Predicting exacerbations in COPD in the Danish general population

BACKGROUND

Risk of exacerbations in individuals with mild chronic obstructive pulmonary disease (COPD) in the general population is less well described than in more advanced disease. We hypothesized that in addition to history of previous exacerbation also other clinical characteristics predict future moderate exacerbations.

METHODS

In 96,462 individuals in the Copenhagen General Population Study, we identified 3175 with clinical COPD defined as forced expiratory volume in 1 s (FEV1)/forced vital capacity (FVC) < 0.70 and FEV1 <80% predicted in symptomatic individuals without asthma. We estimated the importance of age, sex, FEV1, modified Medical Research Council (mMRC) dyspnea scale, chronic bronchitis, exacerbation history, comorbidities, cohabitation, body mass index, smoking, and blood eosinophils for the 1-year and 3-year future risk of moderate COPD exacerbations and developed a prediction tool for future exacerbations in COPD in the general population based on easily available clinical information.

RESULTS

We observed 265 exacerbations in 2543 maintenance treatment naïve individuals with COPD and 197 exacerbations in 632 individuals with COPD on maintenance treatment. In the maintenance treatment naïve group, exacerbation history (hazard ratio (HR): 8.53), low FEV1 (HR: 4.82 for <30% predicted versus 50-79% predicted), and higher age (HR: 1.46 for ≥75 years versus <65 years) were significant predictors of future exacerbations. In the group on maintenance treatment, male sex and mMRC ≥2 also predicted higher risk with borderline significance.

CONCLUSIONS

In addition to exacerbation history also higher age and lower FEV1 predict future exacerbation risk in COPD in the general population.

Type-2 inflammation and lung function decline in chronic airway disease in the general population

BACKGROUND

It is unclear if type-2 inflammation is associated with accelerated lung function decline in individuals with asthma and chronic obstructive pulmonary disease (COPD). We tested the hypothesis that type-2 inflammation indicated by elevated blood eosinophils (BE) and fraction of exhaled nitric oxide (FeNO) is associated with accelerated lung function decline in the general population.

METHODS

We included adults from the Copenhagen General Population Study with measurements of BE (N=15 605) and FeNO (N=2583) from a follow-up examination and assessed forced expiratory volume in 1 s (FEV1) decline in the preceding 10 years. Based on pre- and post-bronchodilator lung function, smoking history and asthma at follow-up examination, participants were assigned as not having airway disease, asthma with full reversibility (AR), asthma with persistent obstruction (APO), COPD, and not classifiable airflow limitation (NAL).

RESULTS

FEV1 decline in mL/year increased with 1.0 (95% CI 0.6 to 1.4, p<0.0001) per 100 cells/µL higher BE and with 3.2 (95% CI 2.0 to 4.5, p<0.0001) per 10 ppb higher FeNO. Adjusted FEV1 decline in mL/year was 18 (95% CI 17 to 20) in those with BE<300 cells/µL and FeNO<20 ppb, 22 (19-25) in BE≥300 cells/µL or FeNO≥20 ppb, and 27 (21-33) in those with BE≥300 cells/µL and FeNO≥20 ppb (p for trend<0.0001). Corresponding FEV1 declines were 24 (19-29), 33 (25-40) and 44 (31-56) in AR (0.002), 26 (14-37), 36 (12-60) and 56 (24-89) in APO (0.07), 32 (27-36), 31 (24-38) and 44 (24-65) in COPD (0.46), and 27 (21-33), 35 (26-45), and 37 (25-49) in NAL (0.10), respectively.

CONCLUSIONS

Type-2 inflammation indicated by elevated BE and FeNO is associated with accelerated FEV1 decline in individuals with chronic airway disease in the general population, and this association was most pronounced in an asthma-like phenotype.

Plasma adiponectin levels and risk of heart failure, atrial fibrillation, aortic valve stenosis, and myocardial infarction: large-scale observational and Mendelian randomization evidence

AIMS

Adiponectin may play an important protective role in heart failure and associated cardiovascular diseases. We hypothesized that plasma adiponectin is associated observationally and causally, genetically with risk of heart failure, atrial fibrillation, aortic valve stenosis, and myocardial infarction.

METHODS AND RESULTS

In the Copenhagen General Population Study, we examined 30 045 individuals with plasma adiponectin measurements observationally and 96 903 individuals genetically in one-sample Mendelian randomization analyses using five genetic variants explaining 3% of the variation in plasma adiponectin. In the HERMES, UK Biobank, The Nord-Trøndelag Health Study (HUNT), deCODE, the Michigan Genomics Initiative (MGI), DiscovEHR, and the AFGen consortia, we performed two-sample Mendelian randomization analyses in up to 1 030 836 individuals using 12 genetic variants explaining 14% of the variation in plasma adiponectin.In observational analyses modelled linearly, a 1 unit log-transformed higher plasma adiponectin was associated with a hazard ratio of 1.51 (95% confidence interval: 1.37-1.66) for heart failure, 1.63 (1.50-1.78) for atrial fibrillation, 1.21 (1.03-1.41) for aortic valve stenosis, and 1.03 (0.93-1.14) for myocardial infarction; levels above the median were also associated with an increased risk of myocardial infarction, and non-linear U-shaped associations were more apparent for heart failure, aortic valve stenosis, and myocardial infarction in less-adjusted models. Corresponding genetic, causal risk ratios were 0.92 (0.65-1.29), 0.87 (0.68-1.12), 1.55 (0.87-2.76), and 0.93 (0.67-1.30) in one-sample Mendelian randomization analyses, and no significant associations were seen for non-linear one-sample Mendelian randomization analyses; corresponding causal risk ratios were 0.99 (0.89-1.09), 1.00 (0.92-1.08), 1.01 (0.79-1.28), and 0.99 (0.86-1.13) in two-sample Mendelian randomization analyses, respectively.

CONCLUSION

Observationally, elevated plasma adiponectin was associated with an increased risk of heart failure, atrial fibrillation, aortic valve stenosis, and myocardial infarction. However, genetic evidence did not support causality for these associations.

Susceptible Young Adults and Development of COPD Later in Life

RATIONALE

Chronic obstructive pulmonary disease (COPD) has its origin in early life, and the Global Initiative for Chronic Obstructive Lung Disease (GOLD) proposes a pre-disease state "pre-COPD".

OBJECTIVE

We tested the hypothesis that susceptible young adults identified with chronic bronchitis and subtle lung function impairment will develop COPD later in life.

METHODS

We followed random non-obstructive individuals aged 20-50years from two population-based cohorts from different smoking eras, the Copenhagen General Population Study from 2003(N=5497) and Copenhagen City Heart Study from 1976-78(N=2609), for 10 and 25years for development of COPD(forced expiratory volume in one second[FEV1]/forced vital capacity[FVC]<0.70) and COPD GOLD 2-4 (additionally FEV1<80% predicted).

MEASUREMENTS AND MAIN RESULTS

After 10 years follow-up, 28% developed COPD and 13% COPD GOLD 2-4 in individuals susceptible to COPD compared to 8% and 1% in those without any susceptibility to COPD. Correspondingly, after 25years, 22% versus 13% developed COPD and 20% versus 8% developed COPD GOLD 2-4. More than half of incident COPD cases developed from a susceptible state. Compared to those without susceptibility to COPD, multivariable adjusted odds ratios in those susceptible to COPD were 3.42(95% confidence interval:2.78-4.21) for COPD and 10.1(6.77-15.2) for COPD GOLD 2-4 after 10years, and 1.54(1.23-1.93) and 2.12(1.64-2.73) after 25years. The ability of a COPD risk score consisting of the susceptibility state to COPD with smoking and asthma as risk factors to predict COPD later in life was high.

CONCLUSIONS

Our study suggests the existence of a pre-disease state of COPD, which can be used for early identification of susceptible individuals at risk for COPD later in life.

Fraction of exhaled nitric oxide is higher in liver transplant recipients than in controls from the general population: a cohort study

Background

Fraction of exhaled nitric oxide with an expiratory flow of 50 mL/s (FENO50) is a biomarker of eosinophilic airway inflammation. Liver transplant recipients have an increased risk of pulmonary infections, but little is known about the burden of chronic pulmonary diseases in this group. We aimed to assess the prevalence of elevated FENO50 in liver transplant recipients and compare it to controls from the general population.

Methods

FENO50 was measured in 271 liver transplant recipients from The Danish Comorbidity in Liver Transplant Recipients (DACOLT) study and 1,018 age- and sex-matched controls from The Copenhagen General Population Study (CGPS). Elevated FENO50 was defined as ≥25 or ≥50 parts per billion (ppb). The analyses were adjusted for known and suspected confounders.

