Ergonomic and individual risk factors for musculoskeletal pain in the ageing workforce.

BACKGROUND: The present study aimed to investigate the possible association between specific ergonomic and individual risk factors and musculoskeletal pain (MSP) in the back, shoulder, hip and knee region in workers aged 50-65y. METHODS: The study was a population based cross-sectional survey. The study population comprised citizens born between 1952-1966, living in Esbjerg municipality, Denmark, ultimo 2016 (n = 23,463). A questionnaire was sent electronically or by mail. The analysis included the working population only. A multivariate logistic regression was used for each of the following dependent variables; musculoskeletal pain for the past 3 months in the back, shoulder, hip and knee, where independent variables included ergonomic exposure, age, sex, body mass index (BMI) and leisure time physical activity (LTPA). RESULTS: The overall response rate was 58% and the data of individuals at work (n = 9,263) demonstrated several ergonomic exposures with increased odds for pain in specific regions. Exposure to back twisted or bend, squatting or lying on knees and to carrying or lifting were associated with musculoskeletal pain in the back, whereas exposure to back twisted or bend, arms above shoulder and repeated arm movement were associated with pain in the shoulder. Exposure to back twisted or bend, repeated arm movement, squatting or lying on knees and to carrying or lifting were associated with musculoskeletal pain in the hip. Important individual risk factors were also identified. Increasing age was significantly associated with increased pain in the hip but associated with less risk for pain in the back and shoulder. Males had higher odds for pain in the back and knee compared to females but lower odds for pain in the hip. BMI was particularly important for knee pain. The level of LTPA did not have an important association with MSP in any region. CONCLUSION: There is a significant positive association between ergonomic exposures and musculoskeletal pain, which were specific for the back, shoulder, hip and knee. In addition, the data demonstrated a differential association with age, sex and BMI. This needs to be considered for the treatment and classification of musculoskeletal pain and for future preventive initiatives.

Pyromellitic dianhydride (PMDA) may cause occupational asthma.

INTRODUCTION: Anhydrides are widely used as cross-linking agents in epoxy resins and alkyd production, for example, as coatings and adhesives in plastic products. Sensitisation to several anhydrides is known to cause occupational asthma. There are indications that the lesser known pyromellitic dianhydride (PMDA) can cause irritative respiratory symptoms and possibly asthma. We report three cases of workers from a plastic foil manufacturing plant, who developed asthma when exposed to PMDA during specific inhalation challenge (SIC). METHODS: SIC was performed over 2 days according to recommendations of European Respiratory Society. Lactose powder was used in control challenges and a mixture of 10% PMDA and 90% lactose powder in active challenges. RESULTS: All cases experienced a delayed decrease in forced expiratory flow in 1 s (FEV1) 4-12 hours after active challenge. FEV1 decreased by 19%, 15% and 16%, respectively. After 21 hours, FEV1 decreased by 24% in one worker. DISCUSSION: Respiratory symptoms after working hours may represent delayed work-related asthma. During SIC, the three patients developed lower respiratory symptoms and a delayed decrease in FEV1 which suggest sensitisation. The mechanism of anhydride-related asthma is not well understood. Anhydrides are known irritants and hence an irritative response cannot be excluded. The company improved ventilation and enforced the use of respiratory protection equipment, and finally phased out PMDA. Occupational workplace risk identification may help to identify exposures. SIC can contribute to improving working conditions, by identifying and confirming asthmogens in the environment.

Are allergen batch differences and the use of double skin prick test important?

BACKGROUND: Skin prick tests (SPT) are widely used both in clinical diagnostics and in research. The standardization of allergen extracts is well documented to be crucial for the validity of SPT, whereas less emphasis has been placed on reproducibility and the SPT procedure itself. The objectives of this study are to clarify how the double skin prick test procedure influence the sensitivity and specificity of the test and to analyse the differences in weal size in skin prick tests between two batches of allergen extracts from the same vendor. METHODS: The association between rhinitis and SPT was assessed among 1135 persons from a general population sample. SPT was performed twice with 10 common aeroallergens. In a subsample of 90 persons SPT was performed simultaneously with five of the allergens using different batches. RESULTS: Thirty percent had at least one positive SPT. Among asthmatics this number was 62%. Only minor differences were seen between the sizes of two weals from the same batch. A second SPT with the same batch did not change the association between rhinitis and sensitization. When performing SPT with two different batches disagreement was observed in 2% (Birch) to 11% (Cat) of the subjects. CONCLUSIONS: Performing SPT twice with the same allergen batch does not enhance the validity of the test, and value of double testing can be questioned. Considerable differences in SPT response with different batches from the same manufacturer were observed. Thus inter batch differences in allergen extracts might be a source of variability.

