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Biomedical subjects

Mads Melbye

Publications and source records attributed to Mads Melbye.

At least 37 records · Page 2Linked to original sources
PubMed2005

Sibship characteristics and risk of allergic rhinitis and asthma.

Studying associations between sibship characteristics and allergic diseases in detail may contribute clues to their etiology. The authors studied associations between sibship characteristics and risk of self-reported allergic rhinitis and asthma among 31,145 pregnant women participating in a nationwide study in Denmark during 1997-2000. Increasing sibship size was associated with a decreased risk of allergic rhinitis and asthma with allergic rhinitis but not with asthma without allergic rhinitis. The protective effect of having older siblings was stronger than the protective effect of having younger siblings for both allergic rhinitis and asthma with allergic rhinitis. There was no association between interval to closest older or younger sibling and risk of allergic rhinitis or asthma with allergic rhinitis, while the risk of asthma without allergic rhinitis increased with intervals of 2 or more years compared with less than 2 years to the nearest older sibling. The protective effect of having siblings on the risk of asthma with allergic rhinitis could be explained by a protective effect of siblings on the risk of allergic rhinitis alone. In conclusion, our findings suggest that different etiologic mechanisms are involved for allergic rhinitis and asthma with respect to the effect of sibship characteristics. Furthermore, the findings that allergic rhinitis was associated with the number of younger siblings but not with the age interval to younger siblings support the hypothesis of an influence of postnatal mechanisms and suggest that these mechanisms may not necessarily be operating only in early life.

Adolescent↗
PubMed2005

Body mass index and risk of malignant lymphoma in Scandinavian men and women.

BACKGROUND: The incidence of non-Hodgkin lymphoma and prevalence of obesity are increasing globally. A suggested positive association between obesity and risk of non-Hodgkin lymphoma has prompted us to investigate the relationship between body mass index (BMI) and risk of malignant lymphoma subtypes in a population-based case-control study. METHODS: Telephone interviews were conducted with 3055 case patients with non-Hodgkin lymphoma and 618 case patients with Hodgkin lymphoma diagnosed between October 1, 1999, and August 30, 2002, and 3187 population-based control subjects. The interviews assessed current height, normal adult weight, and other possible risk factors. Multivariable odds ratios (ORs) and corresponding 95% confidence intervals (CIs) for risk of lymphoma were estimated by unconditional logistic regression. All statistical tests were two-sided. RESULTS: BMI was not associated with risk of overall non-Hodgkin lymphoma or of Hodgkin lymphoma (for example, comparing the highly obese group [BMI > or =35.0 kg/m2] with the normal-weight group [BMI = 18.5-24.9 kg/m2], OR for risk of non-Hodgkin lymphoma = 0.9, 95% CI = 0.6 to 1.3; P(trend) across all categories of BMI = .27). BMI was also not associated with risk of any non-Hodgkin lymphoma subtype evaluated, although there was some evidence of a positive association with risk of diffuse large B-cell lymphoma (for example, comparing the highly obese group with the normal-weight group, OR for diffuse large B-cell lymphoma = 1.5, 95% CI = 0.9 to 2.4; P(trend) =.05). CONCLUSIONS: Excess weight does not appear to be associated with an increased risk of malignant lymphoma in general, or with a risk of most major lymphoma subtypes. Hence, the growing incidence of obesity is unlikely to be an important contributor to the increasing incidence of non-Hodgkin lymphoma worldwide.

Adult↗
PubMed2005

Ultraviolet radiation exposure and risk of malignant lymphomas.

