Table 1 -. Characteristics of the articles selected.
| Study | Design | Objective | Sample size and COPD severity | Characteristics of COPD participants | Intervention | Results/Conclusions |
|---|---|---|---|---|---|---|
| Dodd et al.(19) | Observational study | To assess neuropsychological performance in COPD patients hospitalized after an acute exacerbation and recovery, compared with patients with stable COPD and with healthy control subjects | 110 participants: | - | In patients hospitalized with an acute COPD exacerbation, impaired cognitive function is associated with worse health status and longer length of hospital stay. Cognitive function might not improve with recovery | |
| 30 COPD inpatients hospitalized following an exacerbation | Mean age, 70 ± 11 years; 15 (50%) were female | |||||
| 50 outpatients with stable COPD | Mean age, 69 ± 8 years; 28 (56%) were female | |||||
| 30 healthy control subjects | ||||||
| Chang et al.(20) | Cohort study | To determine the extent to which the co-occurrence of COPD and cognitive impairment leads to adverse health outcomes in older adults | 3,093 patients: | None | Patients with COPD and cognitive impairment had the highest rates of respiratory-related and all-cause hospitalizations and death | |
| 431 with COPD only | 188 (43.7%) were 65-70 years of age; 210 (48.7%) were female | |||||
| 29 with COPD and cognitive impairment | 6 (21.3%) were 65-70 years of age; 10 (34.5%) were female | |||||
| 114 with cognitive impairment only | ||||||
| 2,519 with neither COPD nor cognitive impairment | ||||||
| Dodd et al.(21) | Observational study | To evaluate whether there are significant differences between COPD patients and control subjects, in terms of white matter integrity and communication between gray matter resting-state networks, and to test the observed differences related to disease severity, comorbid cerebrovascular disease, and cognitive dysfunction | 25 non-hypoxemic COPD patients | Mean age, 67.8 ± 8.1 years; 11 (44%) were female | None | In stable, non-hypoxemic COPD, there is reduced white matter integrity throughout the brain and widespread disturbance in the functional activation of gray matter, which might contribute to cognitive dysfunction. White matter microstructural integrity is independent of smoking and comorbid cerebrovascular disease, but gray matter functional activation is not. The mechanisms remain unclear but could include cerebral small vessel disease caused by COPD |
| 25 control subjects | ||||||
| Villeneuve et al.(10) | Observational study | To determine the frequency and subtypes of MCI in COPD patients and to assess the validity of two cognitive screening tests (the MMSE and MoCA) in detecting MCI in COPD patients | 45 patients with moderate-to-severe COPD | Mean age, 68.84 ± 8.43 years; 29 (64%) were female | None | In this preliminary study, a substantial proportion of COPD patients were found to have MCI. The MoCA was better than was the MMSE at detecting MCI in COPD patients. |
| 50 healthy control subjects | ||||||
| Martin et al.(22) | Clinical trial | To determine the effect of hypoxia on cognitive performance in COPD patients with PaO2 <6.6 kPa | 10 patients with moderate-to-severe COPD | Mean age, 64 years; 3 (30%) were female | For a short period of time, patients breathed 21% O2 when PaO2 was < 6.6 kPa | Short-term exposure to hypoxia had no adverse effect on cognitive function |
| Pereira et al.(23) | Clinical trial | To evaluate the effect of a multidisciplinary pulmonary rehabilitation program on cognitive function in COPD patients, adjusting for potential confounders | 34 patients with moderate-to-severe COPD | Mean age, 65.2 ± 7 years; 17 (50%) were female | 3-month program of pulmonary rehabilitation | Even after adjusting for the sociodemographic factors that might affect cognitive function, the authors found that pulmonary rehabilitation improved cognitive performance in COPD patients. There were gender- and age-related differences in cognitive scores that persisted after rehabilitation |
| 18 healthy control subjects | ||||||
| Klein et al.(24) | Cohort study | To explore the influence of COPD on attentional functions, learning, and logical thinking | 60 COPD patients | Mean age, 63.2 ± 9.8 years; 24 (40%) were female | None | In COPD patients, there was global impairment in cognitive functions that was negatively influenced by advancing age and increased in proportion to the degree of disease severity |
| 60 control subjects | ||||||
