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Background The extent to which airflow obstruction, a key feature of COPD, can be already present in early adulthood is unclear. We investigated the prevalence of airflow obstruction in young adults across European populations.

Methods We identified 48 612 individuals aged 20–40 years across eight population-based European cohorts in the Chronic Airway Diseases Early Stratification (CADSET) collaboration and applied two commonly used definitions of airflow obstruction: pre-bronchodilator forced expiratory volume in 1 s (FEV1)/forced vital capacity (FVC) <0.70 and below the lower limit of normal (LLN). We explored how the prevalence of airflow obstruction according to both criteria was related to age, sex and smoking.

Results Airflow obstruction prevalence increased with increasing age from 2.3% in those aged 20–24.9 years to 6.3% in those aged 35–39.9 years according to FEV1/FVC <0.70, and from 7.3% to 8.3% according to FEV1/FVC <LLN. The corresponding increase in airflow obstruction prevalence was up to 8.8% in males versus 7.5% in females, and up to 9.0% in ever-smokers versus 6.9% in never-smokers. Difference in prevalence of airflow obstruction between FEV1/FVC <0.70 and <LLN was highest for females and ever-smokers. Active smoking ranged from 19% to 28% and ever-smoking from 37% to 51%. The prevalence of airflow obstruction increased with pack-years, plateauing at ∼5 pack-years.

Conclusion Up to 8% of young adults across Europe have airflow obstruction; its cause and its role in prior, concurrent and future airway disease merit further investigation.

Background: Respiratory symptoms are common in the general adult population. Increased burden of respiratory symptoms may increase the risk of mortality. We assessed the association between respiratory symptom clusters and mortality.

Methods: Participants were derived from two population-based Swedish adult cohorts (N = 63,060). Cluster analysis was performed with Locality Sensitive Hashing (LSH)-k-prototypes in subjects with ≥ 1 self-reported respiratory symptom. Linked mortality register data (up to 21 years of follow-up, > 600,000 person-years) were used. Associations between clusters and all-cause/cause-specific mortality were assessed using asymptomatic subjects as reference.

Results: Over 60% reported ≥ 1 respiratory symptom and ~ 30% reported ≥ 5 respiratory symptoms. Five clusters were identified, partly overlapping with established respiratory disease phenotypes but many individuals were undiagnosed: (1) "low-symptomatic" (30.3%); (2) "allergic nasal symptoms" (10.7%); (3) "allergic nasal symptoms, wheezing, and dyspnea attacks" (4.7%); (4) "wheezing and dyspnea attacks" (6.6%); (5) "recurrent productive cough and wheezing" (4.1%). All but Cluster 2 were associated with all-cause mortality, highest risk for Cluster 3 (hazard ratio 1.4, 95% confidence interval 1.13–1.73) and Cluster 5 (1.4, 1.22–1.61). Comparable associations were seen for cardiovascular mortality. For respiratory mortality, Cluster 4 (2.02, 1.18–3.46) and Cluster 5 (1.89, 1.1–3.25) were most strongly associated.

Conclusions: Respiratory symptoms are common in the general adult population, with identifiable clusters. These clusters have clinical relevancy as they are differentially associated with mortality and relatively weakly correlated with diagnosed respiratory disease.

Background: Longitudinal studies on allergic rhinitis (AR) incidence and remission from childhood to adulthood are limited. This study aimed to estimate AR incidence and remission from age 8 to 19 years and to identify related risk factors.

Methods: In 2006, all children in grades 1 and 2 (median age 8 years) in three municipalities in Northern Sweden were invited to participate in a questionnaire survey. The children in two of the municipalities underwent a skin prick test (SPT) for airborne allergens. The protocol was repeated at age 19 years. In total, 2250 participants (91% participation rate) completed the questionnaire, and 1338 underwent SPTs at 8 and 19 years of age.

Results: From age 8 to 19 years, the cumulative incidence of AR was 33.6%, significantly higher among girls than boys (37.4% vs. 29.8%, p <.001). Factors that independently increased the risk of developing AR were sensitisation by age 8 (adjusted odds ratio [aOR] 3.75, 95% confidence interval [CI] 2.68–5.23), sensitisation between 8 and 19 years (aOR 2.57, 95% CI 1.82–3.63), and female sex (aOR 1.71, 95% CI 1.30–2.26). The remission rate was 40.0%, with boys experiencing significantly higher remission than girls (45.4% vs. 32.2%, p =.015). The probability of remission was decreased by sensitisation before (aOR 0.26, 95% CI 0.13–0.53) and after age 8 years (aOR 0.20, 95% CI 0.05–0.77).

Conclusion: This study found a high incidence of AR between age 8 and 19 years, especially among girls, while boys had a higher remission rate. Sensitisation increased the risk of developing AR and decreased the remission rate.

Introduction: Computational sciences have significantly contributed to characterizing airway disease phenotypes, complementing medical expertise. However, comparing studies that derive phenotypes is challenging due to varying decisions made during phenotyping. We conducted a systematic review to describe studies that utilized unsupervised computational approaches for phenotyping obstructive airway diseases in children and adults.

