Cognitive dysfunction in severe chronic obstructive pulmonary disease (COPD) with or without Long-Term Oxygen Therapy (LTOT)

BACKGROUND: Chronic Obstructive Pulmonary Disease (COPD) is a progressive respiratory condition which can lead to comorbidities of variable severity, cognitive dysfunction included. The role of supplemental oxygen in preventing COPD-induced cognitive deterioration is still debated, but only episodically investigated. The aim of this study was to compare the cognitive pattern of hypoxemic COPD subjects treated with long-term oxygen (LTOT) to that of patients of comparable severity assuming oxygen on irregular basis, and to normal reference values. METHODS: Lung function, arterial blood gases, health status, and cognitive function measured by means of four psychometric tests focusing different domains of cognition (such as: MMSE, Clock test; TMT-A; TMT-B) were assessed in 146 well matched hypoxemic COPD patients (males n = 96, 66%; mean age = 70.5 ± 12.9). Seventy-three patients were assuming long-term oxygen (LTOT), while the remaining seventy-three were only using oxygen as needed (AN). Regarding statistics, t test and ANOVA (Duncan test) were used to analyze data, assuming a p < 0.05 as the lowest limit of significance. RESULTS: Even though all COPD patients showed a poorer psychometric profile vs corresponding normal reference values, LTOT patients showed a lower prevalence of severe deterioration in cognition. Also the extent of impairment was significantly lower in these patients when assessed by TMT-A and TMT-B (p < 0.012 and 0.001, respectively), but not when measured by MMSE and Clock test (both p = ns). Several domains of cognition are variably affected by persistent hypoxemia in COPD patients. A panel of psychometric tools is needed for identifying the pattern of cognitive dysfunctions in these patients. Memory and attention (functions assessed by MMSE and Clock test) are only mildly-moderately affected, while visual processing, reproduction of numeric sequences, cognition flexibility, and shifting capacity (functions assessed by TMT-A and TMT-B) are much more deteriorated (p < 0.012 and p < 0.001, respectively). CONCLUSIONS: Only LTOT allows to preserve significantly (p < 0.022) cognitive functions from the COPD-induced deterioration. This assumption is of strategic value for COPD patients who are prescribed long-term oxygen because they frequently are not aware of the cognitive risks related to their condition.