The Relationships Among Pulmonary Function, Aerobic Fitness, and Cognitive Functioning in Older COPD Patients: SpeedSpeed
Results of the regression analysis indicated that education and CESD did not predict a significant portion of the variance in speed of processing (F2,31 = 1. 24; p > 0.05). Distance on the 6-min walk test was stepped into the equation as a significant predictor of speed of processing (Fchange130 = 8.17; p < 0.01; r2change = 0.20, (3 = —1.18). Then, MVV was stepped into the equation and further contributed to the explanation of the variance (Fchange129 = 5.81; p < 0.03; r2change = 0.16; 3 = 9.17). Finally, age added further to the prediction of the variance (Fchange128 = 5.26; p < 0.03; r2change = 0.10; 3 = 25.43). Thus, 6-min walk distance, age, and MVV predicted 46% of the variance in speed of processing (F5,25 = 5. 45; p < 0.01). None of the other predictors reached the criterion required for entrance into the equation.
Span
Education and CESD did not predict a significant portion of the variance in performance (F2 26 = 1.44; p > 0.05). However, the addition of FVC did allow for the prediction of a significant proportion of the variance in performance (Fchange125 = 6.37; p < 0.02; r2change = 0.18; 3 = 0.59).

Stopping
The temporal location of the stopping signal relative to the stimulus had the predicted impact on the subjects’ ability to inhibit their response. The mean accuracy was as follows: at 75 ms, 0.69; 150 ms, 0.65; 225 ms, 0.62; and 300 ms, 0.55.
The ability to inhibit a response was not significantly predicted by education or depression (F2,89 = 24; p > 0.05). None of the other variables was a significant predictor of the variance in accuracy.
Discussion
It has been proposed that the mechanism underlying the negative relationship between age and cognitive functioning is cerebral oxygenation. Further, it has been proposed that an explanation for individual differences in cognitive functioning among older adults may be aerobic fitness level because of its impact on cerebral oxygenation. Patients with COPD may have a reduced Vo2peak for several reasons. These patients may be limited by their cardiovascular system, similar to normal healthy individuals and cardiac patients, or they may have pulmonary abnormalities that impose limitations in oxygen transport. Therefore, examination of these patients may provide clues as to the relationship between aerobic fitness, age, and cognitive functioning. To examine these relationships, cognitive performance on a variety of tasks was assessed in a sample of older adults with COPD, and prediction equations were generated using age, measures of pulmonary function, measures of oxygen saturation, and measures of aerobic fitness.