Longitudinal and genetic effects in the relationship between pulmonary function and cognitive performance.

Previous studies have found cognitive deficits in patients with impaired pulmonary function, and recent data from healthy older adults suggest an association of pulmonary function with cognitive function. This 6-year longitudinal study evaluated genetic and environmental sources of covariation in the association of pulmonary function and cognitive performance. The sample included 222 Swedish twin pairs (60% women) with a mean age of 62.3 (+/- 7.7) years (age range: 40-84). Hierarchical multiple regression analyses, controlling for the effects of age, gender, and height, were employed to predict performance on cognitive tests of fluid intelligence (Digit Symbol, Block Design, Digit Span-Backward) and crystallized intelligence (Information) from forced expiratory volume in one second (FEV1). Bivariate cross-twin correlations were used to evaluate the contribution of genetic and environmental factors in the association of pulmonary function and cognitive performance. Results indicated that FEV1 predicted performance on tests of fluid intelligence but not crystallized intelligence at the initial assessment and at the 6-year follow-up. Cross-twin correlational analyses indicated that genetic effects accounted for a greater share of the association of pulmonary function and cognitive performance than environmental effects, but environment also accounted for a substantial share of the covariance.