BACKGROUND: The incidence of malignant lymphomas has been increasing rapidly, but the causes of these malignancies remain poorly understood. One hypothesis holds that exposure to ultraviolet (UV) radiation increases lymphoma risk. We tested this hypothesis in a population-based case-control study in Denmark and Sweden. METHODS: A total of 3740 patients diagnosed between October 1, 1999, and August 30, 2002, with incident malignant lymphomas, including non-Hodgkin lymphoma, chronic lymphocytic leukemia, and Hodgkin lymphoma, and 3187 population controls provided detailed information on history of UV exposure and skin cancer and information on other possible risk factors for lymphomas. Odds ratios (ORs) with 95% confidence intervals (CIs) were calculated by logistic regression. Statistical tests were two-sided. RESULTS: Multivariable-adjusted analyses revealed consistent, statistically significant negative associations between various measures of UV light exposure and risk of non-Hodgkin lymphoma. A high frequency of sun bathing and sunburns at age 20 years and 5-10 years before the interview and sun vacations abroad were associated with 30%-40% reduced risks of non-Hodgkin lymphoma (e.g., for sunbathing four times a week or more at age 20 versus never sunbathing, OR = 0.7, 95% CI = 0.6 to 0.9; for two or more sunburns a year at age 20 versus no sunburns, OR = 0.6, 95% CI = 0.5 to 0.8). These inverse associations increased in strength with increasing levels of exposure (all P(trend)< or =.01). Similar, albeit weaker, associations were observed for Hodgkin lymphoma. There were no clear differences among non-Hodgkin lymphoma subtypes, although associations were stronger for B-cell than for T-cell lymphomas. A history of skin cancer was associated with a doubling in risks of both non-Hodgkin and Hodgkin lymphoma. CONCLUSIONS: A history of high UV exposure was associated with reduced risk of non-Hodgkin lymphoma. The positive association between skin cancer and malignant lymphomas is, therefore, unlikely to be mediated by UV exposure.

Adult↗
PubMed2005

Lung function in Greenlandic and Danish children and adolescents.

Respiratory morbidity in Inuit children is high. However, little is know regarding lung function measures in this population. The forced expiratory volumes in one second (FEV(1)) and forced vital capacity (FVC) in 888 Greenlandic Inuits (N=888) and Danes (N=477) aged 6-18 years were compared. Furthermore, associations between level of lung function and atopy and lifestyle factors were estimated in Greenlanders. The effect of height on FEV(1) and FVC was significantly different in Greenlanders and Danes, this difference in lung function increased with increasing height, and could not be explained by differences in age weight and BMI. Thus, Greenlanders taller than 130 cm had up to 300-400 ml higher FEV(1) and FVC compared with Danes of the same height. Among Greenlanders, those living in settlements had the highest levels of both FEV(1) and FVC. Greenlanders had elevated levels of FEV(1) and FVC compared with Danes. The Inuit having a shorter limb length in relation to trunk height may account for these differences. However, our finding that Greenlanders living in settlements had the highest lung function level also suggests a possible role of factors in the traditional Greenlandic lifestyle.

Adolescent↗
PubMed2005

Seroprevalence and risk factors for Helicobacter pylori infection in Greenlanders.

BACKGROUND: In contrast to most populations worldwide, the incidence of gastric cancer increases among Inuit in Greenland. Contributing factors to this increase are unknown, but Helicobacter pylori may be involved. However, little is known regarding the epidemiology of H. pylori in Arctic communities. With the aim of determining age-specific prevalence, risk factors, and association with clinical conditions of H. pylori infection, we carried out a population-based study of H. pylori in Sisimiut, the second biggest town of Greenland. MATERIALS AND METHODS: A population-based sample of 685 persons had serum drawn that was analyzed for H. pylori IgG antibodies using enzyme-linked immunosorbent assay (ELISA). Risk factors analyses were carried out using multivariate logistic regression models. RESULTS: The seroprevalence was lowest among children aged 0-4 years (6%), but increased rapidly thereafter. In persons aged 15-87 years the seroprevalence had stabilized around 58%. Total number of children in household, number of older, but not younger, siblings and narrow age gap to closest older sibling were associated with H. pylori seropositivity. In contrast, number of adults in household and socioeconomic status did not influence serostatus. CONCLUSIONS: The age-specific prevalence pattern in Greenland is intermediate between that of developing and developed countries. The risk factor pattern indicates crowding and older siblings in particular to be key elements in risk of infection.

Adolescent↗
PubMed2005

Dietary factors and risk of non-hodgkin lymphoma in men and women.