Results

The median age of the liver transplant recipients was 55 years (interquartile range (IQR) 46-64), and 58% were men. The liver transplant recipients had a higher median FENO50 than the controls [16 ppb (IQR 10-26) vs. 13 ppb (IQR 8-18.), p < 0.001]. Furthermore, the liver transplant recipients had a higher prevalence of elevated FENO50 (for FENO50 ≥25 ppb 27% vs. 11%, p < 0.001 and ≥50 ppb 4% vs. 2%, p = 0.02). The results were similar after adjusting for age, sex, smoking status, use of airway medication, and blood eosinophil counts [the adjusted odds ratio (OR) for FENO50 ≥25 ppb was 3.58 (95% CI: 2.50-5.15, p < 0.0001) and the adjusted OR for FENO50 ≥50 ppb was 3.14 (95% CI: 1.37-7.20, p = 0.007)].

Conclusion

The liver transplant recipients had elevated FENO50, implying increased eosinophilic airway inflammation. The clinical impact of this finding needs further investigation.

Estimating dose-response relationships for vitamin D with coronary heart disease, stroke, and all-cause mortality: observational and Mendelian randomisation analyses

BACKGROUND

Randomised trials of vitamin D supplementation for cardiovascular disease and all-cause mortality have generally reported null findings. However, generalisability of results to individuals with low vitamin D status is unclear. We aimed to characterise dose-response relationships between 25-hydroxyvitamin D (25[OH]D) concentrations and risk of coronary heart disease, stroke, and all-cause mortality in observational and Mendelian randomisation frameworks.

METHODS

Observational analyses were undertaken using data from 33 prospective studies comprising 500 962 individuals with no known history of coronary heart disease or stroke at baseline. Mendelian randomisation analyses were performed in four population-based cohort studies (UK Biobank, EPIC-CVD, and two Copenhagen population-based studies) comprising 386 406 middle-aged individuals of European ancestries, including 33 546 people who developed coronary heart disease, 18 166 people who had a stroke, and 27 885 people who died. Primary outcomes were coronary heart disease, defined as fatal ischaemic heart disease (International Classification of Diseases 10th revision code I20-I25) or non-fatal myocardial infarction (I21-I23); stroke, defined as any cerebrovascular disease (I60-I69); and all-cause mortality.

FINDINGS

Observational analyses suggested inverse associations between incident coronary heart disease, stroke, and all-cause mortality outcomes with 25(OH)D concentration at low 25(OH)D concentrations. In population-wide genetic analyses, there were no associations of genetically predicted 25(OH)D with coronary heart disease (odds ratio [OR] per 10 nmol/L higher genetically-predicted 25(OH)D concentration 0·98, 95% CI 0·95-1·01), stroke (1·01, [0·97-1·05]), or all-cause mortality (0·99, 0·95-1·02). Null findings were also observed in genetic analyses for cause-specific mortality outcomes, and in stratified genetic analyses for all outcomes at all observed levels of 25(OH)D concentrations.

INTERPRETATION

Stratified Mendelian randomisation analyses suggest a lack of causal relationship for 25(OH)D concentrations with both cardiovascular and mortality outcomes for individuals at all levels of 25(OH)D. Our findings suggest that substantial reductions in mortality and cardiovascular morbidity due to long-term low-dose vitamin D supplementation are unlikely even if targeted at individuals with low vitamin D status.

FUNDING

British Heart Foundation, Medical Research Council, National Institute for Health Research, Health Data Research UK, Cancer Research UK, and International Agency for Research on Cancer.

Chronic cough associated with COPD exacerbation, pneumonia and death in the general population

Background

Chronic cough affects up to 10% of the general population and was previously perceived as a comorbidity of underlying conditions, but is nowadays classified as a disease in its own entity that could confer increased risk of morbidity and mortality. We tested the hypothesis that chronic cough is associated with increased risk of COPD exacerbation, pneumonia and all-cause mortality in the general population.

Methods

We identified 2801 individuals with chronic cough, defined as cough lasting >8 weeks, among 44 756 randomly selected individuals from the Copenhagen General Population Study, and recorded COPD exacerbations, pneumonia and all-cause mortality during follow-up.

Results

During up to 5.9 years of follow-up (median 3.4 years), 173 individuals experienced COPD exacerbation, 767 experienced pneumonia and 894 individuals died. Individuals with chronic cough versus those without had cumulative incidences at age 80 years of 12% versus 3% for COPD exacerbation, 30% versus 15% for pneumonia, and 25% versus 13% for death from all causes. After adjustment for age, sex and smoking, individuals with chronic cough versus those without had adjusted hazard ratios of 4.6 (95% CI 2.9-7.2) for COPD exacerbation, 2.2 (1.7-2.7) for pneumonia and 1.7 (1.4-2.0) for all-cause mortality. Among current smokers aged >60 years with airflow limitation, those with versus without chronic cough had an absolute 5-year risk of 10% versus 4% for COPD exacerbation, 16% versus 8% for pneumonia and 19% versus 12% for all-cause mortality.

Conclusion

Chronic cough is associated with higher risks of COPD exacerbation, pneumonia and death, independent of airflow limitation and smoking.

Impact of the metabolic syndrome on cardiopulmonary morbidity and mortality in individuals with lung function impairment: a prospective cohort study of the Danish general population

Background

Whether the metabolic syndrome plays a role for the prognosis of individuals with lung function impairment (preserved ratio impaired spirometry (PRISm) or airflow limitation) is unclear. We hypothesised that the metabolic syndrome in individuals with lung function impairment is associated with increased cardiopulmonary morbidity and mortality.

Methods

The Copenhagen General Population Study was initiated in 2003 based on a random sample of white men and women aged 20-100 years drawn from the Danish general population. The risk of ischemic heart disease/heart failure, respiratory disease, and all-cause mortality was analysed with Cox models adjusted for age, sex, current smoking, and asthma during 15 years of follow-up.

Findings

Among 106,845 adults, 86,159 had normal lung function, 6126 had PRISm, and 14,560 had airflow limitation. We observed 10,448 hospital admissions for ischemic heart disease/heart failure, 21,140 for respiratory disease, and 11,125 deaths. Individuals with versus individuals without the metabolic syndrome generally had higher 5-year absolute risk of all outcomes, including within those with normal lung function, mild-moderate-severe PRISm, and very mild-mild-moderate-severe airflow limitation alike. Compared to individuals without the metabolic syndrome and with normal lung function, those with both the metabolic syndrome and severe PRISm had hazard ratios of 3.74 (95% CI: 2.53-5.55; p < 0.0001) for ischemic heart disease/heart failure, 5.02 (3.85-6.55; p < 0.0001) for respiratory disease, and 5.32 (3.76-7.54; p < 0.0001) for all-cause mortality. Corresponding hazard ratios in those with both the metabolic syndrome and severe airflow limitation were 2.89 (2.34-3.58; p < 0.0001) for ischemic heart disease/heart failure, 5.98 (5.28-6.78; p < 0.0001) for respiratory disease, and 4.16 (3.50-4.95; p < 0.0001) for all-cause mortality, respectively. The metabolic syndrome explained 13% and 27% of the influence of PRISm or airflow limitation on ischemic heart disease/heart failure and all-cause mortality.

Interpretation

The metabolic syndrome conferred increased risk of cardiopulmonary morbidity and mortality at all levels of lung function impairment.

Funding

Danish Lung Foundation, Danish Heart Foundation, Capital Region of Copenhagen, and Boehringer Ingelheim. JV is supported by the NIHR Manchester BRC.

Respiratory muscle strength and pulmonary function in unvaccinated athletes before and after COVID-19 infection: A prospective cohort study

PURPOSE

We investigated abnormalities and recovery in respiratory function after COVID-19 infection in an unvaccinated elite athlete population.

METHODS

Measurements included maximal inspiratory pressure (MIP), maximal expiratory pressure (MEP), forced expiratory volume in 1 s (FEV1), forced vital capacity (FVC), and peak expiratory flow (PEF).

RESULTS

The most frequent reported symptoms were fatigue with 80% and muscle/joint pain and headache with 50%, whereas only 10% reported dyspnoea and 30% cough. During follow-up, MIP was up to 13% and MEP up to 8% lower following COVID-19 infection. Likewise, FEV₁ was up to 2% and FVC up to 5% lower. While MEP and FEV₁ rapidly normalised, MIP and FVC still remained abnormal after 52 days of COVID-19 infection, thereby leading to a restrictive ventilatory pattern. PEF seemed unaffected during follow-up.

CONCLUSIONS

COVID-19 decreases respiratory function in unvaccinated athletes despite reporting few respiratory symptoms and having mild disease. An initiative aimed at reducing the long-term adverse effects following COVID-19 infection seems warranted, which perhaps may be avoided through vaccination.

Nationwide indoor smoking ban and impact on smoking behaviour and lung function: a two-population natural experiment

INTRODUCTION

Many countries have implemented indoor smoking bans over the past two decades. Although smoking bans have been shown to reduce cardiovascular outcomes, little is known about their impact on respiratory health. This study investigated the impact of a nationwide indoor smoking ban on smoking behaviour and lung function.

METHODS

We used repeated cross-sectional data from two large cohorts of the general population comprising 31 807 Swiss and 62 093 Danish adults. We compared associations between smoking ban and smoking prevalence and prebronchodilator lung function trends in Denmark (indoor smoking ban introduced in 2007) and Switzerland (indoor smoking ban introduced in 2010) from 2005 to 2010 using a quasi-experimental study design. We performed difference-in-difference analyses with linear regression models adjusted for age, sex, weight and height.

