Supplementary appendix

Transcription

1 Supplementary appendix This appendix formed part of the original submission and has been peer reviewed. We post it as supplied by the authors. Supplement to: Pinart M, Benet M, Annesi-Maesano I, et al. Comorbidity of eczema, rhinitis, and asthma in IgE-sensitised and non-ige-sensitised children in MeDALL: a population-based cohort study. Lancet Respir Med 2014; published online Jan 14.

2 Comorbidity of eczema, rhinitis, and asthma in IgE sensitised and non IgE sensitised children in MeDALL: a population based cohort study Mariona Pinart, Marta Benet, Isabella Annesi Maesano, Andrea von Berg, Dietrich Berdel, Karin C L Carlsen, Kai Håkon Carlsen, Carsten Bindslev Jensen, Esben Eller, Maria Pia Fantini, Jacopo Lenzi, Ulrike Gehring, Joachim Heinrich, Cynthia Hohmann, Jocelyne Just, Thomas Keil, Marjan Kerkhof, Manolis Kogevinas, Sibylle Kolezko, Gerard H Koppelman, Inger Kull, Susanne Lau, Erik Melén, Isabelle Momas, Daniela Porta, Dirkje S Postma, Fanny Rancière, Henriette A Smit, Renato T Stein, Christina G Tischer, Maties Torrent, Magnus Wickman, Alet H Wijga, Jean Bousquet, Jordi Sunyer, Xavier Basagaña, Stefano Guerra, Judith Garcia Aymerich, Josep M Antó, In collaboration with the WHO Collaborative Centre on Asthma and Rhinitis (Montpellier) Supplemental Methods Disease definitions Information about eczema, rhinitis and asthma outcomes was obtained through questionnaires from each of the cohorts. We used definitions of these diseases that were agreed by a panel of experts, comprising participants of MeDALL and invited external participants, which aimed at re defining the current definitions of eczema, rhinitis, and asthma as well as their phenotypes from childhood to young adulthood using a modified version of the GA 2 LE questionnaire for current asthma definition and ISAAC questions to define current rhinitis and current eczema. To apply the MeDALL definitions, harmonising decisions were taken by a panel of co authors. Such definitions S1 and accompanying documents are also available upon request. Current asthma: MeDALL agreed to develop a modified version of the GA 2 LE questionnaire S2 used for the survey conducted in Asthma was defined as a positive answer to at least two of the three following questions: Doctordiagnosed asthma ever: Has your child ever been diagnosed by a doctor as having asthma? ; Asthma medication in the past 12 months: Has your child taken any medicines for asthma (including inhalers, nebulizers, tablets or liquid medicines) or breathing difficulties (chest tightness, shortness of breath) in the last 12 months? ; and Wheezing in the past 12 months according to ISAAC parental core questionnaire S3 AD/OR breathing difficulties (chest tightness and shortness of breath) in the past 12 months: Have you had wheezing or whistling in your chest at any time in the last 12 months? and/or Has your child had breathing difficulties (chest tightness, shortness of breath) in the past 12 months?. Current rhinitis: Rhinitis was defined as a positive answer to the following ISAAC questions S4,S5 : Has your child had problems with sneezing, or a runny, or blocked nose when s/he did not have a cold or flu? If yes In the past 12 months, has this nose problem been accompanied by itchy watery eyes?. Current eczema: Eczema was defined as a positive answer to the following three questions from ISAAC S3 : Has your child ever had an itchy rash which was coming and going for at least six months? ; Has your child had this itchy rash at any time in the last 12 months? and Has this itchy rash at any time affected any of the following places: the folds of the elbows, behind the knees, in front of the ankles, under the buttocks, or around the neck, ears or eyes?. Harmonisation process According to the MeDALL definitions of current asthma, current rhinitis and current eczema the following variables were used to create the definitions agreed during the expert meeting. Variables used to create the operational definition for asthma (i) Doctor diagnosis of asthma ever; (ii) Medications for asthma treatment during the last 12 months; and (iii) Wheezing in the past 12 months according to ISAAC parental core questionnaire The available information received previously from each of the participating birth cohorts allowed the direct use of variables (i) and (ii). Although we could not use directly the variable for wheezing in the past 12 months according to ISAAC parental core questionnaire, we were able to create the variable using the available information on wheezing attacks in the last 12 months. A child was coded as having asthma when s/he had two of the three symptoms and was considered missing when s/he had missing values in at least two of the requested variables; the rest of the children were coded as not having asthma. Variables used to create the operational definition for rhinitis (i) Has your child had problems with sneezing or a runny or blocked nose when s/he did not have a cold or flu? ; and (ii) If yes In the past 12 months, has this nose problem been accompanied by itchy watery eyes? The available information received previously from each of the participating cohorts allowed the direct use of the variables. A child was coded as having rhinitis if both of the questions were positive, otherwise was coded as no unless both of the variables were missing. 1

