Better lung function may protect against coronary artery disease, stroke and type 2 diabetes

A study by the University of Hong Kong (HKU) has revealed a causal link between better lung function and reduced risk of coronary artery disease (CAD), stroke and type 2 diabetes mellitus (T2DM).

As one of the first and largest studies assessing the causal relationship between lung function and cardiovascular diseases (CVD) and T2DM using Mendelian randomization, this study showed that each standard deviation (SD) increase in forced expiratory volume in 1 second (FEV₁) and forced vital capacity (FVC) was associated with a CAD risk reduction of 28 percent (odds ratio [OR], 0.72; 95 percent confidence interval [CI], 0.63 to 0.82) and 30 percent (OR, 0.70; 95 percent CI, 0.62 to 0.78), respectively. [Thorax 2021;doi:10.1136/thoraxjnl-2020-215600]

The risk of overall stroke was also reduced, by 13 percent (OR, 0.87; 95 percent CI, 0.77 to 0.97) for each SD increase in FEV₁ and by 10 percent (OR, 0.90; 95 percent CI, 0.82 to 1.00) for each SD increase in FVC, with similar risk reductions observed with some stroke subtypes.

Higher FEV₁ was associated with lower risk of ischaemic stroke (OR per SD increase, 0.87; 95 percent CI, 0.77 to 0.99), small vessel stroke (OR per SD increase, 0.78; 95 percent CI, 0.61 to 1.00), and large artery stroke (OR per SD increase, 0.69; 95 percent CI, 0.54 to 0.89). Similar associations were seen between FVC and these stroke subtypes.

FEV₁ and FVC were also inversely associated with T2DM (OR per SD increase in FEV₁, 0.75; 95 percent CI, 0.62 to 0.90) (OR per SD increase in FVC, 0.67; 95 percent CI, 0.58 to 0.79).

“In previous observational studies, lung function was found to be inversely associated with CVD. However, these associations could be confounded by factors such as smoking, physical activity and height,” the researchers noted.

Using Mendelian randomization, the researchers extracted genetic variants related to the lung function parameters of FEV₁ and FVC from UK Biobank (n=421,986) and applied them to large genome-wide association studies (n≤1,030,836) to assess their relationship with CVD and T2DM.

Mendelian randomization is less likely to be affected by confounding factors than observational studies because it uses genetic variants related to exposures that are randomly allocated during conception.

“Our study highlights the role of lung function in maintaining good cardiovascular health, using a less biased design,” said first author, Dr Ryan Shiu-Lun Au Yeung of the School of Public Health, HKU.

From a clinical perspective, results of the study support interventions that improve lung function, such as smoking cessation and increased physical activities, to prevent CAD, stroke and T2DM. It also demonstrates the importance of big data in helping researchers understand the causes of diseases.

However, this study used databases that were predominantly derived from European population. According to the researchers, a biobank specific for Asians is crucial to provide evidence for Asian populations.

“This is particularly important because some diseases, such as haemorrhagic stroke and nasopharyngeal cancer, are more common in Asian populations. As such, it would be better to study the causes of these diseases using Asian databases,” Au Yeung added.