RESULTS

Denmark had a stronger decrease in active smokers compared with Switzerland. Also, forced expiratory volume in the first second was higher in Danish adults than in Swiss adults: 26 mL (95% CI 2.4 to 49) 1 year, 88 mL (65 to 112) 2 years, and 74 mL (51 to 98) 3 years after smoking ban implementation. Correspondingly, forced vital capacity was higher in Danish adults compared with Swiss adults (80 mL (50 to 109) after 1 year and 126 mL (97 to 155) after two and 3 years). Improvements were observed in both never-smokers and ever-smokers, most pronounced in ever-smokers.

CONCLUSIONS

Nationwide indoor smoking ban is associated with less smoking and improved lung function in the general population. Implementing an indoor smoking ban can improve lung function by influencing smoking behaviour and reducing secondhand smoke.

Faster lung function decline in people living with HIV despite adequate treatment: a longitudinal matched cohort study

INTRODUCTION

Chronic lung disease is common among people living with HIV (PLWH). We hypothesised that PLWH receiving antiretroviral therapy (ART) have faster lung function decline than matched controls.

METHODS

We performed a prospective matched cohort study by including ART-treated PLWH from the Copenhagen Co-morbidity in HIV Infection Study (n=705) and the INSIGHT Strategic Timing of Antiretroviral Treatment Pulmonary Substudy (n=425) and frequency matched population controls from the Copenhagen General Population Study (n=2895) in a 1:3 ratio. Eligible participants were ≥25 years old and had two spirometry tests separated by at least 2 years of follow-up. Forced expiratory volume in 1 s (FEV₁) decline (mL/year) was compared between PLWH and controls using a linear mixed model adjusted for age, sex, ethnicity and smoking status. Effect modification by smoking was investigated in subgroup analyses.

RESULTS

The majority of PLWH were virally suppressed (96.1%). The adjusted mean annual decline in FEV₁ was faster in PLWH than in controls with 36.4 (95% CI 33.7 to 39.1) vs 27.9 (95% CI 26.9 to 28.8) mL/year, yielding a difference of 8.5 (95% CI 5.6 to 11.4) mL/year. The association between HIV and FEV₁ decline was modified by smoking, with the largest difference in current smokers (difference: 16.8 (95% CI 10.5 to 23.0) mL/year) and the smallest difference in never-smokers (difference: 5.0 (95% CI 0.7 to 9.3) mL/year). FEV₁ decline >40 mL/year was more prevalent in PLWH (adjusted OR: 1.98 (95% CI 1.67 to 2.34)).

CONCLUSION

Well-treated PLWH have faster lung function decline than controls and smoking seems to modify this association, suggesting that smoking may lead to more rapid lung function decline in PLWH than in controls.

Clonal haematopoiesis of indeterminate potential and impaired kidney function-A Danish general population study with 11 years follow-up

The myeloproliferative neoplasms are associated with chronic kidney disease but whether clonal haematopoiesis of indeterminate potential (CHIP) is associated with impaired kidney function is unknown. In the Danish General Suburban Population Study (N = 19 958) from 2010 to 2013, 645 individuals were positive for JAK2V617F (N = 613) or CALR (N = 32) mutations. Mutation-positive individuals without haematological malignancy were defined as having CHIP (N = 629). We used multiple and inverse probability weighted (IPW)-adjusted linear regression analysis to estimate adjusted mean (95% confidence interval) differences in estimated glomerular filtration rate (eGFR; ml/min/1.73 m² ) by mutation status, variant allele frequency (VAF%), blood cell counts, and neutrophil-to-lymphocyte ratio (NLR). We performed 11-year longitudinal follow-up of eGFR in all individuals. Compared to CHIP-negative individuals, the mean differences in eGFR were -5.6 (-10.3, -0.8, p = .02) for CALR, -11.9 (-21.4, -2.4, p = 0.01) for CALR type 2, and -10.1 (-18.1, -2.2, p = .01) for CALR with VAF ≥ 1%. The IPW-adjusted linear regression analyses showed similar results. NLR was negatively associated with eGFR. Individuals with CALR type 2 had a worse 11-year longitudinal follow-up on eGFR compared to CHIP-negative individuals (p = .004). In conclusion, individuals with CALR mutations, especially CALR type 2, had impaired kidney function compared to CHIP-negative individuals as measured by a lower eGFR at baseline and during 11-year follow-up.

Prognosis of Patients with Chronic Obstructive Pulmonary Disease Not Eligible for Major Clinical Trials

Rationale: Randomized controlled trials only include a subset of patients with chronic obstructive pulmonary disease (COPD) fulfilling strict inclusion criteria. Thus, most patients with COPD in a real-world setting do not have the necessary evidence to support treatment effectiveness. Objectives: To test the hypotheses that most individuals with COPD in the general population are not represented in major clinical trials despite clinically significant disease with exacerbations and early death. Methods: In 105,630 adults from a Danish contemporary population-based cohort, we defined COPD as age 40 or more years, chronic respiratory symptoms, history of smoking exposure, and airflow limitation with FEV₁/FVC < 0.70. Outcomes included acute exacerbations and all-cause mortality. Symptomatic smokers without COPD were used as a reference group. Measurements and Main Results: Of all, 7,516 (7%) and 16,079 (15%) were symptomatic smokers with and without COPD. Only 44% of those with COPD were eligible for major clinical trials when applying FEV₁ < 80% predicted, smoking history of 10 or more pack-years, and no comorbid asthma as common inclusion criteria. During the median 8.9 years of follow-up, we observed 2,130 acute exacerbations and 3,973 deaths in symptomatic smokers. Compared with symptomatic smokers without COPD, multivariable-adjusted hazard ratios for exacerbations were 7.45 (95% confidence interval, 5.41-10.3) and 29.0 (21.1-39.8) in those with COPD, respectively, excluded and eligible for clinical trials. Corresponding hazard ratios for all-cause mortality were 1.21 (1.11-1.31) and 1.67 (1.54-1.81), respectively. Conclusions: More than half of individuals with COPD in the general population are excluded from major clinical trials; however, these individuals have a clinically significant disease with exacerbations and early death compared with symptomatic smokers without COPD.

Plasma immunoglobulin E and risk of exacerbation and mortality in chronic obstructive pulmonary disease: A contemporary population-based cohort

BACKGROUND

Novel biomarkers and targeted treatments are needed for patients with chronic obstructive pulmonary disease (COPD).

OBJECTIVE

To test the hypothesis that high plasma immunoglobulin (Ig)E concentrations associate with increased risk of exacerbation and mortality in individuals with COPD in the general population.

METHODS

Among 46,598 adults in the Copenhagen General Population Study, we included 1559 with COPD, defined as forced expiratory volume in 1 second/forced vital capacity < 0.70 and forced expiratory volume in 1 second < 80% predicted in individuals aged ≥ 40 years with chronic respiratory symptoms and smoking exposure ≥ 10 pack-years, and without asthma. We assessed risk of future severe exacerbation and all-cause mortality according to baseline plasma IgE ≥ 76 IU/mL, a clinical cutoff for omalizumab treatment in severe asthma.

RESULTS

During 14 years of follow-up (median, 6.9; interquartile range, 3.4), we recorded 224 severe exacerbations and 434 deaths in 1559 individuals with COPD. Individuals with COPD with IgE ≥ 76 IU/mL vs those with < 76 IU/mL had a multivariable adjusted hazard ratio (HR) of 1.43 (95% confidence interval, 1.07-1.89) for severe exacerbation and 1.30 (1.05-1.62) for all-cause mortality. Compared with individuals with IgE < 76 IU/mL and blood eosinophils < 300 cells/µL, the multivariable adjusted HR for severe exacerbation was 1.12 (0.76-1.67) for those with IgE < 76 IU/mL and blood eosinophils ≥ 300 cells/µL, 1.62 (1.17-2.24) for IgE ≥ 76 IU/mL and blood eosinophils < 300 cells/µL, and 1.06 (0.63-1.77) for those with IgE ≥ 76 IU/mL and blood eosinophils ≥ 300 cells/µL. Corresponding HRs for all-cause mortality were 1.27 (0.99-1.63), 1.47 (1.14-1.88), and 1.17 (0.83-1.64), respectively.

CONCLUSION

High plasma IgE was associated with an increased risk of severe exacerbation and all-cause mortality in individuals with COPD in the general population, independent of blood eosinophils.

Plasma adiponectin and risk of asthma: observational analysis, genetic Mendelian randomisation and meta-analysis

BACKGROUND

Adiponectin, an adipocyte-secreted protein-hormone with inflammatory properties, has a potentially important role in the development and progression of asthma. Unravelling whether adiponectin is a causal risk factor for asthma is an important issue to clarify as adiponectin could be a potential novel drug target for the treatment of asthma.

OBJECTIVE

We tested the hypothesis that plasma adiponectin is associated observationally and causally (using genetic variants as instrumental variables) with risk of asthma.

