Season of birth as predictor of atopic manifestations

The increase in allergic respiratory diseases: survival of the fittest?

The prevalence of allergic respiratory diseases, asthma and allergic rhinoconjunctivitis, has increased since the advent of industrialization. The inverse relationship between the number of infections early in life and atopy has been interpreted as the "hygiene hypothesis." That is, many infections early in life promote the development of T helper type 1 cytokines, while fewer infections early in life favor the development of T helper type 2 (Th2) cytokines and atopy. An alternate interpretation of the same data, that atopy is protective against infections early in life, is rarely considered. With epidemiologic, historical, and immunologic data, I suggest that human evolution has favored individuals with an atopic predisposition. Th2 immune responses promote parity, and ensure successful pregnancy and term birth; provide the infant protection against infections and the inflammation induced by common pathogens in the first years of life until the immune system matures; and protect young adults exposed to viral respiratory pathogens. These traits are of particular value with the advent of industrialization, especially so in the era prior to the development of antibiotics. This theory contradicts the assumption that there is no biological or evolutionary advantage for allergic disease to exist in humans and has significant implications for our current and future treatments of allergic diseases.

Wheezing following lower respiratory tract infections with respiratory syncytial virus and influenza A in infancy

We examined the incidence of subsequent wheezing in 292 children, hospitalized for influenza A or respiratory syncytial virus (RSV) lower respiratory tract infection, during two consecutive seasons (November-December, 1993 and March-April, 1995). Questionnaires concerning episodes of wheezing and known risk factors for wheezy bronchitis were mailed to parents 1 year after hospitalization. Sixty per cent of parents reported two or more episodes of wheezing following either influenza A or RSV. Hospitalization as a result of wheezing was necessary in 15% of the patients. The severity of the primary infection, as indicated by the need for treatment in the intensive care unit (ICU), was correlated with later wheezing. No additional significant risk factors predicting later wheezing could be identified.

Month of birth and risk of developing insulin dependent diabetes in south east Sweden

Environmental factors very early in life may be important for later development of insulin dependent diabetes. Because several of these factors, such as infections, vary with season, we predicted a difference in birth pattern compared with the general population among children who develop diabetes. In a population based study we analysed all 1248 children from seven paediatric departments in the south east part of Sweden to evaluate whether there is such a relation. There was a significant difference in birth pattern in patients with diabetes compared with the general population. Children who developed diabetes at the age of 10-15 years accounted for most of this difference. Boys had a more pronounced difference in birth pattern than girls. Children diagnosed with diabetes during years of high incidence, as well as children with an infection before diagnosis of diabetes, showed a significantly different birth pattern compared with the background population. These results indicate that there is a difference in birth pattern in children who develop diabetes compared with the background population. This supports the theory that environmental factors early in life play a role in the development of diabetes many years later.

Allergic disease in teenagers in relation to urban or rural residence at various stages of childhood

BACKGROUND

Higher prevalences of allergic diseases and IgE antibodies to inhalant allergens have been reported for persons living in urban areas than for persons living in rural areas.

METHODS

Associations between cumulative incidences of allergic diseases in 1878 children aged 13-14 years and their place of residence (urban, semiurban, or rural) from birth were assessed by questionnaire (ISAAC), in order to find out whether there is a period of increased sensitivity to external influences during the first few years of life. Family history and exposure to pets, tobacco smoke, and damp were considered in multiple regression.

RESULTS

There was a significantly higher prevalence of allergic diseases with urban residence than with rural residence during the first 2 years of life (e.g., for bronchial asthma, relative risk (RR) for the first year 2.1, 95% CI 1.2-3.7). An increased risk was still found after multiple regression (RR=1.7). Semiurban residence was associated with an intermediate cumulative incidence of allergic diseases. Maternal smoking during pregnancy was associated with asthma (RR=1.4, 95% CI 1.0-2.0).

CONCLUSIONS

The findings support a period of increased susceptibility during the first years of life. Whether rural lifestyle protects against allergy or whether urban pollutants contribute to allergy has to be elucidated [corrected].

Month of birth and prevalence of atopic dermatitis in schoolchildren: dry skin in early infancy as a possible etiologic factor

BACKGROUND

Month of birth has been shown to affect later development of allergic diseases.

OBJECTIVE

We sought to evaluate the relationship between month of birth and the prevalence of atopic dermatitis (AD) in a large-scale general population of schoolchildren and to elucidate the possible mechanism for this relationship.

METHODS

Questionnaire data on the prevalence of allergic diseases were obtained for 33,725 schoolchildren aged 7 to 15 years. In a separate study the water-holding capacity of "uninvolved" skin was compared for children with and without AD.