Methods: We searched for relevant papers published between 2010 and 2020 in PubMed, EMBASE, Scopus, Web of Science, and Google Scholar. Additional sources included conference proceedings, reference lists, and expert recommendations. Two reviewers independently screened studies for eligibility, extracted data, and assessed study quality. Disagreements were resolved by a third reviewer. An in-house quality appraisal tool was used. Evidence was synthesized, focusing on populations, variables, and computational approaches used for deriving phenotypes.

Results: Of 120 studies included in the review, 60 focused on asthma, 19 on severe asthma, 28 on COPD, 4 on asthma-COPD overlap (ACO), and 9 on rhinitis. Among asthma studies, 31 focused on adults and 9 on children, with phenotypes related to atopy, age at onset, and disease severity. Severe asthma phenotypes were characterized by symptomatology, atopy, and age at onset. COPD phenotypes involved lung function, emphysematous changes, smoking, comorbidities, and daily life impairment. ACO and rhinitis phenotypes were mostly defined by symptoms, lung function, and sensitization, respectively. Most studies used hierarchical clustering, with some employing latent class modeling, mixture models, and factor analysis. The comprehensiveness of variable reporting was the best quality indicator, while reproducibility measures were often lacking.

Conclusion: Variations in phenotyping methods, study settings, participant profiles, and variables contribute to significant differences in characterizing asthma, severe asthma, COPD, ACO, and rhinitis phenotypes across studies. Lack of reproducibility measures limits the evaluation of computational phenotyping in airway diseases, underscoring the need for consistent approaches to defining outcomes and selecting variables to ensure reliable phenotyping.

Background: Aeroallergen sensitization is a major factor in asthma, and asthma is associated with impaired lung function. The independent association between sensitization and lung function is unclear.

Objectives: To examine factors associated with lung function in adolescence, with special interests in sensitization and asthma.

Methods: All schoolchildren in grade one and two (median age 8) in two municipalities in Northern Sweden were invited to a questionnaire survey of allergic diseases and skin prick tests to aeroallergens. This was repeated at ages 12 and, at 19 years also including spirometry and n = 1495 participated at all three occasions. Associations between risk factors and FEV1, FVC and FEV1/FVC were analysed by linear regression.

Results: Aeroallergen sensitization was not associated with lung function, irrespective of age at onset, type or degree of sensitization. Early-onset asthma, both persistent (B −0.35, 95% CI –0.60 to −0.09) and in remission (B −0.43, 95% CI –0.74 to −0.12) was associated with lower FEV1. Persistent asthma was associated with lower FEV1/FVC (B −0.81, 95% CI –1.07 to −0.55), and remission with lower FVC (B −0.37, 95% CI –0.67 to −0.70). No interaction between asthma and sensitization was found. Maternal smoking in pregnancy was associated with lower FEV1/FVC. Underweight at age 19 years was associated with lower FEV1 and FVC and overweight was associated with higher FEV1 and FVC, but lower FEV1/FVC.

Conclusions: Aeroallergen sensitization was not independently associated with lung function. Early onset asthma was strongly associated with lung function impairments in young adulthood and in sensitized and non-sensitized individuals alike.

Background: Exposure to high levels of vehicle traffic during childhood seems to have a negative effect on lung function. Less is known about the effects of exposure to relatively low levels during childhood. We aimed to study how exposure to vehicle traffic in childhood is associated with lung function and asthma in young adulthood in a 10-year follow-up of a population-based cohort in a municipality with relatively low levels of vehicle traffic.

Methods: The Obstructive Lung Disease in Northern Sweden (OLIN) pediatric cohort II was recruited in 2006 at age 8 years. Exposure to vehicle traffic at baseline was studied in relation to lung function at follow-up at age 19 years (n = 1056 participants). Lung function measures included FEV1, FVC and FEV1/FVC. Different exposure thresholds were defined based on proximity (within a 200 m radius from the home address) to a road with a minimum daily count of heavy vehicles (≥ 250 and ≥ 500) or any type of vehicle (≥ 4000 and ≥ 8000). The association between exposure to vehicle traffic at baseline and lung function at follow-up was analyzed by linear regression adjusting for potential confounders.

Results: In general, those above the exposure thresholds had lower lung function than those below, but not significantly so in all comparisons. Those exposed to ≥ 250 heavy vehicles/day had lower mean FEV1 z-score at follow-up (-0.38) compared with those exposed to < 250 heavy vehicles/day (-0.21), p = 0.033, and this association remained after adjustment for confounders (p = 0.036). Also, those exposed to ≥ 8000 vehicles/day had lower mean FVC z-score (-0.19) than those exposed to < 8000 vehicles/day (-0.02), p = 0.047, with p = 0.032 after adjustment.

Conclusions: Exposure to vehicle traffic in childhood, in a relatively low traffic-flow environment, may be associated with a slightly lower lung function in young adulthood.

Background: COPD is largely underdiagnosed. Active identification of cases is crucial to establish preventive measures before manifestation of clinical disease. The significance of different spirometric patterns preceding COPD, especially preserved ratio impaired spirometry (PRISm), has been highlighted but remains unclear.