METHODS

In the Copenhagen General Population Study, we did an observational analysis in 28 845 individuals (2278 asthma cases) with plasma adiponectin measurements, and a genetic one-sample Mendelian randomisation analysis in 94 868 individuals (7128 asthma cases) with 4 genetic variants. Furthermore, in the UK Biobank, we did a genetic two-sample Mendelian randomisation analysis in 462 933 individuals (53 598 asthma cases) with 12 genetic variants. Lastly, we meta-analysed the genetic findings.

RESULTS

While a 1 unit log-transformed higher plasma adiponectin in the Copenhagen General Population Study was associated with an observational OR of 1.65 (95% CI 1.29 to 2.08) for asthma, the corresponding genetic causal OR was 1.03 (95% CI 0.75 to 1.42). The genetic causal OR for asthma in the UK Biobank was 1.00 (95% CI 0.99 to 1.00). Lastly, genetic meta-analysis confirmed lack of association between genetically high plasma adiponectin and causal OR for asthma.

CONCLUSION

Observationally, high plasma adiponectin is associated with increased risk of asthma; however, genetic evidence could not support a causal association between plasma adiponectin and asthma.

Estimating dose-response relationships for vitamin D with coronary heart disease, stroke, and all-cause mortality: observational and Mendelian randomisation analyses

BACKGROUND

Randomised trials of vitamin D supplementation for cardiovascular disease and all-cause mortality have generally reported null findings. However, generalisability of results to individuals with low vitamin D status is unclear. We aimed to characterise dose-response relationships between 25-hydroxyvitamin D (25[OH]D) concentrations and risk of coronary heart disease, stroke, and all-cause mortality in observational and Mendelian randomisation frameworks.

METHODS

Observational analyses were undertaken using data from 33 prospective studies comprising 500 962 individuals with no known history of coronary heart disease or stroke at baseline. Mendelian randomisation analyses were performed in four population-based cohort studies (UK Biobank, EPIC-CVD, and two Copenhagen population-based studies) comprising 386 406 middle-aged individuals of European ancestries, including 33 546 people who developed coronary heart disease, 18 166 people who had a stroke, and 27 885 people who died. Primary outcomes were coronary heart disease, defined as fatal ischaemic heart disease (International Classification of Diseases 10th revision code I20-I25) or non-fatal myocardial infarction (I21-I23); stroke, defined as any cerebrovascular disease (I60-I69); and all-cause mortality.

FINDINGS

Observational analyses suggested inverse associations between incident coronary heart disease, stroke, and all-cause mortality outcomes with 25(OH)D concentration at low 25(OH)D concentrations. In population-wide genetic analyses, there were no associations of genetically-predicted 25(OH)D with coronary heart disease, stroke, or all-cause mortality. However, for the participants with vitamin D deficiency (25[OH]D concentration <25 nmol/L), genetic analyses provided strong evidence for an inverse association with all-cause mortality (odds ratio [OR] per 10 nmol/L increase in genetically-predicted 25[OH]D concentration 0·69 [95% CI 0·59-0·80]; p<0·0001) and non-significant inverse associations for stroke (0·85 [0·70-1·02], p=0·09) and coronary heart disease (0·89 [0·76-1·04]; p=0·14). A finer stratification of participants found inverse associations between genetically-predicted 25(OH)D concentrations and all-cause mortality up to around 40 nmol/L.

INTERPRETATION

Stratified Mendelian randomisation analyses suggest a causal relationship between 25(OH)D concentrations and mortality for individuals with low vitamin D status. Our findings have implications for the design of vitamin D supplementation trials, and potential disease prevention strategies.

FUNDING

British Heart Foundation, Medical Research Council, National Institute for Health Research, Health Data Research UK, Cancer Research UK, and International Agency for Research on Cancer.

Low Plasma Adiponectin in Risk of Type 2 Diabetes: Observational Analysis and One- and Two-Sample Mendelian Randomization Analyses in 756,219 Individuals

We tested the hypothesis that low plasma adiponectin is associated observationally and causally with increased risk of type 2 diabetes. Observational analyses are prone to confounding and reverse causation, while genetic Mendelian randomization (MR) analyses are much less influenced by these biases. We examined 30,045 individuals from the Copenhagen General Population Study observationally (plasma adiponectin [1,751 individuals with type 2 diabetes]), 96,903 Copenhagen individuals using one-sample MR (5 genetic variants [5,012 individuals with type 2 diabetes]), and 659,316 Europeans (ADIPOGen, GERA, DIAGRAM, UK Biobank) using two-sample MR (10 genetic variants [62,892 individuals type 2 diabetes]). Observationally, and in comparisons with individuals with median plasma adiponectin of 28.9 μg/mL (4th quartile), multivariable adjusted hazard ratios (HRs) for type 2 diabetes were 1.42 (95% CI 1.18-1.72) for 19.2 μg/mL (3rd quartile), 2.21 (1.84-2.66) for 13.9 μg/mL (2nd quartile), and 4.05 (3.38-4.86) for 9.2 μg/mL (1st quartile). Corresponding cumulative incidence for type 2 diabetes at age 70 years was 3%, 7%, 11%, and 20%, respectively. A 1 μg/mL lower plasma adiponectin conferred an HR for type 2 diabetes of 1.07 (1.06-1.09), while genetic, causal risk ratio per 1 unit log-transformed lower plasma adiponectin was 1.13 (95% CI 0.83-1.53) in one-sample MR and 1.26 (1.01-1.57) in two-sample MR. In conclusion, low plasma adiponectin is associated with increased risk of type 2 diabetes, an association that could represent a causal relationship.

Changes in lung function in European adults born between 1884 and 1996 and implications for the diagnosis of lung disease: a cross-sectional analysis of ten population-based studies

BACKGROUND

During the past century, socioeconomic and scientific advances have resulted in changes in the health and physique of European populations. Accompanying improvements in lung function, if unrecognised, could result in the misclassification of lung function measurements and misdiagnosis of lung diseases. We therefore investigated changes in population lung function with birth year across the past century, accounting for increasing population height, and examined how such changes might influence the interpretation of lung function measurements.

METHODS

In our analyses of cross-sectional data from ten European population-based studies, we included individuals aged 20-94 years who were born between 1884 and 1996, regardless of previous respiratory diagnoses or symptoms. FEV₁, forced vital capacity (FVC), height, weight, and smoking behaviour were measured between 1965 and 2016. We used meta-regression to investigate how FEV₁ and FVC (adjusting for age, study, height, sex, smoking status, smoking pack-years, and weight) and the FEV₁/FVC ratio (adjusting for age, study, sex, and smoking status) changed with birth year. Using estimates from these models, we graphically explored how mean lung function values would be expected to progressively deviate from predicted values. To substantiate our findings, we used linear regression to investigate how the FEV₁ and FVC values predicted by 32 reference equations published between 1961 and 2015 changed with estimated birth year.

FINDINGS

Across the ten included studies, we included 243 465 European participants (mean age 51·4 years, 95% CI 51·4-51·5) in our analysis, of whom 136 275 (56·0%) were female and 107 190 (44·0%) were male. After full adjustment, FEV₁ increased by 4·8 mL/birth year (95% CI 2·6-7·0; p<0·0001) and FVC increased by 8·8 mL/birth year (5·7-12·0; p<0·0001). Birth year-related increases in the FEV₁ and FVC values predicted by published reference equations corroborated these findings. This height-independent increase in FEV₁ and FVC across the last century will have caused mean population values to progressively exceed previously predicted values. However, the population mean adjusted FEV₁/FVC ratio decreased by 0·11 per 100 birth years (95% CI 0·09-0·14; p<0·0001).

INTERPRETATION

If current diagnostic criteria remain unchanged, the identified shifts in European values will allow the easier fulfilment of diagnostic criteria for lung diseases such as chronic obstructive pulmonary disease, but the systematic underestimation of lung disease severity.

FUNDING

The European Respiratory Society, AstraZeneca, Chiesi Farmaceutici, GlaxoSmithKline, Menarini, and Sanofi-Genzyme.

Importance of Early COPD in Young Adults for Development of Clinical COPD: Findings from the Copenhagen General Population Study

Rationale: Individuals who will develop chronic obstructive pulmonary disease (COPD) could be identified at an early age before clinical manifestations appear. Objectives: We investigated risk of clinical COPD 10 years later in young adults from the general population with and without early COPD with a focus on smoking exposure. Methods: We included 14,870 individuals aged 20-100 years from the Copenhagen General Population Study with spirometry 10 years apart. Early COPD was defined as baseline FEV₁/FVC less than the lower limit of normal in individuals aged <50 years. Outcomes included clinical COPD at final examination 10 years later (chronic respiratory symptoms with FEV₁/FVC <0.70 and FEV₁ <80% predicted) and acute exacerbation hospitalizations during follow-up. Measurements and Main Results: Among 5,497 individuals aged <50 years at baseline with FEV₁/FVC ≥0.70, 104 (3%) developed clinical COPD 10 years later; 4% of smokers with ≥10 pack-years had early COPD; 3% of smokers with <10 pack-years had early COPD; and 2% of never-smokers had early COPD. Among smokers with ≥10 pack-years, 24% developed clinical COPD in those with early COPD versus 4% in those without early COPD. Corresponding numbers were 10% and 1% in smokers with <10 pack-years and 3% and <1% in never-smokers, respectively. Among individuals with early COPD, odds ratios for clinical COPD 10 years later were 7.77 (95% confidence interval [CI], 4.10-14.7) in smokers with ≥10 pack-years and 8.56 (95% CI, 4.92-14.9) in all smokers, whereas hazard ratios for acute exacerbation hospitalizations were 4.16 (95% CI, 1.66-10.5) and 4.33 (95% CI, 1.89-9.93), respectively. Results were validated in the Copenhagen City Heart Study. Conclusions: Depending on amount of smoking exposure, <24% of young adults in the general population with early COPD develop clinical COPD 10 years later. A smoking exposure threshold for early COPD should be reconsidered, as younger individuals are less represented in those with high smoking exposure.