Prevalence of Obesity-Related Disease in a Danish Population - The Results of an Algorithm-Based Screening Program.

Purpose: The prevalence of obesity continues to rise. People with obesity are at increased risk of several diseases. We tested an algorithm-based screening program for people with a BMI above 30 kg/m2 and present data on the prevalence of previously undiagnosed obesity-related diseases. Patients and Methods: Seven hundred and sixty-nine persons with BMI > 30 kg/m2 and age 18-60 years were screened for diabetes (assessed by glycosylated hemoglobin and oral glucose tolerance test at HbA1c 43-48 mmol/mol), sleep apnea (screened by questionnaires and assessed by cardiorespiratory monitoring at indication of sleep disorder), liver steatosis or liver fibrosis (assessed by biochemistry and fibroscan) and arterial hypertension (assessed by both office and 24-hour blood pressure measurement). A reference group of people with a BMI of 18.5-29.9 kg/m2 was established. Results: Of those referred, 73.0% were women. We identified new diabetes in 4.2%, prediabetes in 9.1%, moderate-to-severe sleep apnea in 25.1%, increased liver fat and increased liver stiffness in 68.1% and 17.4%, respectively, and hypertension or masked hypertension in 19.0%. The prevalence of diseases was much higher among men and increased with BMI. Except for hypertension, we found few participants with undiagnosed disease in the reference group. Conclusion: An algorithm-based screening program is feasible and reveals undiagnosed obesity-related disease in a large proportion of the participants. The disproportional referral pattern calls for a tailored approach aiming to include more men with obesity. Trial Registration: Inclusion of the non-obese group was approved by the Scientific Ethics Committee of The Region of Southern Denmark (project identification number: S-20210091), and the study was reported at clinicaltrials.gov (NCT05176132).

The number of people with obesity is going up, and they are at a higher risk for various diseases. We tested a screening program for people referred with a BMI over 30 kg/m² and presented the prevalence of diseases related to obesity. We screened 769 people aged 18 to 60 years with a BMI over 30 kg/m² for diabetes (biochemistry and glucose tolerance test), sleep apnea (both questionnaires and home monitoring), liver disease (biochemistry and liver scan) and high blood pressure (office and 24-hour readings). We also tested a reference group of people with BMI 18.5-30 kg/m². Among those screened, 73.0% were women. We found new cases of diabetes in 4.2%, prediabetes in 9.1%, sleep apnea in 25.1%, increased liver fat in 68.1%, increased liver stiffness in 17.4%, and hypertension or masked hypertension in 19.0%. The diseases were more common in men and increased with both higher BMI and age. Except for hypertension, we found few cases in the reference groups. The screening program uncovered undiagnosed obesity-related diseases in a large group of individuals. The uneven distribution of referrals suggests we need a customized approach to include more men with obesity.

Consequences of asthma on job absenteeism and job retention.

AIMS: Various social and economic effects are associated with asthma. This quantitative study describes the effects of current asthma on work life evaluated from the number of weeks receiving transfer incomes. METHODS: The study population comprised 7,241 persons answering the ECRHS II screening questionnaire, which was sent to a random age and gender stratified sample of 10,000 persons aged 20 to 44 years. Participants with current asthma were identified by positive answers to a set of validated questions. Transfer incomes for a five-year period were registered from a study-independent national database, which collects all public administered transfer incomes in Denmark. The numbers of weeks receiving unemployment, welfare, sick-leave and disability benefits were identified for each participant and differences between asthmatics and non-asthmatics were analyzed. RESULTS: Asthmatics had significantly more annual weeks receiving welfare (36.6 vs. 20.7, p=0.00), sick leave (9.2 vs. 6.6, p=0.00) and disability (19.3 vs. 11.4, p=0.00) benefits than non-asthmatics. Adult-onset asthmatics had increased prevalence rate ratios for disability of 2.40 (95% confidence interval 1.70-3.40). Blue collar work significantly increased the probability of all public transfer incomes. CONCLUSIONS: Current asthma makes it harder to keep a job. Adult-onset asthmatics and blue collar workers are particularly affected.

