COPD Linked to Increased Risk of Cognitive Impairment

Patients with chronic obstructive pulmonary disease (COPD) are at a higher risk of developing cognitive impairment or dementia, according to a study published in BMJ Open Respiratory Research.¹

Cognitive impairment affects various mental functions, impacting patients’ quality of life and social interaction capabilities to varying degrees.² Past studies found that between 16% and 57% of individuals with COPD experience cognitive impairment.¹ The researchers attributed the wide discrepancies in prevalence rates to the diversity in study designs, inclusion criteria, participant age ranges, and the methodologies and tools used for assessment.

Cognitive deficits impair several cognitive domains in patients with COPD, such as processing speed and executive function. This further deteriorates their self-management skills, personal independence, and medication adherence, resulting in a diminished quality of life. Based on disease severity, cognitive impairment in those with COPD is classified into mild cognitive impairment (MCI) and dementia. MCI is further subdivided into amnestic MCI (A-MCI) and non-amnestic MCI (na-MCI) depending on the presence of memory loss.

Past studies identified shared risk factors for both COPD and cognitive impairment, including aging, sleep disorders, and comorbidities. Despite this, the relationship between COPD and cognitive impairment has not yet been well described. Therefore, the researchers conducted a systematic review to investigate whether COPD is an independent risk factor for cognitive impairment.

Patients with chronic obstructive pulmonary disease (COPD) are at an increased risk of cognitive impairment, with a higher likelihood of developing non-amnestic mild cognitive impairment (na-MCI). | Image Credit: Atlas - stock.adobe.com

They searched for studies in databases like PubMed, Cochrane Library, and MEDLINE from inception to December 1, 2022, to identify relevant articles published in English or Chinese. The researchers manually screened the included studies to ensure they captured all eligible studies. More specifically, 2 investigators independently extracted data from selected studies and assessed their eligibility.

Additionally, the 2 investigators assessed the quality of cohort studies using the Newcastle-Ottawa Quality Assessment Scale for Cohort Studies (NOS). It evaluates studies across 3 critical dimensions: the selection of the study population, the comparability of those being studied, and the accuracy of the outcome assessment.

The NOS uses a star system, where the highest quality studies can earn up to 1 star for each criterion within the selection and outcome categories; the comparability category is an exception as studies can be awarded up to 2 stars. Therefore, a study’s NOS score can range from zero to 9 stars. Lastly, the 2 researchers extracted various data, including the year of publication, the sample size, and outcomes.

The initial search retrieved 2438 studies, but the researchers ultimately analyzed 10, encompassing 625,644 participants. Geographically, 7 studies were conducted in China, while the US, Finland, and the United Kingdom (UK) each contributed 1 study.

Each study included exposure and control groups and was published between 2012 and 2020. The topics investigated across studies included dementia, bipolar disorder, MCI, and other mental dysfunctions like cognitive impairment, Parkinson disease, and vascular dementia. Based on the NOS, all studies were high quality, with scores ranging from 7 to 9 stars.

The researchers found that the HR comparing cognitive impairment in patients with COPD to those without COPD ranged from 0.91 to 2.23, indicating variability in the risk assessment across studies; the duration and follow-up timelines also varied across studies, adding to the data’s heterogeneity. Using a random-effects model, they determined the aggregated HR for cognitive impairment in patients with COPD to be 1.39 (95% CI, 1.25-1.54; I2 = 89%; P < .01), highlighting a significant association between them.

Additionally, the subgroup analyses explored the impact of COPD on cognitive impairment across different demographics, like age, sex, and disease classifications. Although they adjusted for confounding factors, the researchers found no statistically significant differences in cognitive impairment risk among patients with COPD when analyzed by sex or age categories. However, they observed a significant distinction between the risks for a-MCI (HR, 0.63-1.52; P = .002) and na-MCI (HR, 2.36; 95% CI, 1.68-3.31; P = .002), suggesting a higher likelihood for patients with COPD to develop na-MCI.

The researchers acknowledged their limitations, one being that they could not perform a subgroup analysis considering COPD severity, comorbidities, or acute exacerbation instances due to a lack of detailed data across studies. This narrows the scope of their findings and weakens the evidence of a direct link between cognitive impairment and COPD. Despite their limitations, the researchers expressed confidence in their findings and used them to emphasize the importance of early identification of cognitive impairment.

“Regular monitoring for cognitive impairment is imperative to ensure timely identification and management of cognitive decline for patients with COPD,” the authors concluded. “Such proactive approaches can substantially aid in optimizing the prognosis and enhancing the quality of life for patients with COPD, making cognitive assessment an essential component of comprehensive care for these individuals.”

References

1. Chen X, Yu Z, Liu Y, Zhao Y, Li S, Wang L. Chronic obstructive pulmonary disease as a risk factor for cognitive impairment: a systematic review and meta-analysis. BMJ Open Respir Res. 2024;11(1):e001709. doi:10.1136/bmjresp-2023-001709
2. Academy of Cognitive Disorders of China (ACDC), Han Y, Jia J, et al. Expert consensus on the care and management of patients with cognitive impairment in China. Neurosci Bull. 2020;36(3):307-320. doi:10.1007/s12264-019-00444-y