Trajectory of Preserved Ratio Impaired Spirometry: Natural History and Long-Term Prognosis

RATIONALE

Natural history of Preserved Ratio Impaired Spirometry (PRISm), often defined as FEV1/FVC≥lower limit of normal and FEV1<80% of predicted value, is not well-described.

OBJECTIVE

To investigate natural history and long-term prognosis of PRISm trajectories: persistent PRISm trajectory (individuals with PRISm both as young and as middle-aged); normal-to-PRISm trajectory (individuals developing PRISm from normal spirometry in young adulthood); and PRISm-to-normal trajectory (individuals recovering from PRISm in young adulthood by normalizing spirometry while middle-aged).

METHODS

We followed 1160 individuals aged 20-40 years from the Copenhagen City Heart Study from 1976-83 until 2001-03 to determine their lung function trajectory: 72 had persistent PRISm trajectory, 76 normal-to-PRISm trajectory, 155 PRISm-to-normal trajectory, and 857 had normal trajectory. From 2001-03 until 2018, we determined risk of cardiopulmonary disease and death.

MEASUREMENTS AND MAIN RESULTS

We recorded 198 admissions for heart disease, 143 for pneumonia, and 64 for COPD, and 171 deaths. Compared to individuals with normal trajectory, hazards ratios for individuals with persistent PRISm trajectory were 1.55 (95% CI, 0.91-2.65) for heart disease admission, 2.86 (1.70-4.83) for pneumonia admission, 6.57 (3.41-12.66) for COPD admission, and 3.68 (2.38-5.68) for all-cause mortality. Corresponding hazards ratios for individuals with normal-to-PRISm trajectory were 1.91 (1.24-2.95), 2.74 (1.70-4.42), 6.03 (3.41-10.64), and 2.96 (1.94-4.51), respectively. Prognosis of individuals with PRISm-to-normal trajectory did not differ from those with normal trajectory.

CONCLUSIONS

PRISm in middle-aged individuals is associated with increased risk of cardiopulmonary disease and all-cause mortality, but individuals who recover from PRISm during their adult life are no longer at increased risk.

Risk and impact of chronic cough in obese individuals from the general population

BACKGROUND

Obese individuals may be at higher risk of chronic cough. We investigated the risk and impact of chronic cough in obese individuals from the general population.

METHODS

We recorded chronic cough, body mass index (BMI) and other related clinical conditions in 44 554 adults from the Copenhagen General Population Study. Individuals with asthma and/or chronic obstructive pulmonary disease were excluded (n=10 977). BMI was divided into: underweight (BMI <18.5 kg/m²), normal weight (18.5-24.9 kg/m²), overweight (25.0-29.9 kg/m²), obese (30.0-34.9 kg/m²) and severely obese (≥35.0 kg/m²).

RESULTS

Among 33 577 adults from the general population, 27 829 (83%) were non-obese and 5748 (17%) were obese. Compared with individuals with normal weight, multivariable adjusted ORs for chronic cough risk were 1.4 (95% CI 1.2 to 1.6) in overweight, 1.9 (95% CI 1.7 to 2.2) in obese and 2.6 (95% CI 2.1 to 3.2) in severely obese individuals. Mediation analyses showed that chronic cough due to obesity was up to 23% mediated by gastro-oesophageal reflux disease (GERD). Other mediators included low vegetable intake with 10% and occupational exposure with 8%. Among obese individuals, those with versus without chronic cough had worse accompanying respiratory symptoms, more often comorbidities including GERD and diabetes, greater healthcare utilisations, lower lung function and higher blood inflammation (all p<0.05).

CONCLUSION

There is dose-response relationship between BMI and chronic cough, and chronic cough risk is twofold to threefold higher in obese individuals from the general population. This increased risk was partly mediated by GERD, low vegetable intake and occupational exposure, supporting that there may be benefit to gain by ameliorating some of these factors in obese individuals with chronic cough.

Supernormal lung function and risk of COPD: A contemporary population-based cohort study

BACKGROUND

Investigation of the natural history of chronic obstructive pulmonary disease (COPD) has led to the recognition that individuals with higher than normal lung function may have lower risk of developing COPD. We tested the hypothesis that individuals with supernormal lung function have lower risk of COPD.

METHODS

We followed 108,246 adults from the Copenhagen General Population Study recruited between 2003 and 2015 for clinical COPD outcomes until 2018. A subset of 16,892 attended another examination approximately 10 years later, allowing to investigate lung function decline and COPD development (forced expiratory volume in 1 se (FEV₁)/forced vital capacity (FVC)<0·70 and FEV₁<80% predicted with chronic respiratory symptom). Supernormal lung function was defined as FEV₁>upper limit of normal (ULN).

FINDINGS

At baseline, 3944(4%) had supernormal lung function, 91,938(85%) normal lung function, and 12,364(11%) had below normal lung function. Individuals with baseline supernormal versus normal lung function had higher FEV₁ decline but did not differ in FEV₁/FVC decline. None had COPD at 10 years in those with supernormal lung function, while 3% had in those with normal lung function. Early-life risk factors associated with COPD development and smoking exposure in different stages of life were less common in individuals with supernormal lung function. Compared to individuals with normal lung function, multivariable adjusted hazard ratios in those with supernormal lung function were 0·19(95% confidence interval:0·08-0·46) for acute obstructive lung disease hospitalisations, 0·56(0·45-0·69) for pneumonia hospitalisations, and 0·81(0·72-0·91) for all-cause mortality.

INTERPRETATION

Supernormal lung function is associated with lower risk of developing COPD.

FUNDING

Herlev and Gentofte Hospital and Lundbeck Foundation.

Risk of ulcerative colitis and Crohn's disease in smokers lacks causal evidence

Smoking has been associated with opposing risks of ulcerative colitis and Crohn's disease. Whether these observational associations reflect actual causal associations, confounding, or reverse causation is unclear. Using a Mendelian randomization approach, we tested the hypothesis that smoking protects against ulcerative colitis and is a cause of Crohn's disease. We included 118,683 white Danes aged ≥ 20 from the Copenhagen General Population Study (2003-2015) and the Copenhagen City Heart Study (1991-94 and 2001-03). During follow-up until 2018, we investigated the association of smoking and CHRNA3 rs1051730, where the T-allele is strongly associated with nicotine dependence, with risk of ulcerative colitis and Crohn's disease. We identified 1312 cases of ulcerative colitis and 671 cases of Crohn's disease. Compared to never-smokers, multivariable adjusted hazard ratios (HRs) for ulcerative colitis were 1.69(95% confidence interval [CI] 1.32-2.15) in former smokers and 2.27(1.74-2.96) in current smokers. Corresponding HRs for Crohn's disease were 1.31(0.93-1.84) and 1.93(1.34-2.78), respectively. Among ever-smokers when compared to non-carriers of the CHRNA3 rs1051730 T-allele, age and sex adjusted HRs for risk of ulcerative colitis were 1.03(95%CI 0.89-1.18) in heterozygotes and 0.91(0.72-1.16) in homozygotes. Corresponding HRs for Crohn's disease were 1.05(0.87-1.28) and 1.02(0.74-1.41), respectively. In a meta-analysis combined with UK Biobank, there was no evidence that CHRNA3 rs1051730 was associated with risk of ulcerative colitis or Crohn's disease. In conclusion, current versus never-smoking was associated with unexpected 2.3-fold risk of ulcerative colitis and expected 1.9-fold risk of Crohn's disease in prospective analyses; however, genetic evidence of lifelong increased smoking intensity did not support causal relationships.

Fraction of Exhaled Nitric Oxide Levels Are Elevated in People Living With Human Immunodeficiency Virus Compared to Uninfected Controls, Suggesting Increased Eosinophilic Airway Inflammation

BACKGROUND

Increased risk of asthma and chronic obstructive pulmonary disease has been reported in people living with human immunodeficiency virus (PLWH). Fraction of exhaled nitric oxide (FeNO) is a marker of eosinophilic airway inflammation. We assessed FeNO levels in PLWH and matched uninfected controls and investigated whether human immunodeficiency virus (HIV) status is independently associated with elevated FeNO.