RESULTS

We found striking differences in the prevalence of AD according to the month of birth (chi2 = 34.9, P <.0001). Overall, those born in autumn showed the highest (7.5%), and those born in spring showed the lowest (5.5%), prevalence of AD. There was little or no such tendency for the prevalence of bronchial asthma (chi2 = 17.2, P =.103) and allergic rhinitis (chi2 = 24, P =.01). We found no statistical variation across birth month in the ratio of AD with no other allergic disease/total AD, indicating that this deviation was observed whatever the allergic predisposition of the subjects. In a separate study a significantly lower water-holding capacity of uninvolved skin was observed in children with AD even from early infancy.

CONCLUSION

These findings lead us to speculate that the climate in early infancy affects the skin condition and that those born in autumn have dry skin in early infancy, which may ultimately result in a higher prevalence of AD among young schoolchildren. This might be at least one of the "nonallergic" etiologic factors of this complex disease.

Relation between IgG antibodies to foods and IgE antibodies to milk, egg, cat, dog and/or mite in a cross-sectional study

BACKGROUND

Because IgG antibodies to foods can be detected before IgE antibodies to inhalants, increased levels of IgG antibodies to foods might be used as a predictor of IgE-mediated allergy in initially nonatopic children.

OBJECTIVE

To examine the cross-sectional relation between IgG to foods (i.e. mixture of wheat and rice, mixture of soybean and peanut, egg white, cow's milk, meat, orange and potato) and specific IgE to cat, dog, mite, milk and egg white in 1-year-old children.

METHODS

All atopic children (n = 120; 58 with and 62 without eczema) and a random sample of the nonatopic children (n = 144) of the Bokaal study were tested on their IgG response to foods. The IgG results of the food assays were dichotomized high or low using the 66th centile as a cut-off value.

RESULTS

Atopic children more often had high IgG levels to foods than nonatopic children. IgG to egg white (OR = 7.50) and mixture of wheat and rice (OR = 4.79) were most strongly associated with positive specific IgE. In a stepwise logistic regression analysis egg white, mixture of wheat and rice, and orange were selected (OR = 3.76, OR = 2.43, and OR = 2.11, respectively). In children without eczema higher levels of IgG to foods were still significantly associated with atopy, which was most prominent for egg white, orange and cow's milk.

CONCLUSION

An increased IgG antibody level to foods, especially to egg white, orange, and mixture of wheat and rice, indicates an increased risk of having IgE to cat, dog, mite, egg and/or milk allergens, even in the noneczematous group. Therefore, in another prospective study we are currently investigating the usefulness of IgG in early identification, i.e. before IgE antibodies can be detected, of children with an increased risk of developing allergic diseases in the future.

Does early exposure to cat or dog protect against later allergy development?

BACKGROUND

It is unknown which factors in modern western society that have caused the current increase in prevalence of allergic diseases. Improved hygiene, smaller families, altered exposure to allergens have been suggested.

OBJECTIVES

To assess the relationship between exposure to pets in early life, family size, allergic manifestations and allergic sensitization at 7-9 and 12-13 years of age.

METHODS

The prevalence of allergic diseases and various background factors were assessed in 1991 and 1996 by questionnaire studies. In 1991, the study comprised representative samples of children from the Göteborg area on the Swedish west coast (7 years old, n = 1649) and the inland town Kiruna in northern Sweden (7-9 years old, n = 832). In 1992, a validation interview and skin prick test (SPT) were performed in a stratified sub-sample of 412 children. In 1996, this subgroup was followed up with identical questions about clinical symptoms as in 1991, detailed questions about early pet exposure were added and SPT performed.

RESULTS

Children exposed to pets during the first year of life had a lower frequency of allergic rhinitis at 7-9 years of age and of asthma at 12-13 years. Children exposed to cat during the first year of life were less often SPT positive to cat at 12-13 years. The results were similar when those children were excluded, whose parents had actively decided against pet keeping during infancy because of allergy in the family. There was a negative correlation between the number of siblings and development of asthma and allergic rhinitis.

CONCLUSION

Pet exposure during the first year of life and increasing number of siblings were both associated with a lower prevalence of allergic rhinitis and asthma in school children.

Programming for responsiveness to environmental antigens that trigger allergic respiratory disease in adulthood is initiated during the perinatal period

Allergy to airborne environmental antigens (allergens) is a major cause of asthma in children and adults. This review argues that the development of allergen-specific immunologic memory of the type that predisposes to allergy development is the end result of a T-cell selection process operative during infancy, which is triggered via encounters between the immature immune system and incoming airborne allergens from the environment. In normal individuals this process leads to the development of allergen-specific T-memory cells that secure the T helper (Th)-1 pattern of cytokines, which actively suppress the growth of their allergy-inducing Th-2 cytokine-secreting counterparts. However, these protective allergen-reactive Th-1 memory cells fail to develop in some individuals, permitting the subsequent proliferation of allergen-specific Th-2 cells that can trigger allergic reactions. Recent evidence suggests that genetic predisposition to allergy may be due in part to hyperactivity of control mechanisms operative in utero and which normally protect the fetoplacental unit against the toxic effect of Th-1 cytokines.