BACKGROUND: The incidence of non-Hodgkin lymphoma (NHL) has increased worldwide in recent decades. Diet could influence NHL risk by modulating the immune system, although evidence is limited. We did a population-based case-control study to determine whether differences in diet were associated with NHL risk. METHODS: A total of 597 NHL cases and 467 population controls in Sweden completed a semiquantitative food frequency questionnaire evaluating their dietary habits 2 years before the interview. Unconditional logistic regression was used to estimate the odds ratios (OR) and corresponding 95% confidence intervals (95% CI) for associations between food intake and risk of NHL. RESULTS: High consumption of dairy products and fried red meat was associated with increased risk of NHL. The OR of NHL for individuals in the highest quartile compared with the lowest quartile of dairy intake was 1.5 (95% CI, 1.1-2.2; P(trend) = 0.003). The OR for the highest versus lowest quartile of fried red meat intake was 1.5 (95% CI, 1.0-2.1; P(trend) = 0.02). In contrast, high consumption of fruits and vegetables was associated with reduced risk of NHL, particularly follicular lymphoma, among women but not men. Compared with the lowest quartile of vegetable intake, the OR of follicular lymphoma among women in the highest quartile of vegetable intake was 0.3 (95% CI, 0.1-0.7; P(trend) = 0.002). CONCLUSIONS: The positive associations of NHL risk with dairy products and fried red meat and the inverse association with fruits and vegetables suggest that diet affects NHL risk and could explain the increase of some histopathogic subtypes.

Case-Control Studies↗
PubMed2005

Cigarette smoking and risk of non-Hodgkin's lymphoma--a population-based case-control study.

BACKGROUND: Epidemiologic evidence of an association between tobacco smoking and non-Hodgkin's lymphoma has been conflicting. This may reflect that non-Hodgkin's lymphoma comprises several distinct disease entities with different etiologies, as some studies have indicated an association between smoking and follicular lymphoma. OBJECTIVE: To investigate the association between cigarette smoking and non-Hodgkin's lymphoma risk, overall and by subtype. METHODS: As part of a nationwide Danish-Swedish population-based case-control study, we interviewed 3,055 incident non-Hodgkin's lymphoma patients and 3,187 population controls. All lymphomas were uniformly classified according to the WHO classification. We used unconditional logistic regression to estimate adjusted odds ratios (OR) and 95% confidence intervals (95% CI) for the association between cigarette smoking and risk of non-Hodgkin's lymphoma. RESULTS: Cigarette smoking was not associated with the risk of non-Hodgkin's lymphoma overall (OR, 0.97; 95% CI, 0.87-1.08) nor with the major subgroups such as diffuse large B-cell lymphoma (OR, 0.94; 95% CI, 0.79-1.10), chronic lymphocytic leukemia (OR, 0.86; 95% CI, 0.72-1.02), or follicular lymphoma (OR, 1.03; 95% CI, 0.85-1.24). Female smokers were at a marginally increased risk of follicular lymphoma (OR, 1.41; 95% CI, 1.04-1.92). Men who had ever smoked had a significantly increased risk of T-cell lymphoma (OR, 1.67; 95% CI, 1.11-2.51). No dose-response association with cigarette smoking could be established for any lymphoma subgroup. CONCLUSION: We found little evidence of an association between cigarette smoking and non-Hodgkin's lymphoma risk overall. Although increased risks of follicular lymphoma in female smokers and of T-cell lymphoma in male smokers were suggested, no dose-response relationship was observed, leaving limited support for causality.

Adolescent↗
PubMed2005

Risk factors for idiopathic congenital/infantile cataract.

PURPOSE: To investigate maternal, demographic, and pre- and perinatal risk factors for idiopathic congenital/infantile (ICI) cataract. METHODS: Based on national registries, a cohort of all children born in Denmark and aged 0 to 17 years during 1977 to 2001 was established, and congenital/infantile cataract cases were identified. Cases of unknown/idiopathic cause were included in the study. Associations between maternal, demographic, and pre- and perinatal factors with the development of cataract were investigated. RESULTS: In a cohort of 2.9 million children, 1027 cases of congenital/infantile cataract were identified. Of the children in those cases, 629 were born in Denmark and had ICI. Bilateral isolated cataract cases were male dominated (62%; 95% confidence interval [CI], 56%-69%) but not unilateral isolated cases (40%; 95% CI, 34%-47%). Older age (> or =40 years) of mothers at delivery and caesarean section increased the risk of ICI cataract. Low birth weight (< 2000 g) was associated with a 10.6-fold (95% CI, 6.99-16.10) increased risk of bilateral, but not unilateral, ICI cataract. No significant associations were found with birth order, month/place of birth, or cigarette smoking during pregnancy. CONCLUSIONS: Variables indicative of environmental influence were not associated with ICI cataract. Low-birth-weight children (< 2000 g) had a significantly increased risk of bilateral ICI, whereas no strong risk factors were found for unilateral cataract. Together with the sex difference, this suggests that the etiologies of bilateral and unilateral cataract are different.