METHODS

FeNO was quantified by NIOX Vero and pulmonary function was assessed by spirometry in 432 PLWH from the Copenhagen Comorbidity in HIV Infection Study and in 1618 age- and sex-matched uninfected controls from the Copenhagen General Population Study. Elevated FeNO was defined as ≥25 parts per billion. Associations between FeNO and HIV status were adjusted for known potential confounders.

RESULTS

Mean age of PLWH was 50.7 (standard deviation [SD], 11.1) years and 97.4% received combination antiretroviral therapy. PLWH had higher FeNO than uninfected controls (median, 17.0 [interquartile range {IQR}, 11.0-26.0] vs 13.0 [IQR, 9.0-19.0]; P < .001). Also, PLWH had a higher prevalence of elevated FeNO than uninfected controls (27.5% vs 12.3%; P < .001). This association remained after adjusting for age, sex, height, smoking status, use of airway medication, blood eosinophils, and immunoglobulin E (adjusted OR [aOR], 3.56 [95% CI, 2.51-5.04]; P < .001). Elevated FeNO was associated with self-reported asthma (aOR, 2.65 [95% CI, 1.66-4.24]; P < .001) but not with airflow limitation (aOR, 1.07 [95% CI, .71-1.62]; P = .745).

CONCLUSIONS

HIV status was independently associated with elevated FeNO, suggesting increased eosinophilic airway inflammation. The potential impact on chronic lung disease pathogenesis needs further investigation.

Causal Relationship between Plasma Adiponectin and Body Mass Index: One- and Two-Sample Bidirectional Mendelian Randomization Analyses in 460 397 Individuals

BACKGROUND

Adiponectin is a protein hormone produced by adipocytes that may play an important role in obesity. However, the causal interrelation between plasma adiponectin and body mass index (BMI) is still uncertain. We tested the hypotheses that (a) plasma adiponectin and BMI are inversely associated observationally, (b) genetically high BMI is associated with lower plasma adiponectin, and (c) genetically high plasma adiponectin is associated with lower BMI.

METHODS

Information on 108 896 individuals from the Copenhagen General Population Study was used in observational and bidirectional one-sample Mendelian randomization analyses, using 5 genetic variants for BMI and 3 for adiponectin. For independent confirmation, information on 322 154 individuals from the GIANT consortium, and 29 347 individuals from the ADIPOGen consortium was used in bidirectional two-sample Mendelian randomization analysis, using 68 genetic variants for BMI and 14 for adiponectin.

RESULTS

In observational analyses, a 1 kg/m2 increase in BMI was associated with -0.44 µg/mL (95% confidence interval: -0.46, -0.42) in plasma adiponectin, whereas a 1 µg/mL increase in plasma adiponectin was associated with -0.11 kg/m2 (-0.12, -0.11) in BMI. In causal genetic analyses, no associations were observed between BMI and plasma adiponectin and vice versa. In one-sample Mendelian randomization analyses, a 1 kg/m2 genetically determined increase in BMI was associated with -0.13 µg/mL (-0.53, 0.28) in plasma adiponectin, whereas a 1 µg/mL genetically determined increase in plasma adiponectin was associated with 0.01 kg/m2 (-0.05, 0.07) in BMI. Corresponding estimates in the two-sample Mendelian randomization analyses were 0.03 µg/mL (-0.02, 0.07) and 0.03 kg/m2(-0.02, 0.07), respectively.

CONCLUSIONS

Observationally, plasma adiponectin and BMI are inversely associated. In contrast, genetically high plasma adiponectin is unlikely to influence BMI, and genetically high BMI is unlikely to influence plasma adiponectin.

Low vitamin D and risk of bacterial pneumonias: Mendelian randomisation studies in two population-based cohorts

BACKGROUND

Vitamin D may regulate the innate immune system, and randomised controlled trials suggest a beneficial effect of vitamin D supplementation against acute respiratory tract infections. By using a Mendelian randomisation approach, we tested the hypothesis that low 25-hydroxyvitamin D is associated with increased risk of bacterial pneumonia in observational and genetic analyses.

METHODS

We genotyped 116 335 randomly chosen white Danes aged 20 to 100 from the Copenhagen City Heart Study and Copenhagen General Population Study for plasma 25-hydroxyvitamin D decreasing genetic variants around CYP2R1 (rs117913124, rs12794714 and rs10741657), DHCR7 (rs7944926 and rs11234027), GEMIN2 (rs2277458) and HAL (rs3819817). Information on plasma 25-hydroxyvitamin D was available on 35 833 individuals. Individuals were followed from 1981 through 2018 for hospital diagnoses of bacterial pneumonias.

RESULTS

During up to 38 years follow-up, we observed 6342 bacterial pneumonias in observational analyses and 13 916 in genetic analyses. In observational analyses, multivariable adjusted HR for bacterial pneumonias was 1.27 (95% CI: 1.16 to 1.40) for individuals with 25-hydroxyvitamin D<25 nmol/L compared with those with ≥25 nmol/L. In genetic analyses, the OR for bacterial pneumonia per 10 nmol/L lower plasma 25-hydroxyvitamin D was 1.12 (95% CI: 1.02 to 1.23) in Wald's ratio, 1.12 (95% CI: 1.04 to 1.20) in inverse-variance weighted, 1.63 (95% CI: 0.96 to 2.78) in MR-Egger and 1.15 (95% CI: 1.05 to 1.26) in weighted median instrumental variable analysis. This association was strongest for genetic variants around CYP2R1. There was no observational or genetic evidence to support that 25-hydroxyvitamin D is associated with risk of urinary tract infections, skin infections, sepsis or gastroenteritis, which were used as negative control outcomes.

CONCLUSIONS

Low vitamin D is associated observationally and genetically with increased risk of bacterial pneumonias.

Lung Function Trajectories Leading to Chronic Obstructive Pulmonary Disease as Predictors of Exacerbations and Mortality

Rationale: Chronic obstructive pulmonary disease (COPD) can develop not only through a lung function trajectory dominated by an accelerated decline of FEV₁ from normal maximally attained FEV₁ in early adulthood (normal maximally attained FEV₁ trajectory) but also through a trajectory with FEV₁ below normal in early adulthood (low maximally attained FEV₁ trajectory).Objectives: To test whether the long-term risk of exacerbations and mortality differs between these two subtypes of COPD.Methods: The cohort included 1,170 young adults enrolled in the Copenhagen City Heart Study during the 1970s and 1980s. In 2001-2003, which served as the baseline for the present analyses, 79 participants had developed COPD through normal maximally attained FEV₁ trajectory, 65 had developed COPD through low maximally attained FEV₁ trajectory, and 1,026 did not have COPD.Measurements and Main Results: From 2001 until 2018, we observed 139 severe exacerbations of COPD and 215 deaths, of which 55 were due to nonmalignant respiratory disease. In Cox models, there was no difference with regard to risk of severe exacerbations between the two trajectories, but individuals with normal maximally attained FEV₁ had an increased risk of nonmalignant respiratory disease mortality (using inverse probability of censoring weighting with adjusted hazard ratio [HR], 6.20; 95% confidence interval [CI], 2.09-18.37; P = 0.001) and all-cause mortality (adjusted HR, 1.93; 95% CI, 1.14-3.26; P = 0.01) compared with individuals with low maximally attained FEV₁.Conclusions: COPD developed through normal maximally attained FEV₁ trajectory is associated with an increased risk of respiratory and all-cause mortality compared with COPD developed through low maximally attained FEV₁ trajectory.

Comparison of five major airflow limitation criteria to identify high-risk individuals with COPD: a contemporary population-based cohort

Background

Different airflow limitation criteria are often used to diagnose COPD. We investigated head-to-head whether Global Initiative for Chronic Obstructive Lung Disease (GOLD) (FEV1/FVC <0.70) and four lower limit of normal (LLN) (FEV1/FVC <LLN) criteria to diagnose airflow limitation differ in identifying individuals at risk of COPD exacerbations and mortality.

Methods

108 246 individuals aged 20–100 years randomly selected from the general population were followed from 2003 through 2018 to determine risk of COPD exacerbations, respiratory mortality and all-cause mortality. LLN criteria used equations from Global Lung Initiative (GLI), National Health and Nutrition Examination Survey (NHANES), European Community for Steel and Coal (ECSC) and Copenhagen City Heart Study (CCHS)/Copenhagen General Population Study (CGPS).

Results

Prevalence of airflow limitation was 17% for GOLD, 8.6% for GLI, 10% for NHANES, 8.2% for ECSC and 14% for CCHS/CGPS. During 14.4 years follow-up, we observed 2745 COPD exacerbations, 762 respiratory deaths and 10 338 all-cause deaths. Comparing individuals with versus without airflow limitation, HRs for COPD exacerbations were 17 (95% CI 14 to 20) for GOLD, 21 (18 to 24) for GLI, 20 (17 to 23) for NHANES, 21 (18 to 24) for ECSC and 18 (16 to 21) for CCHS/CGPS. Corresponding HRs for respiratory mortality were 3.7 (3.1 to 4.3), 6.4 (5.6 to 7.5), 5.7 (4.9 to 6.6), 6.2 (5.3 to 7.2) and 4.5 (3.9 to 5.2), and for all-cause mortality 1.5 (1.4 to 1.5), 1.9 (1.8 to 2.0), 1.8 (1.7 to 1.9), 1.9 (1.8 to 2.0) and 1.7 (1.6 to 1.7), respectively. Differences in Harrell’s C were minute for these outcomes; nonetheless, Harrell’s C was slightly higher for LLN criteria compared with GOLD for mortality outcomes.

