Lifetime lung function is related to quality of life and longevity. Over the lifespan, individual... more Lifetime lung function is related to quality of life and longevity. Over the lifespan, individuals follow different lung function trajectories. Identification of these trajectories, their determinants, and outcomes is important, but no study has done this beyond the fourth decade. We used six waves of the Tasmanian Longitudinal Health Study (TAHS) to model lung function trajectories measured at 7, 13, 18, 45, 50, and 53 years. We analysed pre-bronchodilator FEV z-scores at the six timepoints using group-based trajectory modelling to identify distinct subgroups of individuals whose measurements followed a similar pattern over time. We related the trajectories identified to childhood factors and risk of chronic obstructive pulmonary disease (COPD) using logistic regression, and estimated population-attributable fractions of COPD. Of the 8583 participants in the original cohort, 2438 had at least two waves of lung function data at age 7 years and 53 years and comprised the study popula...
International journal of chronic obstructive pulmonary disease, 2017
We have explored whether assessing the degree of concavity in the descending limb of the maximum ... more We have explored whether assessing the degree of concavity in the descending limb of the maximum expiratory flow-volume curve enhanced spirometric detection of early small airway disease. We used spirometry records from 890 individuals aged ≥40 years (mean 59 years), recruited for the Burden of Obstructive Lung Disease Australia study. Central and peripheral concavity indices were developed from forced expired flows at 50% and 75% of the forced vital capacity, respectively, using an ideal line joining peak flow to zero flow. From the 268 subjects classified as normal never smokers, mean values for post-bronchodilator central concavity were 18.6% in males and 9.1% in females and those for peripheral concavity were 50.5% in males and 52.4% in females. There were moderately strong correlations between concavity and forced expired ratio (forced expiratory volume in 1 second/forced vital capacity) and mid-flow rate (forced expiratory flow between 25% and 75% of the FVC [FEF25%-75%]; r=-0...
Current evidence concerning the impact of exposure to traffic-related air pollution (TRAP) on adu... more Current evidence concerning the impact of exposure to traffic-related air pollution (TRAP) on adult respiratory morbidity mainly comes from cross-sectional studies. We sought to establish more robust measures of this association and potential gene-environment interactions using longitudinal data from an established cohort study.Associations between measures of TRAP (nitrogen dioxide (NO2) and distance to major roads) and wheeze, asthma prevalence and lung function were investigated in participants of the Tasmanian Longitudinal Health Study at 45- and 50-year follow-ups. Generalised estimating equations were used to quantify associations and the potential modifying effect of glutathione S-transferase gene variants.Living <200 m from a major road was associated with increased prevalence of current asthma and wheeze, and lower lung function. The association between living <200 m from a major road and current asthma and wheeze was more marked for carriers of the GSTT1 null and GST...
International journal of molecular sciences, Jan 8, 2017
Systemic inflammation is an integral part of chronic obstructive pulmonary disease (COPD), and ai... more Systemic inflammation is an integral part of chronic obstructive pulmonary disease (COPD), and air pollution is associated with cardiorespiratory mortality, yet the interrelationships are not fully defined. We examined associations between nitrogen dioxide (NO₂) exposure (as a marker of traffic-related air pollution) and pro-inflammatory cytokines, and investigated effect modification and mediation by post-bronchodilator airflow obstruction (post-BD-AO) and cardiovascular risk. Data from middle-aged participants in the Tasmanian Longitudinal Health Study (TAHS, n = 1389) were analyzed by multivariable logistic regression, using serum interleukin (IL)-6, IL-8 and tumor necrosis factor-α (TNF-α) as the outcome. Mean annual NO₂ exposure was estimated at residential addresses using a validated satellite-based land-use regression model. Post-BD-AO was defined by post-BD forced expiratory ratio (FEV₁/FVC) < lower limit of normal, and cardiovascular risk by a history of either cerebrova...
