive pulmonary disease (COPD).
Earlier work suggests that people with obstructive lung disease often experience “global cognitive impairments,” that is, problems with a range of mental processes. Although 12 percent to 88 percent of patients may be affected, according to different estimates, previous studies have looked only at global cognitive function.
This particular study aimed to discover which specific cognitive functions are affected in people with obstructive lung disease. It found that there may be a pattern of specific cognitive dysfunctions.
Fiona Cleutjens, Ph.D., and colleagues from the Center of Expertise for Chronic Organ Failure in The Netherlands used figures from the UK Biobank Resource, which contains medical information on more than 500,000 Scottish, English, and Welsh people aged 40 to 69 years.
From this resource, the team identified 5,764 men and women with obstructive lung disease and 37,275 comparable people without lung disease. All completed several tests to examine cognitive performance and lung function.
Analysis of the test results showed that people with obstructive lung disease performed significantly worse on memory tests and reaction time, “an indirect indication of the cognitive processing speed.” They also scored worse on matching-pairs tests, which “reflect the capacity to understand and remember the spatial relation among objects.”
This effect seemed to be dose-responsive for some measures, with more impairment at higher degrees of airflow limitation. Participants with the least severe obstructive lung disease had significantly better scores than those in the most impaired group.
The researchers say this suggests that people with obstructive lung disease “are more likely to experience domain-specific cognitive impairment, particularly in memory and information processing.” Details of the study were presented at the European Respiratory Society Annual Congress in September 2013.
Cleutjens said, “We know that obstructive lung disease can often exist alongside other conditions and our new study has found evidence that obstructive lung disease is linked with problems with memory and information processing.
“This can be very debilitating, especially for someone who is already dealing with the symptoms of lung disease. Healthcare professionals need to be aware of the possible impact of cognitive impairment in the self-management, clinical management and pulmonary rehabilitation of obstructive lung disease patients.
“Cognitive impairment may have negative consequences for daily functioning, health status, and treatment adherence,” Cleutjens added. She recommends routinely screening obstructive lung disease patients for cognitive problems.
However, she pointed out that the battery of tests used in this study may not be clinically feasible at a regular appointment. So a simple screening questionnaire would be a good first step, she said, after which any patients showing problems could be given further tests to determine which aspects of cognition are impaired. Alternatively, physicians may decide to selectively test only those patients who report cognitive difficulties or who have other risk factors for cognitive impairment, such as vascular problems.
Co-researcher Sally J. Singh, Ph.D., of University Hospitals of Leicester, U.K., pointed out that the observational results in this study can’t show causality or determine the direction of the link.
The participants’ medications may also affect their test performance, she added. For example, anticholinergic drugs are often given for obstructive lung disease, and these are associated with memory loss in some people.
People with obstructive lung disease have increased hemoglobin in the blood, together with “hyperviscosity” of the blood, which impedes blood flow to the body and brain.
Hypoxic injury, or loss of blood flow to the brain, may also underlie the association with brain function. The brain needs a continuous supply of oxygen, and if the supply is interrupted, brain functioning is disturbed immediately and can result in irreversible damage. So patients with obstructive lung disease are at increased risk of injury to brain cells.
Brain cells may also be damaged through other conditions the patient may have which adversely affect the brain, such as vascular disease, or by smoking. Some obstructive lung disease treatments, as well as treatments for associated conditions, could therefore benefit brain function, but the evidence for this secondary benefit of treatment is currently limited.
Cleutjens, F. et al. Cognitive functioning in OLD: results from the UK Biobank. Presented at the European Respiratory Society Annual Congress held in Barcelona, Spain, from 7 September to 11 September 2013.