An association has been shown between reduced lung function and impaired cognition in numerous observational studies. Important health outcomes are widely affected by cognitive dysfunction and it is also a precursor to dementia, but the treatment options to address this concern are currently very limited. It is, therefore, of prime importance to identify the modifiable risk factors to prevent cognitive decline and preserve cognition. A study determined if lung function or risk of COPD causes reduced cognitive function using Mendelian randomization (MR).

Single nucleotide polymorphisms from genome wide association studies of lung function and COPD were utilized for the study as exposures. The researchers examined their effect on general cognitive function deploying a sample of 132,452 individuals. It was then subjected to multivariable MR (MVMR), to examine the effect of lung function before and after conditioning for covariates.

The results of the study were as follows-

• Weak evidence was found regarding reduced lung function or increased liability to COPD causing lower cognitive function.
• MVMR demonstrated reduced FEV1 and reduced FVC to cause lower cognitive function, but conditioning for height (− 0.03 and − 0.01 for FEV1 and FVC respectively) and educational attainment (− 0.03 and − 0.01) weakened the evidence.

Thus, the researchers could not find any evidence associating reduced lung function or COPD to reduced cognitive function. They rendered previous observational studies to be probably affected by residual confounding and urged researchers to focus on shared risk factors for reduced lung function and cognition, rather than lung function alone as a modifiable risk factor.

Higbee, D.H., Granell, R., Hemani, G. et al. Lung function, COPD and cognitive function: a multivariable and two sample Mendelian randomization study. BMC Pulm Med 21, 246 (2021). https://doi.org/10.1186/s12890-021-01611-6