International journal of chronic obstructive pulmonary disease, 2016
Personal smoking is widely regarded to be the primary cause of chronic bronchitis (CB) in adults,... more Personal smoking is widely regarded to be the primary cause of chronic bronchitis (CB) in adults, but with limited knowledge of contributions by other factors, including current asthma. We aimed to estimate the independent and relative contributions to adult CB from other potential influences spanning childhood to middle age. The population-based Tasmanian Longitudinal Health Study cohort, people born in 1961, completed respiratory questionnaires and spirometry in 1968 (n=8,583). Thirty-seven years later, in 2004, two-thirds responded to a detailed postal survey (n=5,729), from which the presence of CB was established in middle age. A subsample (n=1,389) underwent postbronchodilator spirometry between 2006 and 2008 for the assessment of chronic airflow limitation, from which nonobstructive and obstructive CB were defined. Multivariable and multinomial logistic regression models were used to estimate relevant associations. The prevalence of CB in middle age was 6.1% (95% confidence i...
Existing evidence that supports maternal smoking to be a potential risk factor for chronic obstru... more Existing evidence that supports maternal smoking to be a potential risk factor for chronic obstructive pulmonary disease (COPD) for adult offspring has barely been mentioned in major guideline documents, suggesting a need for more robust and consistent data. We aimed to examine whether such early life exposure can predispose to COPD in middle age, possibly through its interaction with personal smoking. The fifth-decade follow-up of the Tasmanian Longitudinal Health Study cohort, which was first studied in 1968 (n = 8583), included a 2004 postal survey (n = 5729 responses) and subsequent laboratory attendance (n = 1389) for comprehensive lung function testing between 2006 and 2008. Multivariable linear and logistic regression models included sampling weights. Post-bronchodilator airflow obstruction (less than fifth percentile) was detected for 9.3% (n = 123) of middle-aged offspring. Its association with heavy maternal smoking (>20 cigarettes/day) during childhood was 2.7-fold hig...
Epidemiological data on asthma suggest a sex difference that varies with age. Hormonal effects ha... more Epidemiological data on asthma suggest a sex difference that varies with age. Hormonal effects have been suggested as a possible explanation for these differences but there is a scarcity of evidence on these relationships. Our objective was to examine the relationship between reproductive factors and asthma risk among females and to examine whether body mass index (BMI) modifies this relationship.Female participants in the 2004 fifth decade follow-up postal survey of the Tasmanian Longitudinal Health Study formed the study population. Reproductive history and data on hormonal contraceptive (HC) use were collected on 2764 females. Multiple logistic regression was used to assess the association between the reproductive factors and current asthma.The mean age of participants was 43 years and the prevalence of middle-aged current asthma was 12.8%. Females with very early menarche (≤10 years) had higher odds of middle-aged current asthma (OR 1.91, 95% CI 1.14–3.2). Pregnancy history (num...
Differences between early-onset and late-onset adult asthma have not been comprehensively describ... more Differences between early-onset and late-onset adult asthma have not been comprehensively described using prospective data. To characterise the differences between early-onset and late-onset asthma in a longitudinal cohort study. The Tasmanian Longitudinal Health Study (TAHS) is a population-based cohort. Respiratory histories and spirometry were first performed in 1968 when participants were aged 7 (n=8583). The cohort was traced and resurveyed from 2002 to 2005 (n=5729 responses) and a sample, enriched for asthma and bronchitis participated in a clinical study when aged 44 (n=1389). Of the entire TAHS cohort, 7.7% (95% CI 6.6% to 9.0%) had early-onset and 7.8% (95% CI 6.4% to 9.4%) late-onset asthma. Atopy and family history were more common in early-onset asthma while female gender, current smoking and low socioeconomic status were more common in late-onset asthma. The impact on lung function of early-onset asthma was significantly greater than for late-onset asthma (mean difference prebronchodilator (BD) FEV1/FVC -2.8% predicted (-5.3 to -0.3); post-BD FEV1FVC -2.6% predicted (-5.0 to -0.1)). However, asthma severity and asthma score did not significantly differ between groups. An interaction between asthma and smoking was identified and found to be associated with greater fixed airflow obstruction in adults with late-onset asthma. This interaction was not evident in adults with early-onset disease. Early-onset and late-onset adult asthma are equally prevalent in the middle-aged population. Major phenotypic differences occur with asthma age-of-onset; while both share similar clinical manifestations, the impact on adult lung function of early-onset asthma is greater than for late-onset asthma.