Conclusions

The prevalence of airflow limitation ranged from 8% to 17% using GOLD and four different LLN criteria; however, identified individuals with the five different criteria had similar risk of COPD exacerbations and mortality.

Smoking Reduces Plasma Bilirubin: Observational and Genetic Analyses in the Copenhagen General Population Study

INTRODUCTION

Observational studies have found lower concentrations of plasma bilirubin in current smokers compared with former and never smokers. However, whether there is a causal relationship between smoking and bilirubin is unknown. In a Mendelian randomization analysis, we tested the hypothesis that higher tobacco consumption is causally associated with lower concentrations of plasma bilirubin.

METHODS

We genotyped 103 557 individuals aged 20-100 years from the Copenhagen General Population Study for the CHRNA3 rs1051730 genotype, known to be associated with higher tobacco consumption. Tobacco consumption was defined as daily and cumulative tobacco consumption.

RESULTS

In observational multivariable-adjusted analyses, a 10 g/day higher daily tobacco consumption was associated with a 0.28 µmol/L (95% confidence interval = 0.20 to 0.35) lower concentration of plasma bilirubin in current smokers, and a 10 pack-year higher cumulative tobacco consumption was associated with a 0.19 µmol/L (0.17 to 0.21) lower concentration of plasma bilirubin in former and current smokers. Using the CHRNA3 rs1051730 genotype as a proxy for daily and cumulative tobacco consumption, the difference in plasma bilirubin per T-allele was -0.12 µmol/L (-0.23 to -0.002) in current smokers and -0.09 µmol/L (-0.15 to -0.01) in current and former smokers combined. Furthermore, observationally bilirubin concentrations increased with time from smoking cessation in former smokers.

CONCLUSION

Higher daily and cumulative tobacco consumption were associated with lower concentrations of plasma bilirubin in observational and genetic analyses, suggesting that the association is causal.

IMPLICATIONS

Our results are compatible with two possible interpretations of previous observational studies, either that bilirubin is a mediator of smoking-induced respiratory disease or that the association between plasma bilirubin and respiratory disease stems from residual confounding because of smoking. Future studies should examine whether bilirubin is a causal risk factor for respiratory disease, or merely a marker of smoking status.

Prevalence, Characteristics, and Prognosis of Early Chronic Obstructive Pulmonary Disease. The Copenhagen General Population Study

Rationale: Identification of younger adults at high risk of developing chronic obstructive pulmonary disease (COPD) could lead to implementation of preventive measures before disease onset and halt progression.Objectives: To investigate the prevalence, characteristics, and prognosis of individuals with early COPD in the general population.Methods: We investigated 105,630 randomly chosen adults from a Danish contemporary population-based cohort. Early COPD was defined as FEV₁/FVC less than the lower limit of normal in individuals under 50 years of age with 10 pack-years or greater of tobacco consumption.Measurements and Main Results: Among 8,064 individuals under 50 years of age with 10 pack-years or greater of tobacco consumption, 1,175 (15%) had early COPD, of whom 58% were current smokers. Individuals with early COPD more often had chronic respiratory symptoms, severe lung function impairment, asthma, and a history with bronchitis/pneumonia. During the 14.4-year follow-up, we observed 117 acute hospitalizations with obstructive lung disease, 227 acute hospitalizations with pneumonia, and 185 deaths among the 8,064 younger adults. Compared with individuals without COPD, those with early COPD had multivariable adjusted hazard ratios of 6.42 (95% confidence interval, 3.39-12.2) for acute obstructive lung disease hospitalizations, 2.03 (1.43-2.88) for acute pneumonia hospitalizations, and 1.79 (1.28-2.52) for all-cause mortality.Conclusions: Among individuals under 50 years of age and 10 pack-years or greater of tobacco consumption from the general population, 15% fulfill criteria of early COPD. Individuals with early COPD more often have chronic respiratory symptoms and severe lung function impairment, and an increased risk of acute respiratory hospitalizations and early death.

Morbidity and mortality in carriers of the cystic fibrosis mutation CFTR Phe508del in the general population

Cystic fibrosis (CF) is caused by autosomal-recessive inheritance of a dysfunctional cystic fibrosis transmembrane conductance regulator (CFTR), up to 90% due to Phe508del mutation in the CFTR gene. We tested the hypothesis that CFTR Phe508del carriers have increased morbidity and mortality versus non-carriers in the general population.

We genotyped 108 035 randomly selected white Danish individuals from the Copenhagen General Population Study (aged from 20–100 years) for CFTR Phe508del mutation (rs113993960). Risk of chronic bronchitis and airflow limitation was assessed cross-sectionally. Overall survival and risk of bronchiectasis, lung cancer, pneumonia, chronic rhinosinusitis, airway bleeding, spontaneous pneumothorax, respiratory failure, acute and chronic pancreatitis, liver cirrhosis, ileus, gastric and colorectal cancer, and male infertility were assessed prospectively during up to 15 years of follow-up (median: 9 years). A single individual was excluded due to homozygosity for CFTR Phe508del and known CF. No other individuals had diagnosed CF at baseline examination or during follow-up.

Among the resulting 108 034 individuals, 105 176 (97%) were non-carriers and 2858 (3%) were carriers (i.e. were heterozygous for CFTR Phe508del). Overall survival was similar between carriers and non-carriers. Compared to non-carriers and with multivariable adjustment, carriers had an odds ratio (OR) of 1.31 (95% CI 1.16–1.48) for chronic bronchitis, a hazard ratio (HR) of 1.88 (95% CI 1.03–3.45) for bronchiectasis and 1.52 (95% CI 1.12–2.08) for lung cancer. Carriers did not differ from non-carriers concerning lung function or any other morbidity outcomes as mentioned above.

In the general population, carriers of CFTR Phe508del have a normal lifespan but an increased risk of chronic bronchitis (1.3-fold), bronchiectasis (1.9-fold) and lung cancer (1.5-fold).

Smoking, Systemic Inflammation, and Airflow Limitation: A Mendelian Randomization Analysis of 98 085 Individuals From the General Population

INTRODUCTION

Smoking is associated with systemic and local inflammation in the lungs. Furthermore, in chronic obstructive pulmonary disease, which is often caused by smoking, there is often systemic inflammation that is linked to lung function impairment. However, the causal pathways linking smoking, systemic inflammation, and airflow limitation are still unknown. We tested whether higher tobacco consumption is associated with higher systemic inflammation, observationally and genetically and whether genetically higher systemic inflammation is associated with airflow limitation.

METHODS

We included 98 085 individuals aged 20-100 years from the Copenhagen General Population Study; 36589 were former smokers and 16172 were current smokers. CHRNA3 rs1051730 genotype was used as a proxy for higher tobacco consumption and the IL6R rs2228145 genotype was used for higher systemic inflammation. Airflow limitation was defined as forced expiratory volume in 1 s (FEV1)/forced vital capacity (FVC) <70%.

RESULTS

Difference in plasma level of C-reactive protein was 4.8% (95% CI = 4.4% to 5.2%) per 10 pack-year increase and 1.6% (95% CI = 0.4% to 2.8%) per T allele. Corresponding differences were 1.2% (95% CI = 1.1% to 1.3%) and 0.5% (95% CI = 0.3% to 0.8%) for fibrinogen, 1.2% (95% CI = 1.2% to 1.3%) and 0.7% (95% CI = 0.5% to 1.0%) for α1-antitrypsin, 2.0% (95% CI = 1.8% to 2.1%) and 0.7% (95% CI = 0.4% to 1.1%) for leukocytes, 1.9% (95% CI = 1.8% to 2.1%) and 0.8% (95% CI = 0.4% to 1.2%) for neutrophils, and 0.8% (95% CI = 0.7% to 1.0%) and 0.4% (95% CI = 0.1% to 0.7%) for thrombocytes. The differences in these levels were lower for former smokers compared with current smokers. The IL6R rs2228145 genotype was associated with higher plasma acute-phase reactants but not with airflow limitation. Compared with the C/C genotype, the odds ratio for airflow limitation was 0.95 (95% CI = 0.89 to 1.02) for A/C genotype and 0.94 (95% CI = 0.87 to 1.01) for A/A genotype.

CONCLUSIONS

Higher tobacco consumption is associated with higher systemic inflammation both genetically and observationally, whereas systemic inflammation was not associated with airflow limitation genetically.

IMPLICATIONS

The association between higher tobacco consumption and higher systemic inflammation may be causal, and the association is stronger among current smokers compared to former smokers, indicating that smoking cessation may reduce the effects of smoking on systemic inflammation. Systemic inflammation does not seem to be a causal driver in development of airflow limitation. These findings can help to understand the pathogenic effects of smoking and the interplay between smoking, systemic inflammation, and airflow limitation and hence development and progression of chronic obstructive pulmonary disease.