Workability in the Ageing Workforce-A Population-Based Cross-Sectional Study.

BACKGROUND: The purpose of this study was to investigate the impact of age, musculoskeletal pain and ergonomic exposure on workability in the oldest group of workers. METHODS: The study was a population based cross-sectional survey. The study population comprised citizens born between 1952-1966, living in Esbjerg municipality ultimo 2016 (n = 23,463). A questionnaire was sent electronically or by mail. The analysis included the working population only. A stereotype logistic regression was used with the primary dependent variable being workability and independent variables included age, musculoskeletal pain, and ergonomic exposure. RESULTS: The response rate was 58% and the data demonstrated a significant negative association between age and workability. With excellent workability as a reference, the odds for poor workability increased by 97% being 60+ y compared to 50-55 y. Both moderate intensity and severe musculoskeletal pain in the back, shoulder and knee/hip all showed significantly higher odds for poor workability. Ergonomic exposures, such as standing/walking, working with back bent or twisted and carrying or lifting had a significant negative impact on workability. CONCLUSION: Age, musculoskeletal pain and ergonomic exposures showed a significant negative impact on workability in the oldest group of workers and should be targeted with preventive initiatives.

Sex determines the influence of smoking and gene polymorphism on glutathione peroxidase activity in erythrocytes.

OBJECTIVE: Glutathione peroxidase 1 (GPX1) is one of the major oxidative enzymes. Our aim was to characterize factors influencing its activity and to determine whether or not the activity is associated with asthma. MATERIAL AND METHODS: Serum selenium concentration was measured, GPX1 polymorphisms were genotyped and smoking history was obtained in a Danish population-derived case-base cohort of 1,191 subjects designed to evaluate risk factors for asthma. GPX1 activity was measured in 134 male and 164 female subjects equally distributed according to genotype of GPX1. Among these subjects, 82 (28 %) had doctor-diagnosed asthma. RESULTS: The average serum selenium concentration was too low for optimal enzyme activity (mean (SE), 83.4 (0.76) ng/mL). GPX1 activity in men was lower than in women, 52.6 (0.66) and 56.4 (0.59) U/g protein, respectively (p<0.001). In men, activity was positively associated with serum selenium concentration (p = 0.005) and negatively associated with both active smoking (p = 0.009) and exposure to environmental tobacco smoke (p = 0.02). In women, activity was associated with genotypes with 59.2 (1.4), 56.0 (1.4) and 54.2 (1.4) U/g protein in the homozygote wild-type, the heterozygote and the homozygote variant type, respectively (p = 0.001). Doctor-diagnosed asthma was unrelated to GPX1 activity in either sex. CONCLUSION: Determinants for activity in the oxidative enzyme GPX1 show marked differences between the sexes, but the activity is not associated with asthma. Sex ought to be taken into consideration when analysing the activity of the enzyme.

Intake of paracetamol and risk of asthma in adults.

Intake of paracetamol has been associated with development of asthma. The aim of this study was to address a possible association between intake of paracetamol and risk of adult-onset asthma. Using a multidisciplinary postal questionnaire survey concerning health and lifestyle we prospectively studied 19,349 adult twins enrolled in the nationwide Danish Twin Registry. There was a higher prevalence of new-onset asthma in subjects who reported frequent intake of paracetamol at baseline compared with subjects without this determinant (12.0% vs. 4.3%), OR = 3.03 (1.51-6.11), p = 0.005. The result remained significant after adjusting for sex, age, smoking, BMI, hay fever, eczema, and intake of medications other than paracetamol, OR = 2.16 (1.03-4.53), p = 0.041. Frequent intake of paracetamol is an independent risk factor for adult-onset asthma.

Risk factors for incident asthma and COPD in a cohort of young adults.