| Thakur et al.(25) | Cohort study | To elucidate the association between COPD and the risk of cognitive impairment, in comparison with control subjects without COPD | 1,202 COPD patients | Mean age, 58.2 ± 6.2 years; 691 (57.4%) were female | None | COPD is a major risk factor for cognitive impairment. In COPD patients, hypoxemia is a major contributor to cognitive impairment and regular use of home oxygen is a protective factor. Health care providers should consider screening COPD patients for cognitive impairment |
| 302 control subjects | ||||||
| Antonelli-Incalzi et al.(14) | Observational study | To assess whether certain neuropsychological patterns are associated with various limitations to physical independence in COPD patients | 149 COPD patients | 112 (75.2%) were over 65 years of age; 14 (9.4%) were female | None | Classic indicators of the severity of COPD showed no correlation with personal autonomy |
| Borson et al.(26) | Observational study | To model the relationship between respiratory failure and domains related to brain function, including low mood, subtly impaired cognition, systemic inflammation, and structural/neurochemical brain abnormalities | 9 healthy control subjects | None | COPD is associated with slight decreases in mood and cognition. Severe COPD is associated with chronic systemic inflammation and subtle cognitive deficits (on digit symbol coding tasks). Levels of oxygen desaturation appear to mediate specific changes in brain neurochemistry and structure that suggest sustained brain damage | |
| 18 COPD patients, half of whom were oxygen-dependent | Mean age, 68.5 ± 8.0 years; 11 (64%) were female | |||||
| Orth et al.(27) | Observational study | To analyze driving performance in COPD patients and healthy control subjects | 17 COPD patients | Mean age, 55.2 ± 9.3 years | None | Compared with healthy control subjects, COPD patients are more likely to cause a traffic accident. Impaired driving performance in COPD patients cannot be predicted on the basis of the severity of the disease |
| 10 healthy control subjects | ||||||
| Pinto de Lima et al.(28) | Observational study | To test the hypothesis that clinically stable COPD patients without overt cognitive symptoms can nonetheless have subtle cognitive impairment | 30 COPD patients | Mean age, 65 ± 8 years; 10 (33%) were female | None | There might be subclinical encephalopathy in COPD, characterized by subtle impairment of global cognitive ability |
| 34 control subjects | 24 (71%) were female | |||||
| Salik et al.(29) | Observational study | To determine the relationship between cognitive function and quality of life in COPD patients with mild hypoxemia and moderate airway obstruction | 32 patients with moderate stable COPD | Mean age, 66.7 ± 2.5 years; 14 (44%) were female | None | Cognitive function in COPD patients with hypoxemia might not be impaired despite their poor quality of life status |
| 26 healthy subjects | ||||||
| Antonelli-Incalzi et al.(30) | Observational study | To evaluate the prognostic role of cognitive impairment in patients with severe COPD | 149 COPD patients who had undergone a period of in-hospital rehabilitation following an acute exacerbation | Mean age, 68.7 ± 8.5 years; 22 (16.4%) were female | None | Impaired drawing ability is a risk factor for mortality and its testing might improve the assessment of hypoxemic COPD patients |
| Corsonello et al.(31) | Observational study | To determine whether cancer is more disabling than are other chronic diseases that are highly prevalent in the elderly | 6 groups of patients: | None | Cognitive impairment was more prevalent in patients with congestive heart failure or COPD than in those with cancer | |
| Congestive heart failure (n = 832) | ||||||
| Diabetes mellitus (n = 939) | ||||||
| COPD (n = 399) | 178 (44.6%) were 65-79 years of age; 147 (36.8%) were female | |||||
| Non-metastatic solid tumors (n = 813) | ||||||
| Metastatic solid tumors (n = 259) | ||||||
| Leukemia/lymphoma (n = 326) | ||||||
| Antonelli-Incalzi et al.(32) | Observational study | To determine whether the neuropsychological performance of untreated patients with OSA conforms to a distinctive pattern | 49 newly diagnosed, untreated OSA patients | None | A minority of newly diagnosed OSA patients had distinct neuropsychological impairment. The greater body mass index of cognitively impaired OSA patients indicates that the metabolic syndrome might also be causally related to the cognitive dysfunction | |
| 27 patients with multi-infarct dementia | ||||||
| 31 patients with mild-to-moderate dementia of the Alzheimer type | ||||||
| 63 patients with severe COPD |
MMSE: Mini-Mental State Examination; MoCA: Montreal Cognitive Assessment; MCI: mild cognitive impairment; kPa: kilopascal; CHF: congestive heart failure; and OSA: obstructive sleep apnea.