Few studies have examined common childhood infections and adult asthma. We examined associations ... more Few studies have examined common childhood infections and adult asthma. We examined associations between childhood infectious diseases, childhood pneumonia, and current, persisting, and incident asthma to middle age. We analyzed data from the Tasmanian Longitudinal Health Study (TAHS). A history of pneumonia was ascertained from their parents when the TAHS participants were 7 years old. Measles, rubella, mumps, chickenpox, diphtheria, and pertussis were identified from school medical records. Associations with current, persisting, or incident asthma were examined using regression techniques. Greater infectious diseases load was negatively associated with persisting asthma at all ages. Individually, pertussis (adjusted OR [aOR], 0.53; 95% CI, 0.28-1.00) was negatively associated with asthma persisting to age 13 years, chickenpox (aOR, 0.58; 95% CI, 0.38-0.88) was negatively associated with asthma persisting to age 32 years, and rubella was negatively associated with asthma persisting to ages 32 (aOR, 0.61; 95% CI, 0.31-0.96) and 44 years (aOR 0.53; 95% CI, 0.35-0.82). Pertussis was associated with preadolescent incident asthma (adjusted hazard ratio [aHR], 1.80; 95% CI, 1.10-2.96), whereas measles was associated with adolescent incident asthma (aHR, 1.66; 1.06-2.56). Childhood pneumonia was associated with current asthma at ages 7 (aOR, 3.12; 95% CI, 2.61-3.75) and 13 years (aOR, 1.32; 95% CI, 1.00-1.75), an association stronger in those without than those with eczema (aOR, 3.46; 95% CI, 2.83-4.24 vs aOR, 2.08; 95% CI, 1.38-3.12). Overall, childhood infectious diseases protected against asthma persisting in later life, but pertussis and measles were associated with new-onset asthma after childhood. Measles and pertussis immunization might lead to a reduction in incident asthma in later life.
The aim of this analysis was to examine associations between lung health in childhood and mortali... more The aim of this analysis was to examine associations between lung health in childhood and mortality between ages 18 and 44 years in the Tasmanian Longitudinal Health Study (TAHS). The 1961 Tasmanian birth cohort who attended school in 1968 (n=8583) were linked to the Australian National Death Index (NDI) to identify deaths. Additional deaths were notified by families through a 37 year follow-up postal questionnaire. Information on lung health at age 7 years and on potential confounders was obtained from the original 1968 TAHS survey and school medical records. Cox proportional hazards modelling was used to assess determinants of mortality. A total of 264 (3%) deaths were identified. The principal causes of death were external injury (56.1%, n=97) and cancer (17.9%, n=31). Males were more likely than females to have died (p=<0.1). Only two (1.1%) participants had died from respiratory conditions. Having an FEV(1)<80% predicted at 7 years of age was associated with a 2-fold incr...
Tracheal obstruction (TO) stimulates growth of hypoplastic lungs in the fetus, but there is littl... more Tracheal obstruction (TO) stimulates growth of hypoplastic lungs in the fetus, but there is little knowledge of subsequent postnatal respiratory function. We have determined the effectiveness of TO in fetal sheep with existing lung hypoplasia in restoring postnatal respiratory function. Lung hypoplasia was induced by lung liquid drainage from 112 days of gestation to term ( approximately 148 days). We used an untreated group (ULH), a treated group (TLH) in which the trachea was obstructed for 10 days, and a control group. ULH lambs died within 4 h of birth. TLH lambs were hypoxic for the first week and were hypercapic at 2 days. Pulmonary diffusing capacity, gas volumes, and respiratory compliances were not different between control and TLH lambs. Minute ventilation was not different between the two groups; however, tidal volumes were lower and respiratory frequencies were higher in TLH lambs than in controls for 2 wk after birth. We conclude that 10 days of TO in the presence of initial lung hypoplasia prevents death at birth and returns most aspects of pulmonary function to normal by 1-2 wk after birth.