25-Hydroxyvitamin D and Risk of Osteoporotic Fractures: Mendelian Randomization Analysis in 2 Large Population-Based Cohorts

Background

Whether low plasma 25-hydroxyvitamin D concentrations cause osteoporotic fractures is unclear. We tested the hypothesis that low plasma 25-hydroxyvitamin D concentrations are associated with increased risk of osteoporotic fractures using a Mendelian randomization analysis.

Methods

We genotyped 116 335 randomly chosen white Danish persons aged 20–100 years in 2 population-based cohort studies for plasma 25-hydroxyvitamin D decreasing genotypes in CYP2R1 (rs117913124 and rs12794714), DHCR7 (rs7944926 and rs11234027), GEMIN2 (rs2277458), and HAL (rs3819817); 35 833 had information on plasma 25-hydroxyvitamin D. We assessed risk of total, osteoporotic, and anatomically localized fractures from 1981 through 2017. Information on fractures and vital status was obtained from nationwide registries.

Results

During up to 36 years of follow-up, we observed 17 820 total fractures, 10 861 osteoporotic fractures, and 3472 fractures of hip or femur. Compared with individuals with 25-hydroxyvitamin D ≥ 50nmol/L, multivariable adjusted hazard ratios (95% CIs) for total fractures were 1.03 (0.97–1.09) for individuals with 25–49.9 nmol/L, 1.19 (1.10–1.28) for individuals with 12.5–24.9 nmol/L, and 1.39 (1.21–1.60) for individuals with 25-hydroxyvitamin D &lt; 12.5 nmol/L. Corresponding hazard ratios were 1.07 (1.00–1.15), 1.25 (1.13–1.37), and 1.49 (1.25–1.77) for osteoporotic fractures and 1.09 (0.98–1.22), 1.37 (1.18–1.57), and 1.41 (1.09–1.81) for fractures of hip or femur, respectively. Hazard ratios per 1 increase in vitamin D allele score, corresponding to 3.0% (approximately 1.6 nmol/L) lower 25-hydroxyvitamin D concentrations, were 0.99 (0.98–1.00) for total fractures, 0.99 (0.97–1.00) for osteoporotic fractures, and 0.98 (0.95–1.00) for fractures of hip or femur.

Conclusions

Low plasma 25-hydroxyvitamin D concentrations were associated with osteoporotic fractures; however, Mendelian randomization analysis provided no evidence supporting a causal role for vitamin D in the risk for osteoporotic fractures.

Loss-of-function polymorphism in IL6R reduces risk of JAK2V617F somatic mutation and myeloproliferative neoplasm: A Mendelian randomization study

BACKGROUND

Whether inflammation is independently associated with development of JAK2V617F mutation and myeloproliferative neoplasm is not clear. We tested the hypothesis that a loss-of-function polymorphism in IL6R (marked by rs4537545) reduces risk of JAK2V617F mutation and myeloproliferative neoplasm in a Mendelian randomization study.

METHODS

We genotyped 107,969 Danes from the Copenhagen General Population Study for the IL6R rs4537545 genotype, where the T-allele is associated with impaired interleukin-6 receptor signaling and reduced inflammation. JAK2V617F was examined in a subset of 49,143 individuals. We investigated the association between IL6R rs4537545 and risk of JAK2V617F using logistic regression and myeloproliferative neoplasm using Cox regression.

FINDINGS

36,871 were non-carriers, 52,500 heterozygotes, and 18,598 homozygotes for the T-allele of the IL6R rs4537545 genotype. Among 107,969 individuals, 352 were diagnosed with myeloproliferative neoplasm, and among 49,143 individuals, 62 were JAK2V617F-positive (of these 62 individuals, 46 had myeloproliferative neoplasm diagnosed). Compared to non-carriers, age- and sex-adjusted odds ratios for risk of JAK2V617F were 0·55(95%CI:0·32-0·94) in heterozygotes, 0·51(0·24-1·12) in homozygotes, 0·54(0·33-0·89) in carriers, and 0·66(0·45-0·96) per T-allele. Compared to non-carriers, age- and sex-adjusted hazard ratios for risk of myeloproliferative neoplasm were 0·82(95% CI: 0·65-1·02) in heterozygotes, 0·65(0·47-0·91) in homozygotes, 0·77(0·63-0·96) in carriers, and 0·81(0·70-0·94) per T-allele. Associations were primarily observed for polycythaemia vera and myelofibrosis, and for JAK2V617F-positive myeloproliferative neoplasm.

INTERPRETATION

A loss-of-function polymorphism in IL6R reduces risk of JAK2V617F mutation and myeloproliferative neoplasm. This finding supports inflammation as an independent risk factor for JAK2V617F mutation and myeloproliferative neoplasm and indicates that therapeutics designed to block interleukin-6 receptor signaling might prevent or retard progression of myeloproliferative neoplasm.

FUNDING

Karen Elise Jensen Foundation.

Two-fold risk of pneumonia and respiratory mortality in individuals with myeloproliferative neoplasm: A population-based cohort study

BACKGROUND

High cardiovascular comorbidity contributes to excess mortality in patients with myeloproliferative neoplasm, while less is known about respiratory comorbidity and mortality. We tested the hypothesis that individuals with myeloproliferative neoplasm have increased risk of pneumonia and respiratory mortality.

METHODS

Of 249 294 invited individuals aged ≥20 from the Danish general population from 2003-2015, 107 900 participated and were included in the Copenhagen General Population Study (response-rate: 43%). We examined lung function and respiratory symptoms at baseline examination and followed individuals prospectively from baseline examination through 2018 to determine risk of pneumonia and respiratory mortality using Cox proportional hazard regression. Among 351 individuals with myeloproliferative neoplasm, 131 (37%) were diagnosed at baseline examination and 220 (63%) were diagnosed during follow-up. The follow-up cases were entered in the regression analysis by using a time-varying variable.

FINDINGS

In total, 125 (36%) individuals had essential thrombocythaemia, 124 (35%) had polycythaemia vera, and 102 (29%) had myelofibrosis/unclassifiable myeloproliferative neoplasm. During follow-up we observed 5979 pneumonias and 2278 respiratory deaths. Compared to individuals without myeloproliferative neoplasm, multivariable adjusted hazard ratios in individuals with myeloproliferative neoplasm were 2·18 (95% CI: 1·60-2·96) for pneumonia and 2·27 (1·46-3·53) for respiratory mortality. Corresponding hazard ratios were 1·26 (0·71-2·30) and 0·96 (0·31-2·94) for essential thrombocythaemia, 2·50 (1·57-3·98) and 3·58 (1·94-6·59) for polycythaemia vera, and 3·03 (1·86-4·93) and 2·40 (1·11-5·19) for myelofibrosis/unclassifiable myeloproliferative neoplasm, respectively. Results were similar in those with and without airflow limitation, and in never-smokers and ever-smokers separately.

INTERPRETATION

Individuals with myeloproliferative neoplasm had two-fold increased risk of pneumonia and respiratory mortality, mainly due to polycythaemia vera and myelofibrosis/unclassifiable myeloproliferative neoplasm. These are novel findings.

Chronic Cough in Individuals With COPD: A Population-Based Cohort Study

BACKGROUND

The role and impact of chronic cough in individuals with COPD have not been described in the general population. This study hypothesized that comorbid chronic cough is a marker of disease severity in individuals with COPD.

METHODS

This study identified individuals with COPD and chronic cough, and recorded respiratory symptoms, health-care utilizations, lung function, and inflammatory biomarkers in blood in a nested cohort of 43,271 adults from the Copenhagen General Population Study (CGPS).

RESULTS

Among 43,271 individuals from the general population, 8,181 (19%) experienced COPD, of whom 796 (10%) had chronic cough. Individuals with COPD and chronic cough had a Leicester Cough Questionnaire median (25th-75th percentiles) total score of 17.7 (16.0-18.9), corresponding to 5.9 (5.3-6.3) for the physical domain, 5.6 (4.9-6.3) for the psychological domain, and 6.3 (5.8-6.8) for the social domain. Among individuals with COPD, those with chronic cough vs those without chronic cough more often experienced sputum production (60% vs 8%), wheezing (46% vs 14%), dyspnea (66% vs 38%), chest pain/tightness (9% vs 4%), nighttime dyspnea (8% vs 3%), episodes of acute bronchitis/pneumonias in the last 10 years (45% vs 25%), and ≥ 3 general practitioner visits in the past 12 months (53% vs 37%). Furthermore, these individuals had lower FEV₁ % predicted (81% vs 89%) and FEV₁/FVC (0.64 vs 0.66), as well as higher levels of high-sensitivity C-reactive protein, fibrinogen, leukocytes, neutrophils, eosinophils, and IgE in blood.

CONCLUSIONS

Comorbid chronic cough in individuals with COPD is associated with a more severe disease in terms of more respiratory symptoms and health-care utilizations, lower lung function, and increased inflammation in blood.