Henriette A. Smit

Air pollution and development of asthma, allergy and infections in a birth cohort

Few studies have addressed associations between traffic-related air pollution and respiratory disease in young children. The present authors assessed the development of asthmatic/allergic symptoms and respiratory infections during the first 4 yrs of life in a birth cohort study (n = ∼4,000). Outdoor concentrations of traffic-related air pollutants (nitrogen dioxide PM2.5, particles with a 50% cut-off aerodynamic diameter of 2.5 μm and soot) were assigned to birthplace home addresses with a land-use regression model. They were linked by logistic regression to questionnaire data on doctor-diagnosed asthma, bronchitis, influenza and eczema and to self-reported wheeze, dry night-time cough, ear/nose/throat infections and skin rash. Total and specific immunoglobulin (Ig)E to common allergens were measured in a subgroup (n = 713). Adjusted odds ratios (95% confidence intervals) per interquartile pollution range were elevated for wheeze (1.2 (1.0–1.4) for soot), doctor-diagnosed asthma (1.3 (1.0–1.7)), ear/nose/throat infections (1.2 (1.0–1.3)) and flu/serious colds (1.2 (1.0–1.4)). No consistent associations were observed for other end-points. Positive associations between air pollution and specific sensitisation to common food allergens (1.6 (1.2–2.2) for soot), but not total IgE, were found in the subgroup with IgE measurements. Traffic-related pollution was associated with respiratory infections and some measures of asthma and allergy during the first 4 yrs of life.

Traffic-related Air Pollution and the Development of Asthma and Allergies during the First 8 Years of Life

RATIONALE The role of air pollution exposure in the development of asthma, allergies, and related symptoms remains unclear, due in part to the limited number of prospective cohort studies with sufficiently long follow-ups addressing this problem. OBJECTIVES We studied the association between traffic-related air pollution and the development of asthma, allergy, and related symptoms in a prospective birth cohort study with a unique 8-year follow-up. METHODS Annual questionnaire reports of asthma, hay fever, and related symptoms during the first 8 years of life were analyzed for 3,863 children. At age 8, measurements of allergic sensitization and bronchial hyperresponsiveness were performed for subpopulations (n = 1,700 and 936, respectively). Individual exposures to nitrogen dioxide (NO(2)), particulate matter (PM(2.5)), and soot at the birth address were estimated by land-use regression models. Associations between exposure to traffic-related air pollution and repeated measures of health outcomes were assessed by repeated-measures logistic regression analysis. Effects are presented for an interquartile range increase in exposure after adjusting for covariates. MEASUREMENTS AND MAIN RESULTS Annual prevalence was 3 to 6% for asthma and 12 to 23% for asthma symptoms. Annual incidence of asthma was 6% at age 1, and 1 to 2% at later ages. PM(2.5) levels were associated with a significant increase in incidence of asthma (odds ratio [OR], 1.28; 95% confidence interval [CI], 1.10-1.49), prevalence of asthma (OR, 1.26; 95% CI, 1.04-1.51), and prevalence of asthma symptoms (OR, 1.15; 95% CI, 1.02-1.28). Findings were similar for NO(2) and soot. Associations were stronger for children who had not moved since birth. Positive associations with hay fever were found in nonmovers only. No associations were found with atopic eczema, allergic sensitization, and bronchial hyperresponsiveness. CONCLUSIONS Exposure to traffic-related air pollution may cause asthma in children.

Cohort Profile: The Doetinchem Cohort Study

How did the study come about? The origin of the Doetinchem Cohort Study lies within the Monitoring Project on Cardiovascular Disease Risk Factors (MP-CVDRF), which was aimed at providing prevalence estimates of cardiovascular disease risk factors, such as smoking, blood pressure and serum cholesterol levels. During 1987–91 each year an age-and sex-stratified random sample of men and women aged 20–59 years, was invited to participate. The MP-CVDRF was carried out in three towns in The Netherlands (Amsterdam in the west, Doetinchem in the east and Maastricht in the south), and from each of the three towns, about 12 000 men and women were examined. In the subsequent Monitoring Project on Chronic Disease Risk Factors (MORGEN-project), carried out from 1993–97, in Doetinchem only respondents from the MP-CVDRF were invited to participate, while in Amsterdam and Maastricht again random samples from the general population were examined. The protocol was extended, because the focus broadened from cardiovascular to other chronic diseases such as cancer, diabetes, musculoskeletal disorders and COPD. Due to extension of the protocol, with similar budget, not all 12 405 participants in the MP-CVDRF could be re-invited. Instead, a random sample of in total 7769 of the respondents at baseline was invited for re-examination. This random sample is considered the basis of the cohort (Figure 1). The aim of the Doetinchem Cohort Study is to study the impact of (changes in) lifestyle factors and biological risk factors on aspects of health, such as the incidence of chronic diseases, physical and cognitive functioning and quality of life. During the course of the study, the scope has continuously broadened. At baseline, the focus was on determinants of cardiovascular diseases. Starting from the second examination of the cohort, the scope has extended to a broad spectrum of chronic diseases that have a substantial public health impact, such as diabetes, cancer, musculoskeletal disorders, asthma and COPD. During the fourth round the social aspects were assessed and in the fifth round that will start in 2008 the focus will be more on healthy ageing and the measures will also include bone density, osteoarthri-tis, osteoporosis and fractures, other chronic diseases than the big five (such as diseases of bowel, liver, thyroid gland), incontinence, muscle strength and tests for physical functioning. The study is thus aimed at a broad spectrum of hypotheses, with respect to both exposure and outcomes (Table 1). A biobank, with blood samples from each …