Lifetime lung function is related to quality of life and longevity. Over the lifespan, individual... more Lifetime lung function is related to quality of life and longevity. Over the lifespan, individuals follow different lung function trajectories. Identification of these trajectories, their determinants, and outcomes is important, but no study has done this beyond the fourth decade. We used six waves of the Tasmanian Longitudinal Health Study (TAHS) to model lung function trajectories measured at 7, 13, 18, 45, 50, and 53 years. We analysed pre-bronchodilator FEV z-scores at the six timepoints using group-based trajectory modelling to identify distinct subgroups of individuals whose measurements followed a similar pattern over time. We related the trajectories identified to childhood factors and risk of chronic obstructive pulmonary disease (COPD) using logistic regression, and estimated population-attributable fractions of COPD. Of the 8583 participants in the original cohort, 2438 had at least two waves of lung function data at age 7 years and 53 years and comprised the study popula...
International journal of chronic obstructive pulmonary disease, 2017
We have explored whether assessing the degree of concavity in the descending limb of the maximum ... more We have explored whether assessing the degree of concavity in the descending limb of the maximum expiratory flow-volume curve enhanced spirometric detection of early small airway disease. We used spirometry records from 890 individuals aged ≥40 years (mean 59 years), recruited for the Burden of Obstructive Lung Disease Australia study. Central and peripheral concavity indices were developed from forced expired flows at 50% and 75% of the forced vital capacity, respectively, using an ideal line joining peak flow to zero flow. From the 268 subjects classified as normal never smokers, mean values for post-bronchodilator central concavity were 18.6% in males and 9.1% in females and those for peripheral concavity were 50.5% in males and 52.4% in females. There were moderately strong correlations between concavity and forced expired ratio (forced expiratory volume in 1 second/forced vital capacity) and mid-flow rate (forced expiratory flow between 25% and 75% of the FVC [FEF25%-75%]; r=-0...
Current evidence concerning the impact of exposure to traffic-related air pollution (TRAP) on adu... more Current evidence concerning the impact of exposure to traffic-related air pollution (TRAP) on adult respiratory morbidity mainly comes from cross-sectional studies. We sought to establish more robust measures of this association and potential gene-environment interactions using longitudinal data from an established cohort study.Associations between measures of TRAP (nitrogen dioxide (NO2) and distance to major roads) and wheeze, asthma prevalence and lung function were investigated in participants of the Tasmanian Longitudinal Health Study at 45- and 50-year follow-ups. Generalised estimating equations were used to quantify associations and the potential modifying effect of glutathione S-transferase gene variants.Living <200 m from a major road was associated with increased prevalence of current asthma and wheeze, and lower lung function. The association between living <200 m from a major road and current asthma and wheeze was more marked for carriers of the GSTT1 null and GST...
International journal of molecular sciences, Jan 8, 2017
Systemic inflammation is an integral part of chronic obstructive pulmonary disease (COPD), and ai... more Systemic inflammation is an integral part of chronic obstructive pulmonary disease (COPD), and air pollution is associated with cardiorespiratory mortality, yet the interrelationships are not fully defined. We examined associations between nitrogen dioxide (NO₂) exposure (as a marker of traffic-related air pollution) and pro-inflammatory cytokines, and investigated effect modification and mediation by post-bronchodilator airflow obstruction (post-BD-AO) and cardiovascular risk. Data from middle-aged participants in the Tasmanian Longitudinal Health Study (TAHS, n = 1389) were analyzed by multivariable logistic regression, using serum interleukin (IL)-6, IL-8 and tumor necrosis factor-α (TNF-α) as the outcome. Mean annual NO₂ exposure was estimated at residential addresses using a validated satellite-based land-use regression model. Post-BD-AO was defined by post-BD forced expiratory ratio (FEV₁/FVC) < lower limit of normal, and cardiovascular risk by a history of either cerebrova...
