BACKGROUND:Concentrations of outdoor nitrogen dioxide (NO2) have been associated with increased mortality. Hazard ratios (HRs) from cohort studies are used to assess population health impact and ...burden. We undertook meta-analyses to derive concentration–response functions suitable for such evaluations and assessed their sensitivity to study selection based upon cohort characteristics.
METHODS:We searched online databases and existing reviews for cohort studies published to October 2016 reporting HRs for NO2 and mortality. We calculated meta-analytic summary estimates using fixed/random effects models.
RESULTS:We identified 48 articles analyzing 28 cohorts. Meta-analysis of HRs found positive associations between NO2 and all-cause (1.02 (95% CI1.01, 1.03); prediction interval (PI)(0.99, 1.06) per 10µg/m increment in NO2), cardiovascular (1.03 (95% CI1.02,1.05); PI(0.98, 1.08)) , respiratory (1.03 (95% CI1.01,1.05); PI(0.97, 1.10)) and lung cancer mortality (1.05 (95% CI1.02,1.08); PI(0.94, 1.17)) with evidence of substantial heterogeneity between studies. In subgroup analysis, summary HRs varied by age at cohort entry, spatial resolution of pollution estimates, and adjustment for smoking and body mass index at the individual level; for some sub-groups the HR was close to unity, with lower confidence limits below 1.
CONCLUSIONS:Given the many uncertainties inherent in the assessment of this evidence base and the sensitivity of health impact calculations to small changes in the magnitude of the HRs, calculation of the impact on health of policies to reduce long-term exposure to NO2 should use prediction intervals and report ranges of impact rather than focusing upon point estimates.This is an open-access article distributed under the terms of the Creative Commons Attribution-Non Commercial-No Derivatives License 4.0 (CCBY-NC-ND), where it is permissible to download and share the work provided it is properly cited. The work cannot be changed in any way or used commercially without permission from the journal.
ObjectivesWhile there is good evidence for associations between short-term exposure to ozone and a range of adverse health outcomes, the evidence from narrative reviews for long-term exposure is ...suggestive of associations with respiratory mortality only. We conducted a systematic, quantitative evaluation of the evidence from cohort studies, reporting associations between long-term exposure to ozone and mortality.MethodsCohort studies published in peer-reviewed journals indexed in EMBASE and MEDLINE to September 2015 and PubMed to October 2015 and cited in reviews/key publications were identified via search strings using terms relating to study design, pollutant and health outcome. Study details and estimate information were extracted and used to calculate standardised effect estimates expressed as HRs per 10 ppb increment in long-term ozone concentrations.Results14 publications from 8 cohorts presented results for ozone and all-cause and cause-specific mortality. We found no evidence of associations between long-term annual O3 concentrations and the risk of death from all causes, cardiovascular or respiratory diseases, or lung cancer. 4 cohorts assessed ozone concentrations measured during the warm season. Summary HRs for cardiovascular and respiratory causes of death derived from 3 cohorts were 1.01 (95% CI 1.00 to 1.02) and 1.03 (95% CI 1.01 to 1.05) per 10 ppb, respectively.ConclusionsOur quantitative review revealed a paucity of independent studies regarding the associations between long-term exposure to ozone and mortality. The potential impact of climate change and increasing anthropogenic emissions of ozone precursors on ozone levels worldwide suggests further studies of the long-term effects of exposure to high ozone levels are warranted.
BackgroundFew European studies investigating associations between short-term exposure to air pollution and incident stroke have considered stroke subtypes. Using information from the South London ...Stroke Register for 2005–2012, we investigated associations between daily concentrations of gaseous and particulate air pollutants and incident stroke subtypes in an ethnically diverse area of London, UK.MethodsModelled daily pollutant concentrations based on a combination of measurements and dispersion modelling were linked at postcode level to incident stroke events stratified by haemorrhagic and ischaemic subtypes. The data were analysed using a time-stratified case–cross-over approach. Conditional logistic regression models included natural cubic splines for daily mean temperature and daily mean relative humidity, a binary term for public holidays and a sine–cosine annual cycle. Of primary interest were same day mean concentrations of particulate matter <2.5 and <10 µm in diameter (PM2.5, PM10), ozone (O3), nitrogen dioxide (NO2) and NO2+nitrogen oxide (NOX).ResultsOur analysis was based on 1758 incident strokes (1311 were ischaemic and 256 were haemorrhagic). We found no evidence of an association between all stroke or ischaemic stroke and same day exposure to PM2.5, PM10, O3, NO2 or NOX. For haemorrhagic stroke, we found a negative association with PM10 suggestive of a 14.6% (95% CI 0.7% to 26.5%) fall in risk per 10 µg/m3 increase in pollutant.ConclusionsUsing data from the South London Stroke Register, we found no evidence of a positive association between outdoor air pollution and incident stroke or its subtypes. These results, though in contrast to recent meta-analyses, are not inconsistent with the mixed findings of other UK studies.