3 Variables used to create the operational definition for eczema (i) Has your child ever had an itchy rash which was coming and going for at least 6 months? ; (ii) Has your child had this itchy rash at any time in the last 12 months? ; and (iii) Has this itchy rash at any time affected any of the following places: the folds of the elbows, behind the knees, in front of the ankles, under the buttocks, or around the neck, ears or eyes? The available information received previously from each of the participating cohorts allowed the direct use of variables. A child was considered as having eczema if the three questions were positive, otherwise was considered as not having eczema. Sensitisation was defined as having specific IgE concentration 0 35 kua/l in serum against at least one of the following aero and food allergens: house dust_mite, cat dander, birch pollen, grass pollen, milk and egg. In order to have comparable information for these allergens in all birth cohorts, we harmonised house dust mite and grass pollen. For some cohorts (BAMSE, DARC, ECA, AMICS, GIIplus and PIAMA) information about IgE sensitisation to house dust mite was available as two separated variables regarding Dermatophagoides pteronyssinus (dpt) and Dermatophagoides farinae (dpf). To create a single categorical variable allowing for house dust mite, we did as follows: a child was considered sensitised to house dust mite if the child was positive (> 0 35) to at least one of the two allergens ( dpt or dpf ) and not sensitised to house dust mite if he or she was negative to both allergens. The same rule was applied for other cut offs of IgE sensitisation (0 70 and 3 5). When only one of the variables (dpt or dpf) was available, that variable was used as house dust mite. For grass pollen the harmonisation was done by combining the following tested allergens: timothy, dactyls glomerata and grass. one of the cohorts tested for more than one of these allergens, so a grass pollen variable was created by using the available variable of these grass allergens. Additional information regarding harmonisation on specific IgE is available in the MeDALL website ( Statistical analysis Prevalence rates of the different diseases (asthma, rhinitis, eczema, asthma and rhinitis, asthma and eczema, rhinitis and eczema, and asthma and rhinitis and eczema) were obtained both for the pooled cohorts and separately for each cohort. The analysis included a cross sectional and a longitudinal component. The cross sectional analysis consisted of estimating the excess comorbidity at 4 and 8 years of age in the pooled cohort and in the strata defined by IgE sensitisation and parental history of allergies, under the null hypothesis of independence of these diseases. We derived the expected frequencies of the occurrence of each disease and their combinations (asthma, rhinitis, eczema, asthma and rhinitis, asthma and eczema, rhinitis and eczema, and asthma and rhinitis and eczema), assuming the independence of these diseases and using a Binomial distribution under the null hypothesis of independence between diseases. In the Supplemental table 2, the observed frequencies at 4 years of age for eczema, rhinitis and asthma were: 7 49, 4 24 and 15 8 respectively. Using these observed frequencies, we first derived the expected frequency of having the triad (A&R&E) by multiplying the observed frequencies of eczema, rhinitis and asthma. Second, we derived the expected frequencies of the pair wise combinations (A&R; A&E; R&E) as the product of their respective observed frequencies minus the expected frequency of the triad. Finally, we obtained the expected frequencies of having only one entity (A or R or E) as its observed frequency minus the expected frequencies of the pair wise combinations minus the expected frequency of the triad. Relative excess comorbidity was estimated as the ratio of the observed to the expected counts and absolute excess comorbidity was calculated by subtracting the percentage of expected frequencies from the percentage of observed frequencies. They were both obtained for the overall populations and separately for each cohort and age period. If the ratio of observed to expected frequencies is greater than 1 0, there is said to be "excess comorbidity" in the study population; and a ratio less than 1 0 indicates that fewer cases of comorbidity occurred than expected. The overall statistical significance of the observed to expected ratios was tested using chi 2 statistics. S6 To test the extent to which each observed frequency departed from the expected frequency, we calculated the individual cell standardised residuals and plotted them using a dropped line plot (with critical values set at 1 96 and +1 96) (Supplemental figure). The process involved standardising the residuals for each cell by dividing the difference between observed and expected frequencies by the square root of the expected frequencies. egative residuals indicate that observed frequencies are less common than expected, while positive residuals indicate that observed frequency are more common than expected. The cells with the largest residuals (< 1 96 or > +1 96) indicate where the independence model has a lack of fit, with a level of significance set at We used log-linear regression models (i.e. Poisson regression models for contingency tables) to assess the relationship between the observed diseases at 4 years of age and those at 8 years of age both in pooled and meta analysis. We performed meta analyses to estimate more powerfully the true effect size and to quantify and analyse inconsistency of results across birth cohorts. The cohort specific RR estimates were combined using a random effects model, which considers within cohort and between cohort variation. The results are presented as 95% CI of adjusted RRs. Statistical heterogeneity among studies was assessed using I 2 statistic. To assess the role of atopy both the cross sectional analysis of the comorbidity and the longitudinal log linear models were stratified by IgE sensitisation. Of the children participating at both 4 and 8 years (10107) and analysed longitudinally, 3929 had no information available on IgE. The longitudinal log linear models were also stratified by maternal history of allergies, paternal history of allergies and maternal and/or paternal history of allergies. We created 20 imputed datasets through the method of chained equations. S7 The analysis of the multiply imputed datasets allowed us to assess the effect of missing data on the results and increased our statistical power. Variables used for the 2

