Delivery mode and the incidence of atopic sensitization and food allergy in a Finnish child population.

BACKGROUND: Caesarean section (CS) has been associated with an increased risk of subsequent atopic diseases, particularly asthma and respiratory allergies, but controversial findings have also been reported. Our aim was to clarify the association between the delivery mode and longitudinal (atopic) outcomes. METHODS: The target population was identified from the population register and comprised all children born between 2001 and 2006 and living in the province of South Karelia, Finland (N = 5564). The information on the delivery mode was available for 5552 children from the Finnish Medical Birth Register. Results of allergy tests (skin prick tests, specific IgE and open food challenges, OFCs) were collected from patient records of all healthcare units in the area. RESULTS: By 12 years of age, the cumulative incidence of atopic sensitization was 15% for those born by normal vaginal delivery (VD), 20% (adjusted RR 1.28; 95% CI 0.99-1.65) by assisted VD, 20% (adjusted RR 1.28; 95% CI 1.02-1.61) by elective CS and 20% (adjusted RR 1.24; 95% CI 0.99-1.56) by others, for example emergency CS. Among the offspring of mothers without atopic diseases, the incidence of food allergy (positive OFC) was 6% for those born by elective CS and 2% for those born by normal VD (adjusted RR 2.41; 95% CI 1.19-4.88), while the respective incidences were 5% and 6% (adjusted RR 0.82; 95% CI 0.33-2.06) among the offspring of mothers with atopic diseases. CONCLUSION: By adolescence, the cumulative incidences of atopic sensitization was highest among those born by assisted VD or CS. The incidence of food allergy was highest among those born by elective CS among the offspring of mothers without atopic diseases.

Atopic diseases of the parents predict the offspring's atopic sensitization and food allergy.

BACKGROUND: In genetic studies and selected study populations, parental atopy has been associated with atopic diseases in offspring. Our aim was to identify the association between parental atopic diseases and the offspring's atopic sensitization and food allergies, and their effect modifications due to the offspring's sex. METHODS: The study population (N = 5564) (born between 2001 and 2006) was identified from the population register and live in the province of South Karelia, Finland. Questionnaire-based information on parental atopic diseases was available for 3592 children. The results of skin prick tests, specific IgE tests, and open food challenges (OFC) were collected from patient records. RESULTS: By 12 years of age, the cumulative incidence of sensitization to food (14% vs 7%, hazard ratio 2.13; 95% CI 1.68-2.69), animal (10% vs 6%, 1.86; 1.42-2.44), and pollen allergens (12% vs 6%, 2.43; 1.85-3.19), as well as food allergies (positive OFC, 5% vs 2%, 2.28; 1.57-3.33), was higher in the offspring of parents with atopic diseases. The cumulative incidence for pollen sensitization was twofold higher for the female offspring of parents with atopic diseases than those of parents without, while it was almost threefold higher among males. The association between parental pollen allergy and the offspring's pollen sensitization was modified by sex according to additive scale estimates (RERI 1.03; 95% CI 0.13-1.91). CONCLUSION: Until adolescence, parental atopic diseases have a relatively strong association with the offspring's, particularly male offspring's, atopic sensitization, and food allergies. A pronounced association was found between parental pollen allergy and the male offspring's pollen sensitization.

Occurrence of pollen season at the end of the first trimester predicts clinical atopic diseases in the offspring: A Finnish population-based study.

OBJECTIVE: To evaluate the association between potential exposure to different pollen concentrations at the 11th fetal week and subsequent clinical atopic diseases. STUDY DESIGN AND SETTING: Parents of 1- to 4-year-old children (N = 3035) returned a questionnaire regarding physician-diagnosed atopic diseases. The children were born between 2001 and 2005 in the province of South Karelia, Finland. Results of allergy tests were collected from patient records in the area. RESULTS: The prevalence of atopic diseases with sensitisation was higher in children whose 11th fetal week occurred during pollen rather than non-pollen season: atopic eczema 6.3% vs. 4.3% (adjusted odds ratio, aOR 1.58, 95% CI 1.10─2.28), food allergy 5.7% vs. 3.9% (1.63; 1.12─2.38), respiratory allergy or asthma 3.7% vs. 2.2% (2.03; 1.24─3.33) and any atopic diseases 7.4% vs. 5.5% (1.48; 1.07─2.05), respectively. Respectively, the prevalence was higher in the children exposed to high rather than low tree pollen concentrations (>1000 vs. <10 particles/m3) at the 11th fetal week: 12.1% vs. 4.4% (3.35; 1.89─5.95), 12.1% vs. 3.9% (3.77; 2.11─6.72), 4.7% vs. 2.5% (2.95; 1.21─7.20) and 14.0% vs. 5.7% (3.15; 1.86─5.35). CONCLUSION: Coincidence of potential exposure to high tree pollen concentrations at the 11th fetal week is associated with subsequent clinical atopic diseases with sensitisation.