Abstract Objective: To describe the incidence and prognosis of wheezing illness from birth to age 33 and the relation of incidence to perinatal, medical, social, environmental, and lifestyle factors. ...Design: Prospective longitudinal study. Setting: England, Scotland, and Wales. Subjects: 18 559 people born on 3-9 March 1958. 5801 (31%) contributed information at ages 7, 11, 16, 23, and 33 years. Attrition bias was evaluated using information on 14 571 (79%) subjects. Main outcome measure: History of asthma, wheezy bronchitis, or wheezing obtained from interview with subjects' parents at ages 7, 11, and 16 and reported at interview by subjects at ages 23 and 33. Results: The cumulative incidence of wheezing illness was 18% by age 7, 24% by age 16, and 43% by age 33. Incidence during childhood was strongly and independently associated with pneumonia, hay fever, and eczema. There were weaker independent associations with male sex, third trimester antepartum haemorrhage, whooping cough, recurrent abdominal pain, and migraine. Incidence from age 17 to 33 was associated strongly with active cigarette smoking and a history of hay fever. There were weaker independent associations with female sex, maternal albuminuria during pregnancy, and histories of eczema and migraine. Maternal smoking during pregnancy was weakly and inconsistently related to childhood wheezing but was a stronger and significant independent predictor of incidence after age 16. Among 880 subjects who developed asthma or wheezy bronchitis from birth to age 7, 50% had attacks in the previous year at age 7; 18% at 11, 10% at 16, 10% at 23, and 27% at 33. Relapse at 33 after prolonged remission of childhood wheezing was more common among current smokers and atopic subjects. Conclusion: Atopy and active cigarette smoking are major influences on the incidence and recurrence of wheezing during adulthood. Key messages Incidence of wheezing illness at all ages was strongly and consistently related to a history of hay fever or eczema (atopy). Associations with maternal smoking during pregnancy, abdominal pain, and migraine were largely confined to those without atopy Active smoking was a powerful and potentially avoidable risk factor for wheeze starting in adult life among both atopic and non-atopic subjects A quarter of the children with a history of asthma or wheezy bronchitis by age 7 reported wheeze in the past year at age 33 Recurrence of wheezing after prolonged remis- sion during late adolescence was strongly associ- ated with atopy and cigarette smoking.
Background There is much interest in reported associations between serum C-reactive protein and incident ischaemic heart disease. It is uncertain what this association represents. We aimed to assess ...the effect of confounding from a number of different sources in the Caerphilly Prospective Heart Disease Study and in particular whether the low grade inflammation indicated by C-reactive protein may be the mechanism whereby non-circulating risk factors may influence pathogenesis of ischaemic heart disease. Methods Plasma specimens collected during 1979–83 from 1395 men with sufficient sample remaining were assayed for serum C-reactive protein by ELISA. Subsequent mortality and incident ischaemic heart disease events were ascertained from death certificates, hospital records and electrocardiographic changes at 5-yearly follow-up examinations. Results There was a positive association between C-reactive protein and incident ischaemic heart disease (P<0·005) mainly with fatal disease (P<0·002). There was also a positive association with all-cause mortality (P<0·0001). C-reactive protein was significantly associated with a number of non-circulating risk factors including body mass index (P<0·0001), smoking (P<0·0001), low forced expiratory volume in 1s (P<0·0001), height (P=0·025), low childhood social class (P=0·014) and age (P=0·036). C-reactive protein was also associated positively with circulating risk factors including viscosity, leukocyte count, fibrinogen (all P<0·0001) and insulin (P=0·0058). After adjustment for non-circulating risk factors the association with all-incident ischaemic heart disease and ischaemic heart disease death became non-significant, but the association with all-cause mortality remained (P=0·033). Further adjustment for fibrinogen however removed any hint of an increasing trend in odds for all three outcomes. Conclusion C-reactive protein levels are raised in association with a variety of established cardiovascular risk factors. Neither C-reactive protein nor the systemic inflammation it represents appears to play a direct role in the development of ischaemic heart disease.