Association of consumption of products containing milk fat with reduced asthma risk in pre-school children: the PIAMA birth cohort study

Background: Environment and lifestyle contribute to the development of asthma in children. Understanding the relevant factors in this relationship may provide methods of prevention. The role of diet in the development of asthma in pre-school children was investigated. Methods: Data from 2978 children participating in a prospective birth cohort study were used. Food frequency data were collected at the age of 2 years and related to asthma symptoms reported at the age of 3 years. Results: The prevalence of recent asthma at age 3 was lower in children who consumed (at age 2) full cream milk daily (3.4%) than in those who did not (5.6%) and in those who consumed butter daily (1.5%) than in those who did not (5.1%). The prevalence of recent wheeze was lower in children who consumed milk products daily (13.7%) than in those who did not (18.4%) and in children who consumed butter daily (7.7%) than in those who did not (15.4%). These effects remained in a logistic regression model including different foods and confounders (adjusted odds ratio (CI) for recent asthma: full cream milk daily v rarely 0.59 (0.40 to 0.88), butter daily v rarely 0.28 (0.09 to 0.88)). Daily consumption of brown bread was also associated with lower rates of asthma and wheeze, whereas no associations were observed with the consumption of fruits, vegetables, margarine, and fish. Conclusions: In pre-school children, frequent consumption of products containing milk fat is associated with a reduced risk of asthma symptoms.

Dietary influences on chronic obstructive lung disease and asthma: a review of the epidemiological evidence

The epidemiological evidence for a relationship between diet and indicators of asthma and chronic obstructive pulmonary disease (COPD) is evaluated. The review focuses on the intake of Na, n-3 fatty acids, and antioxidant vitamins as well as fruit and vegetables. Experimental studies suggest that a high-Na diet has a small adverse effect on airway reactivity in asthma patients. However, observational studies provide no clear evidence that high Na intake has adverse effects on airway reactivity or asthma symptoms in open populations. n-3 Polyunsaturated fatty acids, which are present in fish oils, are metabolized into less broncho-constricting and inflammatory mediators than n-6 polyunsaturated fatty acids. Studies in the general adult population suggest that a high fish intake has a beneficial effect on lung function, but the relationship with respiratory symptoms and clinically-manifest asthma or COPD is less evident. Also, experimental studies in asthma patients have not demonstrated an improvement in asthma severity after supplementations with fish oil. Several studies showed a beneficial association between fruit and vegetable intake and lung function, but the relationship with respiratory symptoms and the clinically-manifest disease was less convincing. A similar pattern was found for vitamin C in relation to indicators of asthma and COPD, but there are still conflicting results with respect to vitamin E and beta-carotene. In conclusion, the epidemiological evidence for a beneficial effect on indicators of asthma and COPD of eating fish, fruit and vegetables is increasing. However, the effectiveness of dietary supplementation in open-population samples is often not demonstrated. Several unresolved questions are raised, which should be addressed in future studies on the relationship between diet and respiratory disease.

Asthma at 8 years of age in children born by caesarean section

Background: Caesarean section might be a risk factor for asthma because of delayed microbial colonisation, but the association remains controversial. A study was undertaken to investigate prospectively whether children born by caesarean section are more at risk of having asthma in childhood and sensitisation at the age of 8 years, taking into account the allergic status of the parents. Methods: 2917 children who participated in a birth cohort study were followed for 8 years. The definition of asthma included wheeze, dyspnoea and prescription of inhaled steroids. In a subgroup (n = 1454), serum IgE antibodies for inhalant and food allergens were measured at 8 years. Results: In the total study population, 12.4% (n = 362) of the children had asthma at the age of 8 years. Caesarean section, with a total prevalence of 8.5%, was associated with an increased risk of asthma (OR 1.79; 95% CI 1.27 to 2.51). This association was stronger among predisposed children (with two allergic parents: OR 2.91; 95% CI 1.20 to 7.05; with only one: OR 1.86; 95% CI 1.12 to 3.09) than in children with non-allergic parents (OR 1.36; 95% CI 0.77 to 2.42). The association between caesarean section and sensitisation at the age of 8 years was significant only in children of non-allergic parents (OR 2.14; 95% CI 1.16 to 3.98). Conclusions: Children born by caesarean section have a higher risk of asthma than those born by vaginal delivery, particularly children of allergic parents. Caesarean section increases the risk for sensitisation to common allergens in children with non-allergic parents only.