INTRODUCTION: The aim of the study was to describe potential shared risk factors for incident asthma and COPD in a population-based, 9-year follow-up study. METHODS: From a cohort of 1191 individuals, aged 20-44, who participated in baseline survey including spirometry, bronchial challenge, and skin prick test (SPT) 742 subjects (62%) were reexamined at follow-up in 2012-2014. RESULTS: A total of 27 incident cases of asthma and 22 cases of COPD were identified at follow-up corresponding to an incidence rate of 5.8 (95% CI 3.9-8.4) and 3.5 (2.2-5.3) per 1000 person years, respectively. Among the identified COPD cases a total of 12 were Asthma-COPD Overlap Syndrome (ACOS). Atopy defined by positive SPT was a risk factor for asthma in males (OR 7.54; 95% CI 1.24-45.90), whereas risk factors in females were nasal allergy (3.81; 1.20-12.11), FEV1 <100% predicted (3.96; 1.07-14.62) and parental asthma (3.06; 1.00-9.40). Risk factors for COPD in males were bronchial hyperresponsiveness (23.13; 1.41-380.50) and FEV1 <100% predicted (all male cases had FEV1 <100% predicted) and in females current smoking (3.34; 1.16-9.59) and asthma at baseline (5.21; 1.48-18.34). CONCLUSIONS: No shared risk factors for incident asthma and COPD were found. Despite low power when stratifying by sex risk factors for incident asthma and COPD emphasize considerable gender differences.

Determinants of persistent asthma in young adults.

Objective: The aim of the study was to evaluate determinants for the prognosis of asthma in a population-based cohort of young adults. Design: The study was a nine-year clinical follow up of 239 asthmatic subjects from an enriched population-based sample of 1,191 young adults, aged 20-44 years, who participated in an interviewer-administered questionnaire and clinical examination at baseline in 2003-2006. From the interview, an asthma score was generated as the simple sum of affirmative answers to five main asthma-like symptoms in order to analyse symptoms of asthma as a continuum. The clinical examination comprised spirometry, bronchial challenge or bronchodilation, and skin prick test. Results: Among the 239 individuals with asthma at baseline 164 (69%) had persistent asthma at follow up, while 68 (28%) achieved remission of asthma and seven (3%) were diagnosed with COPD solely. Determinants for persistent asthma were use of medication for breathing within the last 12 months: Short-acting beta-adrenoceptor agonists (SABA) only (OR 3.39; 95%CI: 1.47-7.82) and inhaled corticosteroids (ICS) and/or long-acting beta-adrenoceptor agonists (LABA) (8.95; 3.87-20.69). Stratified by age of onset determinants for persistence in individuals with early-onset asthma (age less than 16 years) were FEV1 below predicted (7.12; 1.61-31.50), asthma score at baseline (2.06; 1.15-3.68) and use of ICS and/or LABA within 12 months (9.87; 1.95-49.98). In individuals with late-onset asthma the determinant was use of ICS and/or LABA within 12 months (6.84; 2.09-22.37). Conclusions: Pulmonary function below predicted, severity of disease expressed by asthma score and use of ICS and/or LABA were all determinants for persistent early-onset asthma, whereas only use of ICS and/or LABA was a determinant in late-onset asthma. A high asthma score indicated insufficient disease control in a substantial proportion of these young adults.

Genetic and environmental contributions to hay fever among young adult twins.

BACKGROUND: The susceptibility to develop hay fever is putatively the result both of genetic and environmental causes. We estimated the significance and magnitude of genetic and environmental contributions to hay fever among young adult twins. METHODS: From the birth cohorts 1953-82 of The Danish Twin Registry 11,750 twin pairs were identified through a nationwide questionnaire survey. Subjects were regarded hay fever cases when responding affirmatively to the question 'Do you have, or have you ever had hay fever?' Latent factor models of genetic and environmental effects were fitted to the observed data using maximum likelihood methods. RESULTS: The overall cumulative prevalence of hay fever was 12.6%. Identical twins were significantly more likely to be concordant for hay fever than were fraternal twins (P<0.001). Additive genetic effects accounted for 71% and non-shared environmental effects accounted for 29% of the individual susceptibility to hay fever. The same genes contributed to the susceptibility to hay fever both in males and in females. In families with asthma, the susceptibility to develop hay fever was, in addition to genes, to a great extent ascribable to family environment, whereas the aetiology of 'sporadic' hay fever was mainly genetic. CONCLUSIONS: The susceptibility to develop hay fever is attributable to major genetic influences. However, effects of family environment and upbringing are also of importance in families where asthma is present. These results indicate that different sub-forms of hay fever may have different aetiologies.