Diverse age-incidence patterns of atopic sensitization in an unselected Finnish population up to 12 years.

BACKGROUND: The temporal sequence in which allergic sensitization to different allergens emerges is not well characterized at the level of general population. OBJECTIVE: We describe the incidence patterns of atopic sensitization to different allergens from birth up to 12 years of age in an unselected Finnish population. METHODS: The study population comprised all children born between 2001 and 2006 identified from the nationwide population register as residents of the province of South Karelia, Finland (n = 5564). The results of allergy tests (22,380 results from skin prick tests, immunoglobulin E [IgE] antibodies, and open food challenges [OFCs], performed in 1827 children) were collected from patient records of all the health care units in the area. RESULTS: The incidence rates of positive results for food and animal allergens as well as positive OFCs for cow's milk showed prominent peaks at 5 months of age. Positive results for pollen allergens started to emerge after 1.5 years of age. The 12-year cumulative incidence of sensitization to food, animal, pollen, and any allergens was 12%, 8%, 10%, and 18%, respectively. The cumulative incidence of sensitization to house dust mites was 1% and to molds or latex less than 1%. Firstborn boys had the highest, and those who were not firstborn girls and children born in rural municipalities had the lowest early incidence of sensitization to inhalation allergens. CONCLUSION: In the unselected population, the atopic sensitization against food and animal allergens began before 6 months of age and was followed by sensitization to pollen allergens before 2 years of age. Primary prevention of sensitization to food and inhalation allergens should therefore occur in early infancy.

Dog and cat exposure and respective pet allergy in early childhood.

BACKGROUND: The association of dog and cat exposure in early childhood with the incidence of respective allergies has remained controversial. The aim of the study was to obtain population-based evidence on the association of early exposure to dog or cat, or both, with dog and cat allergies. METHODS: The study population was identified from the nationwide population register comprising all children aged 1-4 yr (N = 4779) born between 2001 and 2005 and living in the province of South Karelia, Finland. Cross-sectional questionnaire data on pet exposure in infancy and physician-diagnosed pet allergies were obtained from 3024 participants and merged with longitudinally accumulated data on sIgE and skin prick tests indicating allergic sensitization abstracted from all patient records in the area. RESULTS: The adjusted relative incidence of positive test results (with 95% confidence intervals) was 2.69 (1.45-5.02) for dog and 5.03 (2.47-10.2) for cat allergens among children exposed to a respective pet alone compared with children without such exposure. The corresponding adjusted prevalence odds ratios for diagnosed dog and cat allergies were 1.75 (0.77-3.79) and 5.13 (2.30-11.4), respectively. The association between pet exposure and the incidence of positive test results was independent of parents' allergies. CONCLUSIONS: Early exposure to dog and cat at home is associated with a higher incidence of respective pet allergy during the first four years of life. Further evidence from population-based studies with longer follow-up is required to justify any recommendation concerning early pet contacts with a view to preventing pet allergies later in life.

Season of the first trimester of pregnancy predicts sensitisation to food allergens in childhood: a population-based cohort study from Finland.

OBJECTIVE: To examine whether the season of birth or season of the early phase of gestation is associated with sensitisation to food allergens in children, with special reference to mothers' pollen exposure in spring. DESIGN: A population-based cohort study linking information from a questionnaire survey to allergy tests performed on the target population and regional pollen counts. POPULATION: Children born in 2001-6 who were resident in the province of South Karelia, Finland, at the time of the survey (N=5920). MAIN OUTCOME MEASURES: A positive result in any food allergy test or food-specific immunoglobulin E test (sIgE). RESULTS: The cumulative incidence of a positive food allergy test up to the age of 4 years was highest among children born in October-November (10%) and lowest among those born in June-July (5%), and correspondingly highest among children who were in their 11th gestational week in April-May (11%), the season of high concentrations of birch and alder pollen, and lowest among those reaching that stage in December-January (6%). The amplitude of seasonal variation in any test, estimated as the relative ratio between the peak and trough of the smoothed incidence curve over the year, was 2.03 (95% CI 1.52 to 2.76). The amplitudes of positive sIgE were especially pronounced for milk (3.07; 95% CI 1.81 to 5.50) and egg (3.03; 95% CI 1.86 to 5.18). CONCLUSIONS: Children having their early gestational period in the pollen season for broad-leafed trees are more prone to sensitisation to food allergens than other children.

Real-life epidemiology of food allergy testing in Finnish children.