Research Question: Which clinical characteristics, smoking habits, and spirometric patterns, with primary focus on PRISm findings, precede the development of airway obstruction (AO)?

Study Design and Methods: The OLIN COPD Study was established from 2002 through 2004. After re-examination of population-based cohorts, individuals with AO (n = 993; FEV1 to VC ratio < 0.70) were identified together with control participants without AO (n = 993; FEV1 to VC ratio ≥ 0.70). Most of these people had participated in examinations during the 1980s or 1990s, and in total, 902 cases and 819 control participants had previous clinical data. Logistic regression was performed with case status as outcome and spirometric patterns, age, sex, smoking habits, and BMI at first examination as covariates.

Results: The mean (SD) person-years between first examination and inclusion in the OLIN COPD Study was 10.5 (4.0) years. At first examination, the prevalence of PRISm was higher in cases (18.6%) vs control participants (13.4%). Current smoking was more common in cases (45.1% vs 18.2%), whereas former smoking was similar (31.8% vs 34.9%). Cases reported more respiratory symptoms (78.0% vs 44.3%) than control participants. At first examination, PRISm, current smoking, and former smoking were strongly associated with becoming a case when adjusted for confounders, with adjusted OR (aOR) of 3.5, 4.1, and 1.5, respectively. When stratifying for smoking habits, aORs for PRISm in those with current smoking, former smoking, and nonsmoking status were 2.9, 3.8 and 3.7, respectively.

Interpretation: In this study, PRISm was associated with transition into AO corresponding to COPD within 1 decade, independent of smoking habits and with similar strength of association among those who have never smoked, who formerly smoked, and who currently smoke.

Nickel allergy is common among children. The present study investigated prevalence trends of self-reported nickel allergy, risk factors, and atopic comorbidity among children. Eight-year-old children from Norrbotten County, Sweden, were recruited in 1996 (n = 3,430), 2006 (n = 2,585), and 2017 (n = 2,785). Self-reported nickel allergy decreased from 7.7% (2006) to 6.1% (2017; p = 0.024) and was significantly more common among girls. In 1996, only children with atopic dermatitis answered questions on nickel allergy. Among children with atopic dermatitis, no significant decrease was seen over the years 1996 to 2017. Ear piercing (odds ratio [OR] 1.93, 95% confidence interval [CI] 1.39-2.68 and OR 5.57, 95% CI 3.71-8.38) and female sex (OR 4.05, 95% CI 2.68-6.13 and OR 1.73, 95% CI 1.09-2.74) were risk factors for self-reported nickel allergy in 2006 and 2017, respectively. Self-reported nickel allergy was significantly more prevalent among children with atopic dermatitis than without in 2006 (12.3% vs 6.4%; p < 0.001) and 2017 (11.5% vs 5.1%; p < 0.001), and among children with allergic rhinitis in 2017 (8.6% vs 4.7%; p = 0.015). In conclusion, we found a decreasing prevalence of self-reported nickel allergy, but not among children with atopic dermatitis. Ear piercing and female sex were strongly associated with nickel allergy. Our findings also suggest that nickel allergy is associated with atopic dermatitis and allergic rhinitis.

Background: Chronic airway obstruction (CAO) and restrictive spirometry pattern (RSP) are associated with mortality, but sex-specific patterns of all-cause and specific causes of death have hardly been evaluated.

Objectives: To study the possible sex-dependent differences of all-cause mortality and patterns of cause-specific mortality among men and women with CAO and RSP, respectively, to that of normal lung function (NLF).

Design: Population-based prospective cohort study.

Methods: Individuals with CAO [FEV1/vital capacity (VC) < 0.70], RSP [FEV₁/VC ⩾ 0.70 and forced vital capacity (FVC) < 80% predicted] and NLF (FEV₁/VC ⩾ 0.70 and FVC ⩾ 80% predicted) were identified within the Obstructive Lung Disease in Northern Sweden (OLIN) studies in 2002–2004. Mortality data were collected through April 2016, totally covering 19,000 patient-years. Cox regression and Fine–Gray regression accounting for competing risks were utilized to estimate hazard ratios (HRs) with 95% confidence intervals (CIs) adjusted for age, body mass index, sex, smoking habits and pack-years.

Results: The adjusted hazard for all-cause mortality was higher in CAO and RSP than in NLF (HR, 95% CI; 1.69, 1.31–2.02 and 1.24, 1.06–1.71), and the higher hazards were driven by males. CAO had a higher hazard of respiratory and cardiovascular death than NLF (2.68, 1.05–6.82 and 1.40, 1.04–1.90). The hazard of respiratory death was significant in women (3.41, 1.05–11.07) while the hazard of cardiovascular death was significant in men (1.49, 1.01–2.22). In RSP, the higher hazard for respiratory death remained after adjustment (2.68, 1.05–6.82) but not for cardiovascular death (1.11, 0.74–1.66), with a similar pattern in both sexes.

Conclusion: The higher hazard for all-cause mortality in CAO and RSP than in NLF was male driven. CAO was associated with respiratory death in women and cardiovascular death in men, while RSP is associated with respiratory death, similarly in both sexes.