COPD, Dementia, and Smoking

Editorial

Austin J Pulm Respir Med 2014;1(2): 1008.

COPD, Dementia, and Smoking

Takeharu Koga*

Department of Respiratory Medicine, Asakura Medical Association Hospital, Raiharu 422-1, Asakura 838-0069, Japan

*Corresponding author: Takeharu Koga, Department of Respiratory Medicine, Asakura Medical Association Hospital, Raiharu 422-1, Asakura 838- 0069, Japan

Received: February 10, 2014; Accepted: February 19, 2014; Published: February 22, 2014

Editorial

COPD is projected to cause more than 6 million deaths annually, ranking as the third most common cause of death in the world [1]. On the other hand, cognitive dysfunction is gaining attention as a surging health problem worldwide, for instance, dementia is forecasted to affect 36 million people with annual cost of $600 billion [2]. Are there any relationships between these two expanding heath dooms of the world?

First of all, although the relationships remain to be established [3], several studies have indicated that COPD is associated with cognitive dysfunction [4,5]. Not only patients with severe COPD [6], or those lowered oxygen saturation [7] have impaired cognitive function, but also duration of COPD [8] or reduced expiratory pulmonary function [9] can be associated with exaggerated cognitive decline. In concert with these observations, brain imaging has documented that patients with COPD have hippocampal atrophy, suggesting a pathological basis of the cognitive dysfunction [10].

Second, these two disorders can affect each other, resulting in a lowered quality of life of affected individuals. For instance, a recent study showed that impaired cognitive function is associated with worse health status and longer hospital length of stay in patients hospitalized with an acute COPD exacerbation, and a significant proportion of patients are discharged home with unrecognized mild to severe cognitive impairment, which may not improve with recovery [11].

Third, COPD and dementia may share common pathogenesis. Epidemiological studies have noted that the prevalence of COPD [12] and dementia [13] is higher among people with lower socioeconimic class. Air pollution, an important culprit for the development of COPD, can be associated with cognitive decline [14]. In addition to these, smoking should be nominated as another common risk factor. Smoking is the established most important risk factor for COPD, and can also be for dementia.

Earlier case–control studies have indicated that smoking is not associated with AD [15], or even associated with a reduced risk of AD [16]. However, more recent longitudinal studies, but not all [17], have documented that current smoking is associated with dementia [18] and cognitive dysfunction [19,20]. Not only active smoking, but also passive smoking may contribute to cognitive decline in never and former smokers [21]. Furthermore, in concert with the deleterious effects of environmental tobacco smoke, investigations with animal models have documented that an exposure to cigarette smoke [22] or nicotine [23] results in neuropathological alterations identical to those in AD.

Above mentioned notions stress an important link between the two dooming chronic health conditions, and imply “synergistic” negative impact on quality of life. Since COPD and dementia are both progressive and currently lack effective treatment, preventions and interventions at an early stage to minimize the functional decline are necessary. Therefore, better strategies are needed to evaluate and manage COPD and cognitive impairment concurrently in order to optimize health outcomes, along with better understanding of underlying mechanisms and treatment of cognitive dysfunction in COPD. For now, smoking cessation appears to be most promising. Smoking cessation has been positioned as essential for patients with COPD: it may prevent or slower the progression of the disease, depending on the status of the disease and more complex factors such as genetic and environmental interactions. Is smoking cessation also beneficial for dementia? Notably, it has been suggested that sustained smoking cessation for a prolonged period relieves the risk of dementia [24], and alleviates the decline in cognitive function in the elderly [20]. Thus, smoking cessation should also be a part of the management of patients with COPD complicated by cognitive dysfunction.

It is becoming clear that COPD should be noted not only as a health threat by itself but also as having propensity to accompany various other common diseases such as cardiovascular diseases and malignancies [25]. Cognitive dysfunction should be noted as another co-morbidity of COPD, and nominated as diseases which can be prevented by smoking cessation.

