Barbara K Butland

Trends in prevalence and severity of childhood asthma.

Abstract Objective: To test the null hypothesis and there has been no change in the prevalence or severity of childhood asthma over recent years. Design: Repeated population prevalence survey with questionnaires completed by parents followed by home interviews with parents. Setting: London borough of Croydon, 1978 and 1991. Subjects: All children in one year of state and private primary schools aged 7 1/2 to 8 1/2 years at screening survey. Main outcome measures: Trends in symptoms, acute severe attacks, and chronic disability. Results: For 1978 and 1991 respectively, the response rates were 4147/4763 and 3070/3786, and home interviews were obtained from 273/288 and 319/395 parents of currently wheezy children. Between 1978 and 1991 there were significant relative increases in prevalence ratios in the 12 month prevalence of attacks of wheezing or asthma (1.16; 95% confidence interval 1.02 to 1.31), the one month prevalence of wheezing episodes (1.78, 1.15 to 2.74), and the one month prevalence of night waking (1.81; 1.01 to 3.23) but not in frequent (>=5) attacks over the past year (1.05; 0.79 to 1.40). There were substantial and significant decreases in the 12 months prevalence of absence from school of more than 10 days due to wheezing (0.52; 0.03 to 0.90), any days in bed (0.67; 0.44 to 1.01), and restriction of activities at home (0.51; 0.31 to 0.83) and an equivalent but not significant fall in speech limiting attacks (0.51; 0.24 to 1.11). Conclusion: The small increase in the prevalence of wheezy children and relatively greater increase in persistent wheezing suggests a change in the environmental determinants of asthma. In contrast and paradoxically the frequency of wheezing attacks remains unchanged and there are indications that severe attacks and chronic disability have fallen by about half; this may be due to an improvement in treatment received by wheezy children.

Investigation into the increase in hay fever and eczema at age 16 observed between the 1958 and 1970 British birth cohorts

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 fathers 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 fathers 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 fathers 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

Diet, lung function, and lung function decline in a cohort of 2512 middle aged men

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.

Bronchodilator treatment and deaths from asthma: case-control study

Abstract Objective To investigate the association between bronchodilator treatment and death from asthma. Design Case-control study. Setting 33 health authorities or health boards in Great Britain. Participants 532 patients under age 65 who died from asthma and 532 controls with a hospital admission for asthma matched for period, age, and area. Main outcome measures Odds ratios for deaths from asthma associated with prescription of bronchodilators and other treatment, with sensitivity analyses adjusting for age at onset, previous hospital admissions, associated chronic obstructive lung disease, and number of other drug categories. Results After full adjustment, there were no significant associations with drugs prescribed in the 4-12 months before the index date. For prescriptions in the 1-5 years before, mortality was positively associated with inhaled short acting β2 agonists (odds ratio 2.05, 95% confidence interval 1.26 to 3.33) and inversely associated with antibiotics (0.59, 0.39 to 0.89). The former association seemed to be confined to those aged 45-64, and the association with antibiotics was more pronounced in those under 45. Significant age interactions across all periods suggested inverse associations with oral steroids confined to the under 45 age group. An inverse association with long acting β2 agonists and a positive association with methylxanthines in the 1-5 year period were non-significant. Conclusion There was no evidence of adverse effects on mortality with medium to long term use of inhaled long acting β2 agonist drugs. The association with short acting β2 agonists has several explanations, only one of which may be a direct adverse effect.

Study of the aetiology of wheezing illness at age 16 in two national British birth cohorts.

BACKGROUND: Data from two national British birth cohorts were used to measure the increase in prevalence of wheezing illness at age 16 between 1974 and 1986, and to investigate the role of several potential risk factors in the increase. METHODS: The occurrence of self-reported asthma or wheezy bronchitis within the past year, and the frequency of attacks of wheezing illness at age 16, were compared in 11,262 and 9266 children born in one week of 1958 and 1970, respectively. The effects of several putative risk factors for asthma--including birth weight, maternal age, birth order, breast feeding, maternal smoking in pregnancy, childs personal smoking, and fathers social class--on the change in occurrence of wheezing illness at age 16 were assessed by multiple logistic regression. RESULTS: The annual period prevalence of asthma or wheezy bronchitis at age 16 increased from 3.8% in 1974 to 6.5% in 1986 (prevalence ratio (PR) = 1.71, 95% CI 1.52 to 1.93). The proportion of children experiencing attacks more than once a week increased from 0.2% to 0.7% (PR = 3.77, 95% CI 2.28 to 6.23). The prevalence of self-reported eczema and hayfever within the past year doubled between 1974 and 1986, suggesting that the increase in asthma was part of a general increase in the prevalence of atopic disease. However, in the complete dataset, after adjustment for the effects of the risk factors studied, the prevalence odds ratio for asthma or wheezy bronchitis in 1986 compared with 1974 was virtually unchanged from the unadjusted value at 1.77 (95% CI 1.46 to 2.15). CONCLUSION: The prevalence of wheezing illness in British teenagers increased by approximately 70% between 1974 and 1986. This increase appears to have occurred in the context of a general increase in atopic disease and was largely unexplained by changes in the distribution of maternal age, birth order, birth weight, infant feeding, maternal smoking, active smoking by the child, or fathers social class.