The incidence of asthma in young adults.

STUDY OBJECTIVES: Longitudinal data on adult asthma are sparse. The objectives of this study were to determine the incidence of asthma and to establish the risk factors for the development of asthma in subjects who were 12 to 41 years old over an 8-year period. DESIGN: From birth cohorts over the period 1953 to 1982 in The Danish Twin Registry, 19,349 subjects with no history of asthma, as determined by a questionnaire-based survey in 1994, answered a follow-up questionnaire in 2002. The subjects were regarded as incident asthma cases when answering "yes" to the question "Do you have, or have you ever had asthma?" in 2002, and "no" to the same question in 1994. RESULTS: A total of 838 cases (4.3%) of new asthma were identified in 2002. The incidence rates of asthma were 4.5 and 6.4 per 1,000 person-years, respectively, among male and female subjects. For all ages, the probability of adult-onset asthma was greater for female subjects (odds ratio [OR], 1.49; p < 0.001), and for both sexes there was a slow decline in probability with increasing age. There was a positive association between increasing body mass index (BMI) and risk of adult-onset asthma applying to both sexes (OR, 1.05 per unit; p < 0.001). Furthermore, positive associations were found between incident asthma and a history of hay fever (OR: male subjects, 4.2; female subjects, 3.7; p < 0.001), eczema (OR: male subjects, 3.5; female subjects, 2.0; p < 0.001), and both (OR: male subjects, 6.9; female subjects, 8.0; p < 0.001). CONCLUSIONS: There is a continuing high incidence of asthma past childhood that is most pronounced among female subjects. Increasing levels of BMI are associated with a greater likelihood of developing asthma for both sexes. A substantial portion of cases of adult asthma is preceded by upper airway allergic symptoms and/or eczema, thus indicating a shared pathogenesis.

Occupational exposure during pregnancy and the risk of hay fever in 7-year-old children.

OBJECTIVES: The prevalence of allergic diseases including hay fever has increased in the last decades, especially in Westernised countries. The aim of this study was to analyse whether occupational exposure during pregnancy is associated with development of hay fever in 7-year-old Danish children. METHODS: A total of 42,696 women and their children from the Danish National Birth Cohort were categorised according to maternal occupational exposure. Exposure information was obtained by combining job title in pregnancy with a commonly used asthma Job Exposure Matrix. Information on hay fever in the child was obtained by an internet questionnaire at follow-up at 7 years of age. RESULTS: Adjusted logistic regression analyses showed no significant association between maternal occupational exposure during pregnancy and hay fever among the 7-year-old children. Stratifying for atopic status in the children did not change the results. The prevalence of hay fever was 10.0% in the atopic children compared with 3.6% in the non-atopic children. Maternal atopic disposition increased the risk of hay fever in the offspring, odds ratio (OR) 2.49 [95% confidence interval (CI) 2.26; 2.74]. Rural residence during pregnancy decreased the risk for hay fever [OR 0.74 (95% CI 0.59; 0.92)] as did parity, OR 0.72 (95% CI 0.66; 0.80) and 0.70 (95% CI 0.48; 1.00) for 2nd and 3rd child, respectively, compared with the firstborn child. CONCLUSION: The results suggest that occupational exposure among pregnant women in Denmark is not a risk factor for hay fever among young children.

Maternal occupational exposure to asthmogens during pregnancy and risk of asthma in 7-year-old children: a cohort study.