Diet and chronic obstructive pulmonary disease: independent beneficial effects of fruits, whole grains, and alcohol (the MORGEN study)

Background In recent years antioxidants, foods rich in antioxidants (e.g. fruits, vegetables) and fish have been suggested to protect against chronic obstructive pulmonary disease (COPD). There are also indications for a protective effect of whole grain intake and of consuming moderate amounts of alcohol. It is, however, not clear whether the effects of the different dietary factors on COPD are independent of each other and if so, whether their effects are additive.

Dietary factors and pulmonary function: a cross sectional study in middle aged men from three European countries

BACKGROUND Results of epidemiological studies relating individual dietary factors to chronic obstructive pulmonary disease (COPD) are inconsistent. To evaluate the cross sectional association of dietary factors with pulmonary function, data were collected from middle aged men in three European countries. METHODS The data were collected in the 1960s in Finland (n = 1248), Italy (n = 1386), and the Netherlands (n = 691). Dietary intake was estimated using the cross-check dietary history method. Forced expiratory volume (FEV0.75 or FEV1, here called FEV) was measured by spirometry. Associations were adjusted for age, height, smoking, body mass index (BMI), alcohol consumption, and energy intake. RESULTS FEV was positively associated with intake of vitamin E in Finland, with intake of fruit in Italy, and with intake of β-carotene in the Netherlands. In all three countries men with intakes of both fruit and vegetables above the median had a higher FEV than those with a low intake of both foods. The difference in FEV ranged from 110 to 169 ml before and from 53 to 118 ml after energy adjustment. Differences in FEV for intake of three antioxidants (vitamins C and E and β-carotene) above versus below the median ranged from 61 to 181 ml before and from –35 to 58 ml after energy adjustment. Intake of fish was not associated with FEV. CONCLUSIONS In three European countries a high intake of fruit and vegetables was positively associated with pulmonary function. A high intake of all three antioxidants tended to be positively associated with pulmonary function before, but not after, adjustment for energy intake. Associations of individual antioxidants with pulmonary function were not consistent across countries.

Maternal Food Consumption during Pregnancy and the Longitudinal Development of Childhood Asthma

RATIONALE Maternal diet during pregnancy has the potential to affect airway development and to promote T-helper-2-cell responses during fetal life. This might increase the risk of developing childhood asthma or allergy. OBJECTIVES We investigated the influence of maternal food consumption during pregnancy on childhood asthma outcomes from 1 to 8 years of age. METHODS A birth cohort study consisting of a baseline of 4,146 pregnant women (1,327 atopic and 2,819 nonatopic). These women were asked about their frequency of consumption of fruit, vegetables, fish, egg, milk, milk products, nuts, and nut products during the last month. Their children were followed until 8 years of age. Longitudinal analyses were conducted to assess associations between maternal diet during pregnancy and childhood asthma outcomes over 8 years. MEASUREMENTS AND MAIN RESULTS Complete data were obtained for 2,832 children. There were no associations between maternal vegetable, fish, egg, milk or milk products, and nut consumption and longitudinal childhood outcomes. Daily consumption of nut products increased the risk of childhood wheeze (odds ratio [OR] daily versus rare consumption, 1.42; 95% confidence interval [95% CI], 1.06-1.89), dyspnea (OR, 1.58; 95% CI, 1.16-2.15), steroid use (OR, 1.62; 95% CI, 1.06-2.46), and asthma symptoms (OR, 1.47; 95% CI, 1.08-1.99). CONCLUSIONS Results of this study indicate an increased risk of daily versus rare consumption of nut products during pregnancy on childhood asthma outcomes. These findings need to be replicated by other studies before dietary advice can be given to pregnant women.

Overweight and changes in weight status during childhood in relation to asthma symptoms at 8 years of age.

BACKGROUND Asthma may be more prevalent in overweight children. However, how early overweight and changes in weight status during childhood affect the asthma risk is unclear. OBJECTIVES To investigate overweight and changes in overweight status in children age 1 to 8 years in relation to asthma symptoms in childhood. METHODS We studied 3756 children who participated in a large birth cohort study. The parents reported their childrens weight and height, and wheeze, dyspnea, and prescription of inhaled corticosteroids in yearly questionnaires. Sensitization to inhalant allergens and bronchial hyperresponsiveness (BHR) were determined at 8 years. RESULTS At 8 years, 275 children (7.3%) wheezed, 361 (9.6%) had dyspnea, and 268 (7.1%) had a prescription of inhaled corticosteroids in the preceding year. Children who had a persistent high body mass index (BMI, weight/height2) during childhood or a high BMI at 6 to 7 years had a significantly increased risk of dyspnea (adjusted odds ratio, 1.68; 95% CI, 1.18-2.39, for a high BMI at 6-7 years) and measured BHR (adjusted odds ratio, 1.66; 95% CI, 1.10-2.52) at 8 years. Children with a high BMI at a young age, but who developed a normal BMI at 6 to 7 years, did not have an increased risk of dyspnea or BHR at 8 years. BMI was not associated with sensitization. CONCLUSION Children with a current high BMI are at increased risk to have dyspnea and BHR at 8 years. A high BMI at an earlier age is not related to an increased risk if the child has become normal weight at 6 to 7 years.