Adolescent↗
PubMed2004

Birth weight and risk for childhood leukemia in Denmark, Sweden, Norway, and Iceland.

BACKGROUND: Compelling evidence suggests that childhood leukemia often originates in utero. Birth weight is one of the few pregnancy-related risk factors that has been associated with leukemia risk, but the association has remained poorly characterized. We conducted a population-based case-control study in Denmark, Sweden, Norway, and Iceland to investigate the association between birth weight (and other birth characteristics) and the risk of childhood leukemia. METHODS: Overall, 1905 children (aged 0-14 years) with acute lymphoblastic leukemia (ALL) and 299 children with acute myeloid leukemia (AML) diagnosed between January 1, 1984, and December 31, 1999, were identified in the Nordic Society of Paediatric Haematology and Oncology acute leukemia database. Each case patient was matched to five population control subjects (n = 10745) on nationality, age, and sex. All live-born siblings of case patients (n = 3812) and control subjects (n = 17,937) were also identified in population registers. Information on birth weight and gestational age at birth was ascertained from the national Medical Birth Registers. The association between various birth characteristics and leukemia risk was assessed by conditional logistic regression. All statistical tests were two-sided. RESULTS: Risk of ALL overall was statistically significantly associated with birth weight (odds ratio [OR] = 1.26 per 1-kg increase in birth weight, 95% confidence interval [CI] = 1.13 to 1.41). The association was similar for B- and T-lineage ALL and across all diagnostic ages (0-14 years). However, children with ALL did not weigh more at birth than their siblings. Statistically significantly reduced risks of B-precursor ALL were observed with increasing position in the birth order (OR = 0.90 per position increase, 95% CI = 0.84 to 0.96) and increasing gestational age (OR = 0.87 per 2-week increase in gestational age, 95% CI = 0.81 to 0.94). Risk of AML did not vary monotonically with birth weight, and low birth weight (<1500 g [i.e., 3.3 pounds]) was associated with the highest risk. CONCLUSION: Our results are compatible with the hypothesis that a high birth weight is associated with an increased risk of ALL.

Adolescent↗
PubMed2004

Growth patterns and the risk of breast cancer in women.

BACKGROUND: Adult height and body-mass index influence the risk of breast cancer in women. Whether these associations reflect growth patterns of the fetus or growth during childhood and adolescence is unknown. METHODS: We investigated the association between growth during childhood and the risk of breast cancer in a cohort of 117,415 Danish women. Birth weight, age at menarche, and annual measurements of height and weight were obtained from school health records. We used the data to model individual growth curves. Information on vital status, age at first childbirth, parity, and diagnosis of breast cancer was obtained through linkages to national registries. RESULTS: During 3,333,359 person-years of follow-up, 3340 cases of breast cancer were diagnosed. High birth weight, high stature at 14 years of age, low body-mass index (BMI) at 14 years of age, and peak growth at an early age were independent risk factors for breast cancer. Height at 8 years of age and the increase in height during puberty (8 to 14 years of age) were also associated with breast cancer. The attributable risks of birth weight, height at 14 years of age, BMI at 14 years of age, and age at peak growth were 7 percent, 15 percent, 15 percent, and 9 percent, respectively. No effect of adjusting for age at menarche, age at first childbirth, and parity was observed. CONCLUSIONS: Birth weight and growth during childhood and adolescence influence the risk of breast cancer.

Adolescent↗
PubMed2004

Childhood infections and risk of multiple sclerosis.

Multiple sclerosis has been hypothesized to be the result from an aberrant immune response possibly triggered by delayed exposure to a common childhood infection. Because the vast majority of previous studies testing this hypothesis have been based on a history of childhood infections recalled years to decades later in adulthood, we investigated whether age at six common childhood infections was associated with risk of multiple sclerosis, using information recalled in the childhood of a historical cohort of school children in Denmark. Cases included all individuals with multiple sclerosis in the country born between 1940 and 1975, who had attended school in the capital, Copenhagen. Controls were age- and sex-matched peers. School health records were obtained for all subjects. The records contained information on measles, pertussis, scarlet fever, birth order, sibship size, social class of the father, school years, and name of school and attended school classes for children born since 1940 (n(cases) = 455, n(controls) = 1801). For children born since 1950, the records also contained information on rubella, varicella and mumps (n(cases) = 182, n(controls) = 690). Neither age at infection with measles, rubella, varicella, mumps, pertussis and scarlet fever (upper age limit, 14 years) nor the cumulative number of these infections between the ages of 10 and 14 years was associated with the risk of multiple sclerosis. In addition, the risk of multiple sclerosis was not associated with birth order or social class. No clustering of multiple sclerosis in school classes was observed. Our findings suggest that measles, rubella, mumps, varicella, pertussis and scarlet fever, even if acquired late in childhood, are not associated with increased risk of multiple sclerosis later in life.