International journal of chronic obstructive pulmonary disease, 2016
Personal smoking is widely regarded to be the primary cause of chronic bronchitis (CB) in adults,... more Personal smoking is widely regarded to be the primary cause of chronic bronchitis (CB) in adults, but with limited knowledge of contributions by other factors, including current asthma. We aimed to estimate the independent and relative contributions to adult CB from other potential influences spanning childhood to middle age. The population-based Tasmanian Longitudinal Health Study cohort, people born in 1961, completed respiratory questionnaires and spirometry in 1968 (n=8,583). Thirty-seven years later, in 2004, two-thirds responded to a detailed postal survey (n=5,729), from which the presence of CB was established in middle age. A subsample (n=1,389) underwent postbronchodilator spirometry between 2006 and 2008 for the assessment of chronic airflow limitation, from which nonobstructive and obstructive CB were defined. Multivariable and multinomial logistic regression models were used to estimate relevant associations. The prevalence of CB in middle age was 6.1% (95% confidence i...
Existing evidence that supports maternal smoking to be a potential risk factor for chronic obstru... more Existing evidence that supports maternal smoking to be a potential risk factor for chronic obstructive pulmonary disease (COPD) for adult offspring has barely been mentioned in major guideline documents, suggesting a need for more robust and consistent data. We aimed to examine whether such early life exposure can predispose to COPD in middle age, possibly through its interaction with personal smoking. The fifth-decade follow-up of the Tasmanian Longitudinal Health Study cohort, which was first studied in 1968 (n = 8583), included a 2004 postal survey (n = 5729 responses) and subsequent laboratory attendance (n = 1389) for comprehensive lung function testing between 2006 and 2008. Multivariable linear and logistic regression models included sampling weights. Post-bronchodilator airflow obstruction (less than fifth percentile) was detected for 9.3% (n = 123) of middle-aged offspring. Its association with heavy maternal smoking (>20 cigarettes/day) during childhood was 2.7-fold hig...
Epidemiological data on asthma suggest a sex difference that varies with age. Hormonal effects ha... more Epidemiological data on asthma suggest a sex difference that varies with age. Hormonal effects have been suggested as a possible explanation for these differences but there is a scarcity of evidence on these relationships. Our objective was to examine the relationship between reproductive factors and asthma risk among females and to examine whether body mass index (BMI) modifies this relationship.Female participants in the 2004 fifth decade follow-up postal survey of the Tasmanian Longitudinal Health Study formed the study population. Reproductive history and data on hormonal contraceptive (HC) use were collected on 2764 females. Multiple logistic regression was used to assess the association between the reproductive factors and current asthma.The mean age of participants was 43 years and the prevalence of middle-aged current asthma was 12.8%. Females with very early menarche (≤10 years) had higher odds of middle-aged current asthma (OR 1.91, 95% CI 1.14–3.2). Pregnancy history (num...
Differences between early-onset and late-onset adult asthma have not been comprehensively describ... more Differences between early-onset and late-onset adult asthma have not been comprehensively described using prospective data. To characterise the differences between early-onset and late-onset asthma in a longitudinal cohort study. The Tasmanian Longitudinal Health Study (TAHS) is a population-based cohort. Respiratory histories and spirometry were first performed in 1968 when participants were aged 7 (n=8583). The cohort was traced and resurveyed from 2002 to 2005 (n=5729 responses) and a sample, enriched for asthma and bronchitis participated in a clinical study when aged 44 (n=1389). Of the entire TAHS cohort, 7.7% (95% CI 6.6% to 9.0%) had early-onset and 7.8% (95% CI 6.4% to 9.4%) late-onset asthma. Atopy and family history were more common in early-onset asthma while female gender, current smoking and low socioeconomic status were more common in late-onset asthma. The impact on lung function of early-onset asthma was significantly greater than for late-onset asthma (mean difference prebronchodilator (BD) FEV1/FVC -2.8% predicted (-5.3 to -0.3); post-BD FEV1FVC -2.6% predicted (-5.0 to -0.1)). However, asthma severity and asthma score did not significantly differ between groups. An interaction between asthma and smoking was identified and found to be associated with greater fixed airflow obstruction in adults with late-onset asthma. This interaction was not evident in adults with early-onset disease. Early-onset and late-onset adult asthma are equally prevalent in the middle-aged population. Major phenotypic differences occur with asthma age-of-onset; while both share similar clinical manifestations, the impact on adult lung function of early-onset asthma is greater than for late-onset asthma.
