Genome-wide association study of preserved ratio impaired spirometry (PRISm).

BACKGROUND: Preserved ratio impaired spirometry (PRISm) is defined as a forced expiratory volume in 1 s (FEV1) <80% predicted and FEV1/forced vital capacity ≥0.70. PRISm is associated with respiratory symptoms and comorbidities. Our objective was to discover novel genetic signals for PRISm and see if they provide insight into the pathogenesis of PRISm and associated comorbidities. METHODS: We undertook a genome-wide association study (GWAS) of PRISm in UK Biobank participants (Stage 1), and selected single nucleotide polymorphisms (SNPs) reaching genome-wide significance for replication in 13 cohorts (Stage 2). A combined meta-analysis of Stage 1 and Stage 2 was done to determine top SNPs. We used cross-trait linkage disequilibrium score regression to estimate genome-wide genetic correlation between PRISm and pulmonary and extrapulmonary traits. Phenome-wide association studies of top SNPs were performed. RESULTS: 22 signals reached significance in the joint meta-analysis, including four signals novel for lung function. A strong genome-wide genetic correlation (rg) between PRISm and spirometric COPD (rg=0.62, p<0.001) was observed, and genetic correlation with type 2 diabetes (rg=0.12, p=0.007). Phenome-wide association studies showed that 18 of 22 signals were associated with diabetic traits and seven with blood pressure traits. CONCLUSION: This is the first GWAS to successfully identify SNPs associated with PRISm. Four of the signals, rs7652391 (nearest gene MECOM), rs9431040 (HLX), rs62018863 (TMEM114) and rs185937162 (HLA-B), have not been described in association with lung function before, demonstrating the utility of using different lung function phenotypes in GWAS. Genetic factors associated with PRISm are strongly correlated with risk of both other lung diseases and extrapulmonary comorbidity.

Lung function and cardiovascular disease: a two-sample Mendelian randomisation study.

BACKGROUND: Observational studies suggest an association between reduced lung function and risk of coronary artery disease and ischaemic stroke, independent of shared cardiovascular risk factors such as cigarette smoking. We use the latest genetic epidemiological methods to determine whether impaired lung function is causally associated with an increased risk of cardiovascular disease. METHODS AND FINDINGS: Mendelian randomisation uses genetic variants as instrumental variables to investigate causation. Preliminary analysis used two-sample Mendelian randomisation with lung function single nucleotide polymorphisms. To avoid collider bias, the main analysis used single nucleotide polymorphisms for lung function identified from UKBiobank in a multivariable Mendelian randomisation model conditioning for height, body mass index and smoking.Multivariable Mendelian randomisation shows strong evidence that reduced forced vital capacity (FVC) causes increased risk of coronary artery disease (OR 1.32, 95% CI 1.19-1.46 per standard deviation). Reduced forced expiratory volume in 1 s (FEV1) is unlikely to cause increased risk of coronary artery disease, as evidence of its effect becomes weak after conditioning for height (OR 1.08, 95% CI 0.89-1.30). There is weak evidence that reduced lung function increases risk of ischaemic stroke. CONCLUSION: There is strong evidence that reduced FVC is independently and causally associated with coronary artery disease. Although the mechanism remains unclear, FVC could be taken into consideration when assessing cardiovascular risk and considered a potential target for reducing cardiovascular events. FEV1 and airflow obstruction do not appear to cause increased cardiovascular events; confounding and collider bias may explain previous findings of a causal association.

Lung function, COPD and cognitive function: a multivariable and two sample Mendelian randomization study.

