The incidence of atopic disease and its relation to the family history was studied by questionnaire in 1325 children, 7 years of age. A higher incidence of bronchial asthma (2.7%) was found than in a previous Swedish study. The total incidence of atopic disease in the children was 15.1% with a higher level when there was a double parental history of such disease (42.6%) as compared with a single such history (19.8%). When both parents had an identical type of atopic disease, i.e. respiratory or skin, the incidence of atopic disease was higher (72.2%) than when non-identical types occurred in the parents (20.8%). The findings support theories of a polygenic transmission of atopic disease as well as a genetic influence on symptom specificity in such disease and may be of value in genetic counselling.
AIM: It has been suggested that living on a farm decreases the risk of childhood allergy, especially if farming involves livestock. The aim of this study was to examine the association between farming and allergy in children, and the influence of atopic heredity in this association. METHODS: The cross-sectional data of the 7981 children aged 13-14 y who participated in the Finnish ISAAC study between the years 1994 and 1995 were used to evaluate the association between farming and allergy. RESULTS: Living on a farm was associated with a decreased risk of current symptoms of allergic rhinoconjunctivitis among all children (aOR 0.79; 95% CI 0.63, 0.99), and with a decreased risk of hay fever, especially among those children with a parental history of hayfever (aOR 0.60; 95% CI 0.40-0.89, p = 0.072 for interaction). The children of farmers with a history of hay fever also had a decreased risk of current wheeze (aOR 0.38; 95% CI 0.12-1.24, p = 0.040 for interaction). No significant association was found between farming and either asthma or eczema. Children living on a farm with livestock had the lowest risk of allergic rhinoconjunctivitis (aOR 0.69), followed by those living on a farm without livestock (aOR 0.89) compared with the non-farming children (p-value for trend 0.024). CONCLUSION: Our results support the recent findings on a decreased risk of allergy among the children living on farms. A possible differential effect of parental history of hay fever on the relation of farming environment and the risk of allergic symptoms warrant further investigation.
Cumulative life prevalence of atopic disease (any of reported symptoms of asthma/wheezy bronchitis, allergic rhinitis, eczema and urticaria) was studied by means of a questionnaire in 19814 (7-, 10- and 14-year-old) Swedish school children and their parents. Maternal history was found to be twice as common as paternal history. The children of affected mothers contracted atopic disease in the same proportion as the children of affected fathers yielding twice as many affected children with affected mothers than with affected fathers. The strongest parental influence on childhood disease was seen for multiple symptoms and for congruent symptoms with both parents. The number of children with both parents affected was 1.6 times larger than expected. A possible dose-response effect in polygenic inheritance is discussed as well as assumed impact of environmental factors with a tendency to familial clustering.
Various atopic manifestations among adults have been shown to be influenced mainly by genetic factors. With the increase in prevalence of atopic diseases in recent years, especially among children, a great deal of attention has been given to environmental causes. In a study of 1480 Swedish twin pairs, 7-9 years old, we examined the importance of genetic and environmental factors in asthma, hay fever, eczema, and urticaria. Structural equation model fitting showed 33-76% of the variation in liability to the diseases to be due to genetic effects. Shared environmental effects were also important for hay fever and urticaria in both sexes and for eczema among girls. The clustering of atopic disease in families was almost entirely due to a common set of genes, but each disease manifestation also seemed to have specific genes of importance. Investigation of unlike-sex twins showed that boys had a higher cumulative incidence of asthma and hay fever than girls, whereas girls had a higher incidence of eczema. Thus, it may be concluded that although genetic factors are of major importance in atopic manifestation in children, both environmental and sex-related factors play a role.
Like other atopic diseases, hay fever is known to cluster in families. This clustering is due either to effects of a shared family environment or to genetic inheritance. By comparing the occurrence of hay fever among monozygous (MZ) and dizygous (DZ) twin pairs, we were able to estimate the contribution of genetic and environmental factors in the development of hay fever.
A questionnaire mailed to a nationwide sample of 2483 families with 16-year-old twins furnished data for the cumulative incidence of physician-diagnosed hay fever among these adolescents and their parents.
Among the 1765 twin pairs with data available for analysis, hay fever was reported for 14.1% of boys (95% CI=12.4-15.8%) and 10.0% of girls (95% CI=8.6-11.4%). The MZ twin pairs (probandwise concordance rate=60.3%, 95% CI =52-68%) were significantly more concordant for hay fever than were DZ twin pairs (31.5%, 95% CI=26-36%). Genetic factors accounted for 74-82% of the interindividual variability in liability to hay fever, variation in shared family environment for 7% at most, and unique (individual) environment for 18%.
Familial occurrence of hay fever is mainly due to genes predisposing to the trait. Environmental exposures shared in common by family members but varying between families appear to account for at most a modest proportion of the variability in risk of developing hay fever.
Vitamin D is known to have a number of immunological effects and it may play a role in preventing allergic diseases. Objectives To study the effect of maternal intake of vitamin D during pregnancy on the emergence of asthma, allergic rhinitis (AR), and atopic eczema by the age of 5 years in children with HLA-DQB1-conferred susceptibility for type 1 diabetes.
Children (1669) participating in the population-based birth cohort study were followed for asthma, AR, and atopic eczema assessed by validated questionnaire at 5 years. Maternal diet was assessed by a food-frequency questionnaire.
The mean maternal intake of vitamin D was 5.1 (SD 2.6) microg from food and 1.4 (2.6) microg from supplements. Only 32% of the women were taking vitamin D supplements. When adjusted for potential confounders, maternal intake of vitamin D from food was negatively related to risk of asthma [hazard ratio (HR) 0.80; 95% confidence interval (CI) 0.64-0.99] and AR [HR 0.85; 95% CI 0.75-0.97]. Vitamin D supplements alone were not associated with any outcome. Adjustment for maternal intake of other dietary factors did not change the results.
Maternal vitamin D intake from foods during pregnancy may be negatively associated with risk of asthma and AR in childhood.