BACKGROUND A prospective cohort study of 2512 Welshmen aged 45–59 living in Caerphilly in 1979–1983 was used to investigate associations between diet and lung function. METHODS At baseline (phase I) ...and at five year follow up (phase II), forced expiratory volume in one second (FEV1) was measured using a McDermott spirometer and dietary data were obtained using a semi-quantitative food frequency questionnaire. RESULTS Good lung function, indicated by high maximum FEV1 given age and height, was associated with high intakes of vitamin C, vitamin E, β-carotene, citrus fruit, apples, and the frequent consumption of fruit juices/squashes. Lung function was inversely associated with magnesium intake but there was no evidence of an association with fatty fish. Following adjustment for confounders including body mass index, smoking history, social class, exercise, and total energy intake, only the associations with vitamin E and apples persisted, with lung function estimated to be 39 ml (95% confidence interval (CI) 9 to 69) higher for vitamin E intakes one standard deviation (SD) apart and 138 ml higher (95% CI 58 to 218) for those eating five or more apples per week compared with non-consumers. Decline in lung function between phases was not significantly associated with the changing intakes of apples or vitamin E. An association between high average apple consumption and slow decline in lung function lost significance after adjustment for confounders. CONCLUSIONS A strong positive association is seen between lung function and the number of apples eaten per week cross sectionally, consistent with a protective effect of hard fruit rather than soft/citrus fruit. The recent suggestion that such effects are reversible was not supported by our longitudinal analysis.
Abstract Objective: To investigate whether changes in certain perinatal and social factors explain the increased prevalence of hay fever and eczema among British adolescents between 1974 and 1986. ...Design: Two prospective birth cohort studies. Setting: England, Wales, and Scotland. Subjects: 11 195 children born 3-9 March 1958 and 9387 born 5-11 April 1970. Main outcome measures: Parental reports of eczematous rashes and of hay fever or allergic rhinitis in the previous 12 months at age 16. Results: The prevalence of the conditions over the 12 month period increased between 1974 and 1986 from 3.1% to 6.4% (prevalence ratio 2.04 (95% confidence interval 1.79 to 2.32) for eczema and from 12.0% to 23.3% (prevalence ratio 1.93 (1.82 to 2.06)) for hay fever. Both conditions were more commonly reported among children of higher birth order and those who were breast fed for longer than 1 month. Eczema was more commonly reported among girls and hay fever among boys. The prevalence of hay fever decreased sharply between social classes I and V, increased with maternal age up to the early 30s, and was lower in children whose mothers smoked during pregnancy. Neither condition varied significantly with birth weight. When adjusted for these factors, the relative odds of hay fever (1986 v 1974) increased from 2.23 (2.05 to 2.43) to 2.40 (2.19 to 2.63). Similarly, the relative odds of eczema rose from 2.02 (1.73 to 2.36) to 2.14 (1.81 to 2.52). Conclusions: Taken together, changes between cohorts in sex, birth weight, birth order, maternal age, breast feeding, maternal smoking during pregnancy, and father's social class at birth did not seem to explain any of the observed rise in the prevalence of hay fever and eczema. However, correlates of these factors which have changed over time may still underlie recent increases in allergic disease. Key messages Between 1974 and 1986 there was an apparent doubling in the 12 month period prevalence of both hay fever and eczema among British 16 year olds The prevalence of hay fever increased significantly with higher social class and decreasing birth order, both trends being steeper for children born in 1958 than for those born in 1970 Hay fever was less common if the mother smoked during pregnancy and more common with increasing maternal age up to the early 30s. The prevalences of hay fever and eczema were slightly higher among children breast fed for more than one month When taken together, differences in sex, birth weight, birth order, maternal age, breast feeding, maternal smoking during pregnancy, and father's social class at birth between children born in 1958 and those born in 1970 did not seem to explain any of the observed increases in prevalence of hay fever and eczema at age 16 Factors related to father's social class at birth, birth order, maternal age, smoking during pregnancy, and breast feeding deserve further investigation as possible explanations of the increase in atopic disease in Britain and elsewhere