OBJECTIVES: The objective of this study was to examine whether maternal exposure to asthmogens during pregnancy is associated with the development of asthma in 7-year-old Danish children, taking atopic status and sex into consideration. DESIGN: The study is a prospective follow-up of a birth cohort. SETTING AND PARTICIPANTS: A total of 41 724 women and their children from The Danish National Birth Cohort were categorised according to maternal occupational exposure. Exposure information was obtained by combining job title in pregnancy and 18 months after pregnancy with a commonly used asthma Job Exposure Matrix. PRIMARY AND SECONDARY OUTCOME MEASURES: Primary outcome was parent-reported asthma among their 7-year-old children in an internet-based questionnaire. Secondary outcome was asthma among the same children with or without atopic dermatitis and among boys and girls, respectively. RESULTS: Prenatal exposure to low molecular weight (LMW) agents was borderline associated with asthma in children with OR 1.17 (0.95 to 1.44) for children with atopic dermatitis and 1.10 (0.98 to 1.22) for children without. Maternal postnatal exposure was associated with asthma (OR 1.15 (1.04 to 1.28). After mutual adjustment,postnatal exposure (OR 1.13 (0.99 to 1.29) and the combined effects of prenatal and postnatal exposure (OR 1.34 (1.19 to 1.51)) seem to increase the risk of asthma in children. No significant associations were observed for other prenatal or postnatal exposures. The gender of the child did not modify the aforementioned associations. CONCLUSIONS: Maternal occupational exposures during pregnancy do not seem to be a substantial risk factor for the development of asthma in 7-year-old children. Maternal prenatal and postnatal exposures to LMW agents may predispose the propensity of the children to develop asthma. Future studies should prioritise the characterisation of the timing of exposure in relation to the birth.

Intake of alcohol and risk of adult-onset asthma.

AIM: To examine the association between intake of alcohol and risk of adult-onset asthma. METHODS: Using data from two multidisciplinary questionnaire surveys we prospectively studied 19,349 twins, 12-41 years of age, from the nationwide Danish Twin Registry. RESULTS: The eight-year incidence of asthma was 4.3%. After adjustment for sex, age, BMI, physical activity, educational level and smoking, the risk of new-onset asthma was significantly related to overall alcohol intake in a U-shaped manner with the lowest risk observed in the group with a moderate weekly intake of alcohol (1-6 units/week), p = 0.006. The highest risk of asthma was observed in rare/never drinkers (<1 unit/month), OR = 1.59 (1.25-2.02), p = 0.000, whereas the risk of asthma in heavy daily drinkers (≥4 units/day) was also increased, however not statistically significant, OR = 1.13 (0.54-2.36), p = 0.747. The risk of new-onset asthma was lower for subjects with wine preference (3.3%) compared with beer preference (4.3%) or no preference (4.4%). After multivariable adjustment, wine preference was inversely related to incident asthma compared with beer preference. However, this finding was not statistically significant, OR = 0.87 (0.51-1.46), p = 0.590. CONCLUSION: Alcohol intake is associated with new-onset asthma in adults with a U-shaped association between amount of alcohol intake and the risk of asthma.

Genetic polymorphisms in antioxidative enzymes are associated to forced expiratory volume in 1 s (FEV1) in smokers independently of asthma.

INTRODUCTION: In this study, we hypothesised that the genotypes coding for low antioxidative enzyme activity are associated with asthma and reduced lung function. METHODS: Using the European Community Respiratory Health Survey protocol, we enlisted 1091 Danish subjects in this cross-sectional study. Asthma phenotypes were defined as asthma symptoms in combination with steroid usage, bronchial hyperresponsiveness and atopy. These phenotypes and lung function were analysed with respect to glutathione peroxidase, GPX1 (Pro198Leu, rs1050450), manganese superoxide dismutase, SOD2 (Ala16Val, rs4880) and three glutathione S-transferases; GSTP1 (Ile105Val, rs1695), GSTT1 (gene copy number) and GSTM1 (gene copy number). RESULTS: We found no associations between these genotypes and the asthma phenotypes. For the 201 subjects identified as current smokers and recruited via random sampling, an association was seen between increasing number of genotypes coding for high antioxidative enzyme activity (GPX1 Pro/Pro, SOD2 Val/Val, GSTP1 Ile/Ile, GSTT1 two copies, GSTM1 two copies) and forced expiratory volume in 1 s (FEV1%) predicted. The increase in FEV1% predicted was 2.0% (95% confidence interval 0.3-3.8) per genotype. There was no identified significance for the inverse association between FEV1% predicted and number of genotypes coding for low antioxidative enzyme activity. CONCLUSION: The present study does not support the hypothesis that asthma is associated with genotypes of these major antioxidative enzymes. However, we speculate that since we see an impact of these genotypes on lung function in young adult smokers, polymorphisms in antioxidative enzymes may contribute to the range of susceptibility of smokers have to Chronic obstructive lung disease.