Psychological, social and health behaviour risk factors for deaths certified as asthma: a national case-control study

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.

Alcohol and high-density-lipoprotein cholesterol: a randomized controlled trial

1. A randomized controlled trial of cross-over design was set up to examine the effect of alcohol on blood lipids and certain haematological variates relevant to ischaemic heart disease. 2. One hundred subjects drank some alcohol for 4 weeks (mean intake 18.4 g/d) and abstained totally for 4 weeks, the order of these periods being randomized. 3. Alcohol appeared to produce a rise of 7% in serum high-density-lipoprotein (HDL) cholesterol, probably due to a rise in the HDL2 subfraction. 4. No significant change was detected in plasma fibrinogen or the other haematological indices. 5. These results are consistent with the hypothesis that a moderate intake of alcohol confers some protection against heart disease.

Satellite-based Estimates of Ambient Air Pollution and Global Variations in Childhood Asthma Prevalence

Background: The effect of ambient air pollution on global variations and trends in asthma prevalence is unclear. Objectives: Our goal was to investigate community-level associations between asthma prevalence data from the International Study of Asthma and Allergies in Childhood (ISAAC) and satellite-based estimates of particulate matter with aerodynamic diameter < 2.5 µm (PM2.5) and nitrogen dioxide (NO2), and modelled estimates of ozone. Methods: We assigned satellite-based estimates of PM2.5 and NO2 at a spatial resolution of 0.1° × 0.1° and modeled estimates of ozone at a resolution of 1° × 1° to 183 ISAAC centers. We used center-level prevalence of severe asthma as the outcome and multilevel models to adjust for gross national income (GNI) and center- and country-level sex, climate, and population density. We examined associations (adjusting for GNI) between air pollution and asthma prevalence over time in centers with data from ISAAC Phase One (mid-1900s) and Phase Three (2001–2003). Results: For the 13- to 14-year age group (128 centers in 28 countries), the estimated average within-country change in center-level asthma prevalence per 100 children per 10% increase in center-level PM2.5 and NO2 was –0.043 [95% confidence interval (CI): –0.139, 0.053] and 0.017 (95% CI: –0.030, 0.064) respectively. For ozone the estimated change in prevalence per parts per billion by volume was –0.116 (95% CI: –0.234, 0.001). Equivalent results for the 6- to 7-year age group (83 centers in 20 countries), though slightly different, were not significantly positive. For the 13- to 14-year age group, change in center-level asthma prevalence over time per 100 children per 10% increase in PM2.5 from Phase One to Phase Three was –0.139 (95% CI: –0.347, 0.068). The corresponding association with ozone (per ppbV) was –0.171 (95% CI: –0.275, –0.067). Conclusion: In contrast to reports from within-community studies of individuals exposed to traffic pollution, we did not find evidence of a positive association between ambient air pollution and asthma prevalence as measured at the community level.

Deaths certified as asthma and use of medical services: a national case-control study

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.

Childhood asthma in South London: trends in prevalence and use of medical services 1991–2002

Background: Hospital admission rates for asthma in Britain rose during the 1980s and fell during the 1990s, but less is known about recent trends in the prevalence of asthma. Methods: In 1991 and 2002 the same questionnaire was distributed to parents of all school pupils in year 3 (aged 7–8 years) in the London borough of Croydon. Parents of currently wheezy children were then invited for home interview (100% targeted in 1991, 66% in 2002). Results: The prevalence of wheeze during the previous year increased from 12.9% in 1991 to 17.8% in 2002 (prevalence ratio 1.39 (95% CI 1.23 to 1.56)). Increases were observed in frequent (1.54 (95% CI 1.16 to 2.03)) and infrequent attacks, severe speech limiting episodes (2.25 (95% CI 1.34 to 3.77)), and night waking (1.36 (95% CI 1.07 to 1.72)), and in the reported use of steroids (19.9% v 64.1% of currently wheezy children). Nevertheless, the proportions reporting a visit to the GP at his/her surgery for wheeze in the previous year (prevalence ratio 1.15 (95% CI 0.91 to 1.45)) or an outpatient visit (0.98 (95% CI 0.49 to 1.94)) changed little and an increase in reported casualty attendance (1.66 (95% CI 0.89 to 3.07)) was non-significant. Conclusions: There is evidence of an increase in the prevalence of asthma among British primary school children between 1991 and 2002. The absence of a corresponding increase in health service utilisation data may reflect more widespread prophylactic treatment and/or changes in the use and provision of medical services.