COPD is the 3rdleading cause of death in the United States. The disease kills more than 120,000 Americans each year or 1 death every 4 minutes and causes serious, long-term disability. The number of people with COPD is increasing. More than 12 million people are diagnosed with COPD and an additional 12 million likely have the disease and don’t even know it, according to the NIH.
Recent studies suggest that up to 77% of patients with both COPD and hypoxemia have some form of cognitive impairment. However, few well-designed population-based studies have examined the association between COPD and MCI (mild cognitive impairment).
In this new study Dr. Balwinder Singh, M.D, psychiatry resident at the University of North Dakota School of Medicine & Health Sciences, Research Collaborator, Department of Neurology, Alzheimer’s disease Research Center, Mayo School of Graduate Education, College of Medicine, and first author of this study along with colleagues examined the cross-sectional association between COPD and MCI in individuals aged 70 to 89 years in the population-based Mayo Clinic Study of Aging.
The study included 1,927 individuals aged 70 to 89 years enrolled in the population-based Mayo Clinic Study of Aging. All study participants were evaluated by using a nurse assessment, neurological evaluation, and neuropsychological testing, and the diagnosis of MCI was made by a consensus panel according to the standardized criteria. Chronic obstructive pulmonary disease was identified by the review of medical records. The study was conducted from October 1, 2004, through July 31, 2007.
Among the participants 288 had COPD (men 18% women 12%). Participants with COPD had a 27% higher risk for MCI in comparison to patients without COPD (15% risk). The odds ratio for MCI was almost two times higher in patients with COPD than in those without. The effect was similar in men and women. The odds ratio for MCI increased from 1.60 in those with COPD duration of 5 years or less to 2.10i n patients with COPD duration of more than 5 years.
The researchers write in their conclusion “This study provides evidence that COPD is associated with increased odds of MCI and a-MCI. It also reports a dose-response relationship with the duration of COPD. Additional longitudinal studies in population-based cohorts are needed to determine whether COPD is indeed associated with the risk of incident MCI and dementia.”
The strengths of this study included; it is a population-based cross-sectional study, patients were randomly selected from a cohort of elderly individuals, the investigators making a diagnosis of COPD were blinded to the diagnosis of MCI, thus avoiding diagnostic suspicion bias and the diagnosis of the cognitive status of individuals was made by consensus among an examining physician/neurologist, a nurse, and a neuropsychologist.
But with every study comes limitations. The limitations for this study included; he study design was cross-sectional and precluded the researchers from concluding that there is a causal association between COPD and MCI and due to previous epidemiological studies has reported that COPD is underdiagnosed in the population the researchers note their estimates may be conservative.
This study is published in Mayo Clinic Proceedings.