Adolescent↗
PubMed2004

Impact of routine vaccination with a pertussis toxoid vaccine in Denmark.

In many countries, acellular pertussis vaccines have replaced whole-cell vaccines. We evaluated the impact of a pertussis toxoid vaccine on pertussis in Denmark. We calculated incidence rates for pertussis before and after pertussis toxoid vaccine was introduced, and estimated vaccination effectiveness (VE). We found that routine vaccination with pertussis toxoid vaccine was effective against both hospitalisation with pertussis (VE, 93% for three doses) and non-hospitalised pertussis (VE, 78% for three doses). However, after the introduction we found an increase in pertussis among the youngest infants, a direct result of the new schedule (ages 3, 5 and 12 months) where the youngest infants are unvaccinated for a longer time-period compared with the prior schedule (ages 5, 9 weeks and 10 months).

Age Factors↗
PubMed2004

Breastfeeding and risk of atopic dermatitis, by parental history of allergy, during the first 18 months of life.

The role of breastfeeding in allergic diseases remains controversial. The authors studied the association between breastfeeding and development of atopic dermatitis during the first 18 months of life among children with and without a parental history of allergy. A cohort study of 15,430 mother-child pairs enrolled in The Danish National Birth Cohort was carried out between 1998 and 2000. Data on breastfeeding, atopic dermatitis, and potential confounders was obtained from telephone interviews conducted during pregnancy and when the children were 6 and 18 months of age. The cumulative incidence of atopic dermatitis was 11.5% at 18 months of age. Overall, current breastfeeding was not associated with atopic dermatitis (incidence rate ratio (IRR) = 0.91, 95% confidence interval (CI): 0.80, 1.04). Exclusive breastfeeding for at least 4 months was associated with an increased risk of atopic dermatitis in children with no parents with allergies (IRR = 1.29, 95% CI: 1.06, 1.55) but not for children with one (IRR = 1.11, 95% CI: 0.94, 1.31) or two (IRR = 0.88, 95% CI: 0.69, 1.13) parents with allergies (test for homogeneity, p = 0.03). The authors found no overall effects of exclusive or partial breastfeeding on the risk of atopic dermatitis. However, the effect of exclusive breastfeeding for 4 months or more depended on parental history of allergic diseases.

Asthma↗
PubMed2004

MMR vaccination and febrile seizures: evaluation of susceptible subgroups and long-term prognosis.

CONTEXT: The rate of febrile seizures increases following measles, mumps, and rubella (MMR) vaccination but it is unknown whether the rate varies according to personal or family history of seizures, perinatal factors, or socioeconomic status. Furthermore, little is known about the long-term outcome of febrile seizures following vaccination. OBJECTIVES: To estimate incidence rate ratios (RRs) and risk differences of febrile seizures following MMR vaccination within subgroups of children and to evaluate the clinical outcome of febrile seizures following vaccination. DESIGN, SETTING, AND PARTICIPANTS: A population-based cohort study of all children born in Denmark between January 1, 1991, and December 31, 1998, who were alive at 3 months; 537,171 children were followed up until December 31, 1999, by using data from the Danish Civil Registration System and 4 other national registries. MAIN OUTCOME MEASURES: Incidence of first febrile seizure, recurrent febrile seizures, and subsequent epilepsy. RESULTS: A total of 439,251 children (82%) received MMR vaccination and 17,986 children developed febrile seizures at least once; 973 of these febrile seizures occurred within 2 weeks of MMR vaccination. The RR of febrile seizures increased during the 2 weeks following MMR vaccination (2.75; 95% confidence interval [CI], 2.55-2.97), and thereafter was close to the observed RR for nonvaccinated children. The RR did not vary significantly in the subgroups of children that had been defined by their family history of seizures, perinatal factors, or socioeconomic status. At 15 to 17 months, the risk difference of febrile seizures within 2 weeks following MMR vaccination was 1.56 per 1000 children overall (95% CI, 1.44-1.68), 3.97 per 1000 (95% CI, 2.90-5.40) for siblings of children with a history of febrile seizures, and 19.47 per 1000 (95% CI, 16.05-23.55) for children with a personal history of febrile seizures. Children with febrile seizures following MMR vaccinations had a slightly increased rate of recurrent febrile seizures (RR, 1.19; 95% CI, 1.01-1.41) but no increased rate of epilepsy (RR, 0.70; 95% CI, 0.33-1.50) compared with children who were nonvaccinated at the time of their first febrile seizure. CONCLUSIONS: MMR vaccination was associated with a transient increased rate of febrile seizures but the risk difference was small even in high-risk children. The long-term rate of epilepsy was not increased in children who had febrile seizures following vaccination compared with children who had febrile seizures of a different etiology.

