In addition to the burden imposed by chronic obstructive pulmonary disease (COPD), patients often face co-occurring conditions such as diabetes, coronary artery disease, and osteoporosis.1 Emerging research also indicates that cognitive impairment is a common comorbidity in COPD, with studies showing prevalence as high as 52% in this patient population.2 “A number of suggestions have been made regarding the underlying pathophysiology, including cerebral hypoxia, loss of hippocampal volume and inflammatory mediator-related neuronal damage,” according to the results of a study published  in ERJ Open Research.2

As rates of cognitive impairment continue to increase due to the growing elderly population, it is especially important to elucidate the cognitive deficits associated with COPD and to differentiate these from the deficits observed in Alzheimer disease and other types of dementia. To that end, researchers conducted a narrative review and subsequent cross-sectional study to examine differences in the pattern of cognitive impairment in patients with COPD (n=44) compared with patients with Alzheimer-type dementia (n=17) and healthy controls (n=28). The Addenbrooke’s Cognitive Examination (ACE)-III was used to assess cognitive impairment and domain-specific deficits.2

According to the results, the prevalence of cognitive impairment was 50% (95% CI, 33.8%-66.2%) in patients with COPD vs 7% (95% CI, 9.0%-23.5%) in the control group. Significantly lower scores on the ACE-III were found in the COPD group vs controls (P <.001) and in the Alzheimer group compared with the COPD group (P =.019). In addition, the Alzheimer group demonstrated lower scores in the domains of attention (P =.004), memory (P =.004), and fluency (P =.001) compared with the COPD group.

In line with results from previous research,3,4 the current findings point to a higher prevalence of cognitive impairment in patients with COPD vs healthy controls and suggest that there are domain-specific differences in COPD-related cognitive impairment compared with Alzheimer dementia. “If confirmed, this would be clinically relevant for COPD management (eg, it might alter the ability to comply with particular treatment types or benefit from more complex therapies) and for care of their comorbid disease, as specific types of cognitive impairment may have different management strategies,” the investigators wrote.2

To learn more about the link between COPD and cognitive impairment, Pulmonology Advisor interviewed one of the study coauthors, Charlotte Morris, BSc, MBBCh, a researcher at University Hospitals Birmingham NHS Foundation Trust (UHB) in the United Kingdom; and Balwinder Singh, MD, MS, FAPA, assistant professor of psychiatry in the department of psychiatry and psychology, and director of the Mood Program at the Mayo Clinic in Rochester, Minnesota, who has also investigated the topic with his colleagues.3,4

Pulmonology Advisor: What is known thus far about cognitive impairment in COPD and what do your findings add to our understanding of this issue?

Dr Morris: There is increasing evidence in the published literature that patients with COPD are more likely to have cognitive impairment. What we do not know is whether people with COPD are more specifically affected in certain areas of cognition. Using a validated cognitive tool, we found that specific areas of cognition were affected differently in COPD compared with people with known Alzheimer-type dementia. We also found that when we compared the COPD group with the healthy control group, patients with COPD were significantly more likely to have cognitive impairment. 

Although these results are interesting and fit with results previously published in the literature, we must bear in mind that this was a small study and there could have been confounding effects.

Dr Singh: Patients with COPD have an increased risk for neuronal injury, either due to hypoxia or associated comorbidities, especially cardiovascular disease. Recent studies suggest that up to 77% of patients with both COPD and hypoxemia have some form of cognitive impairment.3 In a population-based, prospective cohort study of individuals aged 70 years and older (the Mayo Clinic Study of Aging), COPD was associated with a significant increase in the risk for incident mild cognitive impairment (MCI), specifically nonamnestic-MCI (na-MCI).3 The results remained significant after adjusting for several important covariates.

Further, there was a dose-response relationship: the risk for MCI increased with the duration of COPD. Thus, highlighting the importance of COPD as a risk factor for MCI may provide a substrate for early intervention to prevent the incidence or progression of MCI, particularly na-MCI.

Pulmonology Advisor: How should clinicians screen for and treat these issues in practice?

Dr Morris: My approach to this is to be more aware that people with COPD are at risk for cognitive impairment, and to consider testing for this if signs are shown by the patient and the patient agrees to be screened. Although there is no cure for cognitive impairment, early diagnosis and intervention could mean more appropriate support structures for individuals who are affected.  

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Dr Singh: There are several tools easily available for screening for cognitive impairment, such as the Short Test of Mental Status (STMS), the Montreal Cognitive Assessment (MoCA), and the Mini-Mental State Examination (MMSE). These cognitive screens usually take approximately 5 to 10 minutes. For patients who screen positive on these tests, a comprehensive neuropsychological evaluation could be considered. In the treatment of COPD, an evaluation by a pulmonologist can be considered.

Pulmonology Advisor: What are other relevant recommendations for clinicians?

Dr Morris: COPD is a multisystem disorder with far-reaching consequences way beyond the lungs. The majority of cases — but not all — are caused by tobacco smoking. One takeaway from this, and indeed any other study about COPD, is the urgent importance of helping our patients stop smoking to reduce their risk of developing COPD or COPD-related cognitive impairment in the future.

Based on this study and the other published literature, I think there is good evidence that people with COPD are more likely to have cognitive impairment, and awareness of this is important for our patients. 

Dr Singh: Patients with COPD are at high risk for cognitive impairment, and reducing the risk factors and treating COPD effectively may help reduce that risk. The presence of COPD may serve as a risk marker for MCI and may facilitate targeted preventive or therapeutic interventions. There is a need for further research in this field.

Pulmonology Advisor: What are the remaining needs in terms of research or education regarding this topic?

Dr Morris: In my view, further research is needed to establish whether there is COPD-associated cognitive impairment affecting different cognitive domains and caused by a different pathologic process than other dementias such as Alzheimer disease, or whether people with COPD are simply more likely to develop vascular dementia or Alzheimer than the general population. 

Dr Singh: For research, the increased risk for MCI associated with COPD can be explored further using biomarkers, neuroimaging, and genetic linkage analysis.

From the patient education perspective, I think it is important for patients to be aware of the risk for cognitive impairment with COPD. Smoking cessation reduces the risk for COPD, especially early in treatment, and thus may help reduce the risk for MCI. Identifying risk factors for MCI, the earliest symptomatic phase of Alzheimer disease, may help to identify ways to delay or prevent the onset of dementia, especially in the absence of a curative therapy for Alzheimer disease.

References

  1. Chatila WM, Thomashow BM, Minai OA, Criner GJ, Make BJ. Comorbidities in chronic obstructive pulmonary disease. Proc Am Thorac Soc. 2008;5(4):549-555.
  2. Morris C, Mitchell JW, Moorey H, Younan HC, Tadros G, Turner AM. Memory, attention and fluency deficits in COPD may be a specific form of cognitive impairment. ERJ Open Res. 2019;5(2):00229-2018.
  3. Singh B, Parsaik AK, Mielke MM, et al. Chronic obstructive pulmonary disease and association with mild cognitive impairment: the Mayo Clinic Study of Aging. Mayo Clin Proc. 2013;88(11):1222-1230.
  4. Singh B, Mielke MM, Parsaik AK, et al. A prospective study of chronic obstructive pulmonary disease and the risk for mild cognitive impairment. JAMA Neurol. 2014;71(5):581-588. 

This article originally appeared on Pulmonology Advisor