BACKGROUND: Observational studies show an association between reduced lung function and impaired cognition. Cognitive dysfunction influences important health outcomes and is a precursor to dementia, but treatments options are currently very limited. Attention has therefore focused on identifying modifiable risk factors to prevent cognitive decline and preserve cognition. Our objective was to determine if lung function or risk of COPD causes reduced cognitive function using Mendelian randomization (MR). METHODS: Single nucleotide polymorphisms from genome wide association studies of lung function and COPD were used as exposures. We examined their effect on general cognitive function in a sample of 132,452 individuals. We then performed multivariable MR (MVMR), examining the effect of lung function before and after conditioning for covariates. RESULTS: We found only weak evidence that reduced lung function (Beta - 0.002 (SE 0.02), p-value 0.86) or increased liability to COPD (- 0.008 (0.008), p-value 0.35) causes lower cognitive function. MVMR found both reduced FEV1 and FVC do cause lower cognitive function, but that after conditioning for height (- 0.03 (0.03), p-value 0.29 and - 0.01 (0.03) p-value 0.62, for FEV1 and FVC respectively) and educational attainment (- 0.03 (0.03) p-value 0.33 and - 0.01 (0.02), p-value 0.35) the evidence became weak. CONCLUSION: We did not find evidence that reduced lung function or COPD causes reduced cognitive function. Previous observational studies are probably affected by residual confounding. Research efforts should focus on shared risk factors for reduced lung function and cognition, rather than lung function alone as a modifiable risk factor.

Prevalence, risk factors, and clinical implications of preserved ratio impaired spirometry: a UK Biobank cohort analysis.

BACKGROUND: Preserved ratio impaired spirometry (PRISm) is defined as a FEV1 of less than 80% predicted and a FEV1/forced vital capacity (FVC) ratio of 0·70 or higher. Previous research has indicated that PRISm is associated with respiratory symptoms and is a precursor of chronic obstructive pulmonary disease (COPD). However, these findings are based on relatively small selective cohorts with short follow-up. We aimed to determine the prevalence, risk factors, clinical implications, and mortality of PRISm in a large adult general population. METHODS: For this cohort analysis, we used data from the UKBiobank to assess PRISm prevalence, risk factors and associated symptoms, and associated comorbidities in a large adult population. Participants with spirometry deemed acceptable by an investigator (best measure FEV1 and FVC values) at baseline were included. Participants were excluded if they did not have acceptable spirometry or were missing data on body-mass index or smoking status. Control spirometry was defined as a FEV1 of 80% or more predicted and a FEV1/FVC ratio of 0·70 or higher. Airflow obstruction was defined as a FEV1/FVC ratio of less than 0·70. We used multivariable regression to determine risk factors for PRISm and associated comorbidities. Individuals who lived within close proximity to an assessment centre were invited for follow-up, with repeat spirometry. Only participants who had been included at baseline were examined in follow-up. This allowed for a longitudinal analysis of PRISm over time and risk factors for transition to airflow obstruction. We also did the survival analysis for a 12-year period. FINDINGS: Participants were recruited by UK Biobank between Dec 19, 2006, and Oct 10, 2010. We included 351 874 UK Biobank participants (189 247 women and 162 627 men) in our study, with a median follow-up of 9·0 years (IQR 8·0-10·0). 38 639 (11·0%) of 351 874 participants had PRISm at baseline. After adjustment, PRISm was strongly associated with obesity (odds ratio [OR] 2·40 [2·26-2·55], p<0·0001), current smoking (1·48 [1·36-1·62], p<0·0001), and patient reported doctor-diagnosed asthma (1·76 [1·66-1·88], p<0·0001). Other risk factors identified included female sex, being overweight, trunk fat mass, and trunk fat percentage. PRISm was strongly associated with symptoms and comorbidity including increased risk of breathlessness (adjusted OR 2·0 [95% CI 1·91-2·14], p<0·0001) and cardiovascular disease (adjusted OR 1·71 [1·64-1·83], p<0·0001 for heart attack). Longitudinal analysis showed that 241 (12·2%) of 1973 participants who had PRISm at baseline had transitioned to airflow obstruction consistent with COPD. PRISm was associated with increased all-cause mortality (adjusted hazard ratio 1·61 [95% CI 1·53-1·69], p<0·0001) versus control participants. INTERPRETATION: PRISm was associated with breathlessness, multimorbidity, and increased risk of death, which does not seem to be explained by smoking, obesity, or existing lung disease. Although for many patients PRISm is transient, it is important to understand which individuals are at risk of progressive lung function abnormalities. Further research into the genetic, structural and functional pathophysiology of PRISm is warranted. FUNDING: UK Medical Research Council and University of Bristol.