Child, Preschool↗
PubMed2004

Familial clustering of Hodgkin lymphoma and multiple sclerosis.

BACKGROUND: Epidemiologic similarities between Hodgkin lymphoma in young adults (i.e., between 15 and 44 years old) and multiple sclerosis have led to the suggestion that these diseases may have related etiologies. Previous investigations have not supported this hypothesis, but the negative results could have been caused by methodologic problems. We therefore assessed the risk of developing Hodgkin lymphoma for patients with multiple sclerosis and for their families and the risk of developing multiple sclerosis for patients with Hodgkin lymphoma and for their families. METHODS: We identified 11,790 patients with multiple sclerosis and 19,599 of their first-degree relatives in Danish population-based registers and followed them for the occurrence of Hodgkin lymphoma. Analogously, we identified 4381 patients with Hodgkin lymphoma and 7388 of their first-degree relatives and followed them for the occurrence of multiple sclerosis. The relative risks (RRs) of Hodgkin lymphoma and multiple sclerosis were expressed as standardized incidence ratios (i.e., the ratio between observed and expected numbers of outcomes based on age, sex, and period-specific incidence rates). All statistical tests were two-sided. RESULTS: Overall, six cases of Hodgkin lymphoma were identified in patients with multiple sclerosis (RR for Hodgkin lymphoma = 1.40, 95% confidence interval [CI] = 0.63 to 3.12), two of which occurred in young adults (RR = 1.59, 95% CI = 0.40 to 6.37). The risk of young-adult-onset Hodgkin lymphoma was statistically significantly increased in the first-degree relatives of patients with multiple sclerosis (RR = 1.93, 95% CI = 1.01 to 3.71; n = 9 such lymphomas). Two cases of multiple sclerosis were identified among young adult patients with Hodgkin lymphoma (RR for multiple sclerosis = 0.82, 95% CI = 0.20 to 3.27), and the risk for multiple sclerosis was statistically significantly increased in their first-degree relatives (RR = 2.76, 95% CI = 1.44 to 5.31; n = 9 such multiple sclerosis cases). CONCLUSION: The observed familial clustering of multiple sclerosis and young-adult-onset Hodgkin lymphoma is consistent with the hypothesis that the two conditions share environmental and/or constitutional etiologies.

Adolescent↗
PubMed2004

Cohort study of sibling effect, infectious diseases, and risk of atopic dermatitis during first 18 months of life.

OBJECTIVES: To determine whether early infectious diseases could explain the association between number of siblings and other markers of microbial exposure and the development of atopic dermatitis before the age of 18 months. DESIGN: Cohort study. Information on atopic dermatitis, infectious diseases occurring before 6 months of age, number of siblings, early day care, pet keeping, farm residence, and background factors was collected in telephone interviews. SETTING: Danish national birth cohort. PARTICIPANTS: 24,341 mother-child pairs. MAIN OUTCOME MEASURES: Incidence rate ratios of atopic dermatitis. RESULTS: 13,070 children (54%) had at least one clinically apparent infectious disease before 6 months of age. At age 18 months, 2638 (10.8%) of the children had had atopic dermatitis. The risk of atopic dermatitis increased with each infectious disease before 6 months of age (incidence rate ratio 1.08, 95% confidence interval 1.04 to 1.13). The risk of atopic dermatitis decreased with each additional exposure to three or more siblings, day care, pet ownership, and farm residence (0.86, 0.81 to 0.93). CONCLUSIONS: Early infections do not seem to protect against allergic diseases. The protective effect of number of siblings, day care, pet ownership, and farm residence remained after adjustment for clinically apparent infectious diseases, suggesting that the effect is established independently early in life.

Age Distribution↗