Chronic obstructive pulmonary disease (COPD) and dementia are both extremely widespread chronic diseases with a significant impact on world health. The most common comorbidity of COPD is dementia, leading to an increased need for hospitalisation, difficulties with daily functioning, an increased need for care services, and rate of mortality. 4% and 61% of patients with COPD reported developing cognitive impairment. Alteration in cerebral perfusion in patients with COPD results from hypoxemia, which is an abnormal decrease in oxygen in the blood, and these changes contribute to the development of cognitive decline. Long-term hypoxia, hypercapnia, and increased inflammatory cytokines in COPD patients contribute to the development of degenerative brain diseases (including structural changes in the brain and reduced white matter integrity). Psychomotor speed, executive function ,planning, verbal memory, and cognitive flexibility are cognitive domains affected in patients with COPD. The risk of dementia increases with age but is unaffected by gender.