BACKGROUND: The cumulative incidence of parental-reported symptoms of food allergy (FA) during the first years of life is estimated to exceed 30%. However, the occurrence and determinants of FA testing in a general child population have remained unknown. METHODS: The study population comprised all 5920 children aged 0-4 yr in the province of South Karelia, Finland, identified from the nationwide population register. The study included a questionnaire survey and a retrospective collection of FA test results (skin prick tests, IgE antibodies, or open food challenges) from the patient records of the entire study population. The questionnaire and patient record data were linked together on an individual basis with the parents' permission. RESULTS: A total of 5849 FA tests had been performed on 961 children. By the age of 4 yr, the cumulative incidence of FA testing was 18% for any food item; 17% for essential items (milk, egg, cereals) and 9% for other food items. Essential food items had been tested in 90% of children who reportedly had a physician-diagnosed FA for these. The incidence of testing was 30% higher in boys than in girls and twofold higher among the offspring whose either or both parents reportedly had some allergic manifestation. CONCLUSIONS: A large proportion of children are subjected to FA testing in their early years. This result shows the need to evaluate the financial burden of FA testing and to improve current testing practices.

SKARP--A population-based cohort study of childhood food-associated symptoms perceived by parents and food allergies diagnosed by physicians: design, methods and participation.

BACKGROUND: Few epidemiological studies exist on food-associated symptoms and allergies in large unselected child populations. AIMS: To describe the design, methods and participation rate of the South Karelian Allergy Research Project (SKARP), a population-based epidemiological study on food-associated symptoms and physician-diagnosed food allergies. METHODS: The study population of 5,973 children born between 2001 and 2006 and resident in the province of South Karelia, Finland, was identified from the nationwide population register. The parents received a questionnaire to be returned at their child's annual visit to the child health clinic, where supplementary interviews were performed. Results of allergy tests (skin prick tests, immunoglobulin E antibodies and open food challenges) performed on participants and non-participants were collected from the relevant health care units in the area. RESULTS: Participation rates in the questionnaire study were 54% (644/1,194) among the parents of neonates and 69% (3308/4,779) among those of the children aged 1 to 4 years. Cooperation with the child health clinics and mailing of a reminder questionnaire improved participation by 8 and 10 percentage points, respectively. The final participation rate seemed to be unaffected by whether the child had or had not been tested for suspected allergy. CONCLUSIONS: A reasonably good participation rate and almost complete coverage of allergy tests were achieved thanks to successful cooperation with the child health clinics and test laboratories. This baseline study forms a representative database to estimate the occurrence of food-associated symptoms, physician-diagnosed food allergies and allergy testing in the general population.

Heredity of food allergies in an unselected child population: an epidemiological survey from Finland.

The heredity of food allergies (FA) has not previously been addressed in a large unselected child population. Our target population comprised all children born from April 2001 to March 2006 resident in one province of South-East Finland (n c. 6000), as identified from the national population register. In a questionnaire survey conducted in 2005-2006, data were obtained on allergic manifestations (FA symptoms, atopic rash, allergic asthma, hay fever/pollen allergy, or animal allergy) in the biologic parents of 3800 children (64% of the total). Concurrently with the survey but independently of it, results of specific immunoglobulin E antibodies (sIgE), skin prick tests (SPT), and open food challenges (OFC) in the offspring were collected from patient records throughout the province. Up to the age of 4 yr, the incidences of any positive FA test, a positive SPT or sIgE for food items, and a positive OFC in these children were threefold higher if both parents reported having an allergic manifestation and twofold higher if either mother or father had such a manifestation when compared with children whose parents did not report any of these conditions. The estimated risk of any positive FA test increased by a factor of 1.3 (95% CI 1.2-1.4) for each additional allergic manifestation in the parents. Positive FA tests in the offspring were relatively strongly associated with the reports of allergic phenotypes and the number of these phenotypes in their biologic parents.

Occurrence of parent-reported food hypersensitivities and food allergies among children aged 1-4 yr.

Food allergies (FAs) and hypersensitivities (FHSs) have rarely been studied in large unselected child populations. This population-based cross-sectional survey estimated the occurrence of FHS as perceived by parents and that of FA diagnosed by a physician among children aged 1-4 yr in south-eastern Finland. Before the scheduled annual follow-up visit to the local child health clinic, the parents of children who were born between 1 April, 2001 and 31 March, 2005, and living in the Province of South Karelia (data from Finnish Population Register) were mailed a questionnaire containing items on the child's background, physician-diagnosed FAs and FHSs perceived by the parents. The questionnaires were returned during the visit. Three thousand three hundred and eight (69%) out of the 4779 questionnaires were returned. The lifetime prevalence of physician-diagnosed FAs was 9%. In an additional 21%, FHSs were perceived by the parents only. In a further 19% at least one food item had been eliminated from the diet without any perception of symptoms, this proportion having a downward trend by age. Physician-diagnosed FAs were more common in boys than in girls. Cow's milk was the most commonly reported cause of food-associated symptoms (13% of all children). One-third of the children aged 1-4 yr suffered from food-associated symptoms, and in an additional fifth at least one food item had been eliminated from their diet, implying that every other child had possibly been subjected to some form of elimination diet.