Background: Uncontrolled studies suggest that psychosocial factors and health behaviour may be important in asthma death. Methods: A community based case-control study of 533 cases, comprising 78% of ...all asthma deaths under age 65 years and 533 hospital controls individually matched for age, district and asthma admission date corresponding to date of death was undertaken in seven regions of Britain (1994–98). Data were extracted blind from anonymised copies of primary care records for the previous 5 years and non-blind for the earlier period. Results: 60% of cases and 63% of controls were female. The median age in both groups was 53. Cases had an earlier age of asthma onset, more chronic obstructive lung disease, and were more obese. 48% of cases and 42% of controls had a health behaviour problem; repeated non-attendance/poor inhaler technique was related to increased risk of death. Overall, 85% and 86%, respectively, had a psychosocial problem. Four psychosocial factors were associated with increased risk of death (psychosis, alcohol/drug abuse, financial/employment problems, learning difficulties) and two with reduced risk (anxiety/prescription of antidepressant drugs and sexual problems). While alcohol/drug abuse lost significance after adjustment for psychosis, other associations appeared independent of each other and of indicators of severity and co-morbidity. None of the remaining 13 factors including family problems, domestic abuse, bereavement, and social isolation were significantly related to risk of asthma death. Conclusion: There was an apparently high burden of psychosocial problems in both cases and controls. The associations between health behaviour, psychosocial factors, and asthma death are varied and complex with a limited number of factors showing positive relationships.
Recent research has suggested an association between circulating C-reactive protein (CRP) and adult asthma, confined to those without evidence of allergic predisposition. The current authors ...investigated the role of smoking and obesity as possible explanations for this relationship. At 44-45 yrs of age, members of the British 1958 birth cohort participated in a biomedical survey involving the measurement of the following: CRP; the specific immunoglobulin E to grass, cat and dust mite; standing height; and weight. Information on asthma and related symptoms was collected by computer-aided interview when the subjects were 42 yrs of age. Complete data were available for a total of 6,490 subjects. CRP levels were positively correlated with the body mass index (BMI) and were found to be higher among females when compared with males, and higher among heavy smokers (> or = 20 cigarettes x day(-1)) when compared with never-smokers. After adjustment for sex and region, the odds ratios, comparing asthma prevalence in subjects above the fourth CRP quartile with subjects below the first quartile, were 1.85 (95% confidence interval 1.15-2.99) for nonatopics and 0.94 (0.62-1.41) for atopics, changing to 1.36 (0.80-2.32) and 1.07 (0.67-1.69), respectively, when additionally adjusted for smoking and BMI. Any association between C-reactive protein and asthma prevalence confined to nonatopics may be due to confounding factors. Alternatively, it may reflect a more general association of C-reactive protein with smoking-related obstructive airways disease.
Background: Studies have linked asthma death to either increased or decreased use of medical services. Methods: A population based case-control study of asthma deaths in 1994–8 was performed in 22 ...English, six Scottish, and five Welsh health authorities/boards. All 681 subjects who died were under the age of 65 years with asthma in Part I on the death certificates. After exclusions, 532 hospital controls were matched to 532 cases for age, district, and date of asthma admission/death. Data were extracted blind from primary care records. Results: The median age of the subjects who died was 53 years; 60% of cases and 64% of controls were female. There was little difference in outpatient attendance (55% and 55%), hospital admission for asthma (51% and 54%), and median inpatient days (20 days and 15 days) in the previous 5 years. After mutual adjustment and adjustment for sex, using conditional logistic regression, three variables were independently associated with asthma death: fewer general practice contacts (odds ratio 0.82 (95% confidence interval (CI) 0.74 to 0.91) per 5 contacts) in the previous year, more home visits (1.14 (95% CI 1.08 to 1.21) per visit) in the previous year, and fewer peak expiratory flow recordings (0.83 (95% CI 0.74 to 0.92) per occasion) in the previous 3 months. These associations were similar after adjustment for markers of severity, psychosocial factors, systemic steroids, short acting bronchodilators and antibiotics, although the association with peak flow was weakened and just lost significance. Conclusion: Asthma death is associated with less use of primary care services. Both practice and patient factors may be involved and a better understanding of these may offer possibilities for reducing asthma death.
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