Background Cognitive impairment has been demonstrated in up to 77% of patients with COPD and hypoxaemia,1 however it is unclear if this impairment is due to cognitive loss or was present before disease onset. In addition the evidence for impairment is less clear in patients with mild disease without hypoxaemia.
Methods Detailed neuropsychological testing of 44 non-exacerbating, non-hypoxaemic patients with COPD. Other physiological, and health status data were collected. Standardised neuropsychological scores were generated from age, gender and education related normative population samples. Cognition is considered moderately or severely impaired if a standardised score lie ≥1 or 2 standard deviations (SD) respectively from the normative population mean. The use of population normal range is valid given that the group have a normal estimated Full Scale IQ. Estimates of an individuals predicted cognitive performance in attention and processing speed are derived from their adult reading ability, which is stable over time and largely resistant to cognitive decline. Individuals performing below their predicted performance are judged to have suffered cognitive loss. This methodology has advantages over control group comparisons since the individual acts their own control allowing for calculations of what is ‘normal’ for that individual.
Results 44 patients, 52% Females, Mean Age 68±8 years, FEV1pp 49±20%, PaO2 10±2 kPa, Pack Years. smoking 57 (41–69), 6MWD 387m (359–458), BMI 26 (23–29), SGRQ 52±19, Hospital Anxiety and Depression Scale 12 (6–19), Fatigue (FACIT-F) 18 (9–25), Estimated Full Scale IQ 96. In terms of cognitive loss, 25% had significant loss in processing speed and 30% in working memory. The proportion of patients whose cognitive scores were 1 and 2 SD's below predicted are tabulated.
Conclusion Up to one third of stable non-hypoxaemic patients with COPD demonstrate significant cognitive loss. A significant proportion have severe impairment of memory and executive function. The cause and implications of this cognitive loss should be the focus of future research.