Increase in the heritability of asthma from 1994 to 2003 among adolescent twins.

BACKGROUND: Over the past decades the prevalence of asthma has increased in most parts of the world, and widespread changes in lifestyle and environment have been postulated as the primary cause for this. We examined whether the extent to which genetic and environmental factors influence susceptibility to asthma has changed between 1994 and 2003. METHODS: Two different cohorts of twins (n = 3393 and n = 2813 pairs), both 12-20 years of age, from the Danish Twin Registry, participated in questionnaire studies nine years apart. Prevalence of asthma and resemblance between twins for asthma was compared between the two cohorts. RESULTS: The prevalence of asthma increased from 7.1% in 1994 to 10.8% in 2003, p < 0.001. The change was significant both in males (7.7 vs. 12.4%, p < 0.001); and females (6.6 vs. 9.2%, p < 0.001). The best-fitting model, which included additive genetic and non-shared environmental effects, showed that the heritability of asthma increased significantly from 79% in 1994 to 91% in 2003, p = 0.005. CONCLUSIONS: This result could indicate that environmental changes over the past years have increased the expression of genes and thus have lead to a higher heritability in the succeeding cohort. This is consistent with the hypothesis that changes in the environment, particular in childhood, are the cause of the increase in the prevalence of asthma over the past decades.

Differences in associations between markers of antioxidative defense and asthma are sex specific.

BACKGROUND: Lungs are exposed to high levels of oxygen, air pollutants, and smoke, all of which stimulate the production of reactive oxygen species (ROS). In addition, inflammatory cells produce ROS, and thus there may be increased demand for antioxidants, including antioxidant enzymes, in inflammatory lung diseases such as asthma. Sex-specific differences have been noted for asthma, which in postpubertal subjects is predominantly found in females. These sex-specific differences may be associated with differences on the molecular level as well. OBJECTIVE: The aim of this cross-sectional study was to examine associations between markers of antioxidative defense and asthma, and to investigate whether these associations were different between women and men. METHODS: Based on the European Community Respiratory Health Survey protocol, subjects were enrolled in a study of asthma risk factors. The multicenter study was conducted in 5 west Danish counties between 2003 and 2006, and the subjects were recruited as a case-enriched random sample of 10,000 Danish inhabitants aged 20 to 44 years selected by their civil registration number. Participants were identified by positive answers to asthma questions on a screening questionnaire, random sampling, or both. Serum selenium concentrations and antioxidant enzyme activities (superoxide dismutase, glutathione peroxidase [GPX], glutathione reductase [GR], and glucose-6-phosphate dehydrogenase [G6PD]) in erythrocytes were measured. Asthma was defined as either current asthma symptoms with bronchial hyperresponsiveness (BHR) or a continuous asthma score based on 8 questions. RESULTS: A total of 1191 mostly white women and men (mean [SD] age, 34.0 [7.1] and 35.1 [7.1] years, respectively) were enrolled in the study. Current asthma symptoms were present in 29.9% (200/670) of women and 22.5% (117/521) of men, with women reporting more positive answers (51.1% vs 40.9%, respectively; P < 0.01) to asthma questions. Serum selenium concentrations were measured in 1151 subjects (640 women, 511 men), and antioxidant enzyme activities were measured in 295 subjects (161 women, 134 men). Women had higher enzyme activities of most antioxidant enzymes (GPX, P = 0.006; GR, P < 0.001; and G6PD, P = 0.009) than did men. Although the serum selenium concentration was inversely associated with asthma in both sexes, there was a female preponderance, with 3.5% lower serum selenium in subjects with current asthma symptoms with BHR (n = 77) compared with controls (n = 287). GR activity was associated with asthma in men, with 5.7% higher enzyme activity in subjects with current asthma symptoms with BHR (n = 14) compared with controls (n = 77). However, a significant interaction with gender was observed for analyses of GR (P = 0.02), but not for analyses of selenium. CONCLUSIONS: In this study of asthma risk factors, women had higher levels of enzyme activities than did men in a randomly selected Danish population, and sex-specific differences were found in the associations between markers of antioxidative defense and asthma.