References

  1. Lozano R, Naghavi M, Foreman K, Lim S, Shibuya K, Aboyans V, et al. Global and regional mortality from 235 causes of death for 20 age groups in 1990 and 2010: a systematic analysis for the Global Burden of Disease Study 2010. Lancet. 2012; 380: 2095-2128.
  2. Wimo A. World Alzheimer Report 2010: The Global Econoic Impact of Dementia. Alzheimer’s Desease International: London, UK, 2010.
  3. Schou L, Ostergaard B, Rasmussen LS, Rydahl-Hansen S, Phanareth K. Cognitive dysfunction in patients with chronic obstructive pulmonary disease--a systematic review. Respiratory medicine. 2012; 106: 1071-1081.
  4. Li J, Huang Y, Fei GH. The evaluation of cognitive impairment and relevant factors in patients with chronic obstructive pulmonary disease. Respiration. 2013; 85: 98-105.
  5. Liesker JJ, Postma DS, Beukema RJ, ten Hacken NH, van der Molen T, Riemersma RA, et al. Cognitive performance in patients with COPD. Respir Med. 2004; 98: 351-356.
  6. Hung WW, Wisnivesky JP, Siu AL, Ross JS. Cognitive decline among patients with chronic obstructive pulmonary disease. Am J Respir Crit Care Med. 2009; 180: 134-137.
  7. Thakur N, Blanc PD, Julian LJ, Yelin EH, Katz PP, Sidney S, et al. COPD and cognitive impairment: the role of hypoxemia and oxygen therapy. Int J Chron Obstruct Pulmon Dis. 2010; 5: 263-269.
  8. Singh B, Parsaik AK, Mielke MM, Roberts RO, Scanlon PD, Geda YE, et al. Chronic obstructive pulmonary disease and association with mild cognitive impairment: the Mayo Clinic Study of Aging. Mayo Clin Proc. 2013; 88: 1222- 1230.
  9. Vidal JS, Aspelund T, Jonsdottir MK, Jonsson PV, Harris TB, Lopez OL, et al. Pulmonary function impairment may be an early risk factor for late-life cognitive impairment. J Am Geriatr Soc. 2013; 61: 79-83.
  10. Li J, Fei GH. The unique alterations of hippocampus and cognitive impairment in chronic obstructive pulmonary disease. Respir Res. 2013; 14: 140.
  11. Dodd JW, Charlton RA, van den Broek MD, Jones PW. Cognitive dysfunction in patients hospitalized with acute exacerbation of COPD. Chest. 2013; 144: 119-127.
  12. Kainu A, Rouhos A, Sovijarvi A, Lindqvist A, Sarna S, Lundback B. COPD in Helsinki, Finland: socioeconomic status based on occupation has an important impact on prevalence. Scand J Public Health. 2013; 41: 570-578.
  13. Yaffe K, Falvey C, Harris TB, Newman A, Satterield S, Koster A, et al. Effect of socioeconomic disparities on incidence of dementia among biracial older adults: prospective study. 2013; 347: f7051.
  14. Gatto NM, Henderson VW2, Hodis HN3, St John JA3, Lurmann F4, Chen JC5, et al. Components of air pollution and cognitive function in middle-aged and older adults in Los Angeles. Neurotoxicology. 2014; 40: 1-7.
  15. Cooper JK, Mungas D. Risk factor and behavioral differences between vascular and Alzheimer’s dementias: the pathway to end-stage disease. J Geriatr Psychiatry Neurol. 1993; 6: 29-33.
  16. Lee PN. Smoking and Alzheimer’s disease: a review of the epidemiological evidence. Neuroepidemiology. 1994; 13: 131-144.
  17. Wang CC, Lu TH, Liao WC, Yuan SC, Kuo PC, Chuang HL, et al. Cigarette smoking and cognitive impairment: a 10-year cohort study in Taiwan. Arch Gerontol Geriatr. 2010; 51: 143-148.
  18. Anstey KJ, von Sanden C, Salim A, O’Kearney R. Smoking as a risk factor for dementia and cognitive decline: a meta-analysis of prospective studies. Am J Epidemiol. 2007; 166: 367-378.
  19. Nooyens AC, van Gelder BM, Verschuren WM. Smoking and cognitive decline among middle-aged men and women: the Doetinchem Cohort Study. Am J Public Health. 2008; 98: 2244-2250.
  20. Sabia S, Elbaz A, Dugravot A, Head J, Shipley M, Hagger-Johnson G, et al. Impact of smoking on cognitive decline in early old age: the Whitehall II cohort study. Archives of general psychiatry. 2012; 69: 627-635.
  21. Akhtar WZ, Andresen EM, Cannell MB, Xu X. Association of blood cotinine level with cognitive and physical performance in non-smoking older adults. Environ Res. 2013; 121: 64-70.
  22. Moreno-Gonzalez I, Estrada LD, Sanchez-Mejias E, Soto C. Smoking exacerbates amyloid pathology in a mouse model of Alzheimer’s disease. Nat Commun. 2013; 4: 1495.
  23. Oddo S, Caccamo A, Green KN, Liang K, Tran L, Chen Y, et al. Chronic nicotine administration exacerbates tau pathology in a transgenic model of Alzheimer’s disease. Proc Natl Acad Sci U S A. 2005; 102: 3046-30451.
  24. Mons U, Schöttker B, Müller H, Kliegel M, Brenner H. History of lifetime smoking, smoking cessation and cognitive function in the elderly population. Eur J Epidemiol. 2013; 28: 823-831.
  25. Konstantakaki M, Tzartos SJ, Poulas K, Eliopoulos E. Model of the extracellular domain of the human alpha7 nAChR based on the crystal structure of the mouse alpha1 nAChR extracellular domain. J Mol Graph Model. 2008; 26: 1333-1337.

Download PDF

Citation: Koga T. COPD, Dementia, and Smoking. Austin J Pulm Respir Med 2014;1(2): 1008. ISSN:2381-9022

Home
Journal Scope
Online First
Current Issue
Editorial Board
Instruction for Authors
Submit Your Article
Contact Us