Few studies have examined common childhood infections and adult asthma. We examined associations ... more Few studies have examined common childhood infections and adult asthma. We examined associations between childhood infectious diseases, childhood pneumonia, and current, persisting, and incident asthma to middle age. We analyzed data from the Tasmanian Longitudinal Health Study (TAHS). A history of pneumonia was ascertained from their parents when the TAHS participants were 7 years old. Measles, rubella, mumps, chickenpox, diphtheria, and pertussis were identified from school medical records. Associations with current, persisting, or incident asthma were examined using regression techniques. Greater infectious diseases load was negatively associated with persisting asthma at all ages. Individually, pertussis (adjusted OR [aOR], 0.53; 95% CI, 0.28-1.00) was negatively associated with asthma persisting to age 13 years, chickenpox (aOR, 0.58; 95% CI, 0.38-0.88) was negatively associated with asthma persisting to age 32 years, and rubella was negatively associated with asthma persisting to ages 32 (aOR, 0.61; 95% CI, 0.31-0.96) and 44 years (aOR 0.53; 95% CI, 0.35-0.82). Pertussis was associated with preadolescent incident asthma (adjusted hazard ratio [aHR], 1.80; 95% CI, 1.10-2.96), whereas measles was associated with adolescent incident asthma (aHR, 1.66; 1.06-2.56). Childhood pneumonia was associated with current asthma at ages 7 (aOR, 3.12; 95% CI, 2.61-3.75) and 13 years (aOR, 1.32; 95% CI, 1.00-1.75), an association stronger in those without than those with eczema (aOR, 3.46; 95% CI, 2.83-4.24 vs aOR, 2.08; 95% CI, 1.38-3.12). Overall, childhood infectious diseases protected against asthma persisting in later life, but pertussis and measles were associated with new-onset asthma after childhood. Measles and pertussis immunization might lead to a reduction in incident asthma in later life.
The aim of this analysis was to examine associations between lung health in childhood and mortali... more The aim of this analysis was to examine associations between lung health in childhood and mortality between ages 18 and 44 years in the Tasmanian Longitudinal Health Study (TAHS). The 1961 Tasmanian birth cohort who attended school in 1968 (n=8583) were linked to the Australian National Death Index (NDI) to identify deaths. Additional deaths were notified by families through a 37 year follow-up postal questionnaire. Information on lung health at age 7 years and on potential confounders was obtained from the original 1968 TAHS survey and school medical records. Cox proportional hazards modelling was used to assess determinants of mortality. A total of 264 (3%) deaths were identified. The principal causes of death were external injury (56.1%, n=97) and cancer (17.9%, n=31). Males were more likely than females to have died (p=<0.1). Only two (1.1%) participants had died from respiratory conditions. Having an FEV(1)<80% predicted at 7 years of age was associated with a 2-fold incr...
Tracheal obstruction (TO) stimulates growth of hypoplastic lungs in the fetus, but there is littl... more Tracheal obstruction (TO) stimulates growth of hypoplastic lungs in the fetus, but there is little knowledge of subsequent postnatal respiratory function. We have determined the effectiveness of TO in fetal sheep with existing lung hypoplasia in restoring postnatal respiratory function. Lung hypoplasia was induced by lung liquid drainage from 112 days of gestation to term ( approximately 148 days). We used an untreated group (ULH), a treated group (TLH) in which the trachea was obstructed for 10 days, and a control group. ULH lambs died within 4 h of birth. TLH lambs were hypoxic for the first week and were hypercapic at 2 days. Pulmonary diffusing capacity, gas volumes, and respiratory compliances were not different between control and TLH lambs. Minute ventilation was not different between the two groups; however, tidal volumes were lower and respiratory frequencies were higher in TLH lambs than in controls for 2 wk after birth. We conclude that 10 days of TO in the presence of initial lung hypoplasia prevents death at birth and returns most aspects of pulmonary function to normal by 1-2 wk after birth.
Uploads
Papers by David Johns