4 imputation models, when available at 4 and 8 years of age, were the following ones: cohort specific, wheezing ever, wheezing attacks in the last 12 months, wheezing after exercise, asthma treatment in the last 12 months, asthma onset before the age of 2 years, bronchitis or bronchiolitis ever, cough at night ever, sneezing or a runny or blocked nose ever, sneezing or a running or blocked nose in the last 12 months, itchy watery eyes in the last 12 months, allergic rhinitis ever, rhinitis onset before the age of 2 years, itchy rash (coming and going for at least 6 months) ever, itchy rash (coming and going for at least 6 months) in the last 12 months, affected areas by this itchy rash, itchy rash onset before the age of 2 years, eczema ever, urticaria ever, food allergy ever, being positive to at least one of the following specific IgE allergens: house dust mite, cat dander, birch pollen, grass pollen, milk or egg; being positive to total IgE, age, weight, height, sex, socioeconomic status, maternal smoking during pregnancy, maternal symptoms of allergic diseases and paternal symptoms of allergic diseases. The analysis of the imputed datasets provided very similar results (supplemental table 3). We performed sensitivity analyses to explore the robustness of the findings and to avoid misclassification bias by increasing the specificity of IgE tests. Additional analyses were conducted using two different cut off points of serum specific IgE concentrations: 0 70 and 3 5 ku A /l (Supplemental table 5A), maternal and paternal asthma (Supplemental table 5B) and parental history of allergies (Supplemental table 5C), and after combining serum specific IgE and total IgE (Supplemental table 5D). For example, sensitised children to IgE 0 70 was defined as having specific IgE concentration 0 70 ku A /l and < 3 50 ku A /l in at least one of the tested specific allergens. All analyses were performed using Stata 12 (StataCorp Stata Statistical Software: Release 12. College Station, TX: StataCorp LP) and R ( Supplemental Results Potential confounders were tested initially by bivariate tables with both the outcome and the exposure variables; these confounders were considered for adjustment if they were related to the outcome and/or the exposure variables. In the adjusted model, none of the confounders were statistically significant and the overall dose response pattern did not change (Supplemental table 3). Maternal smoking ever and paternal smoking ever reduced the sample size of the models. We decided not to include them in the final model. Sensitivity analysis As shown in supplemental table 5D there was hardly any change in the RRs of the longitudinal model when total IgE was used in combination with the specific IgEs. As shown in supplemental table 7, despite the variability in the RRs derived by the random effects model, they followed the same pattern as in the pooled analysis, particularly in the largest cohorts. As the sample size was very small for some of the cohorts we cannot ascertain the sources of heterogeneity (I 2 around 95% p<0.0001). However it is quite likely that several aspects could have contributed to heterogeneity such as differences in geographical distribution or sample size. Supplemental Discussion Strengths and limitations of the study We classified the diseases by means of international well established symptom-based questionnaires that have been extensively validated in previous ISAAC studies for the definition of asthma, S8 rhinitis S9 and eczema. S10 For eczema, though the ISAAC symptom based questions are sufficiently precise for comparisons between populations, its diagnostic precision at the individual level is limited. S10 Unfortunately, in most of the cohorts standardised skin examination protocols were not used. However, a particular problem arises if the classification error for one of the diseases depends on the presence or absence of the other diseases or their surrogates, leading to differential misclassification due to comorbidity. Thus we cannot rule out that differential misclassification could have occurred in our study as it is likely to have occurred in other studies assessing comorbidity. Although the bias caused by differential misclassification can either exaggerate or underestimate associations under study and is not predictable S11 we believe that it may be unlikely to totally account for the observed excess risk of comorbidity given (i) the large magnitude of such excess risk/associations, larger than that found in most epidemiological studies, (ii) the use of questionnaires that have been widely validated in many different languages, subgroups of population or cultural backgrounds, (iii) minimisation of random variability and selection bias by using a large pooled analysis of population based cohorts, (iv) the observed negligible role of confounding another potential source of bias in our study, and (v) the existence of epidemiological and mechanistic evidence suggesting a true relationship between asthma, rhinitis and eczema. 3

5 Supplemental Table 1. Missing values for children participating in the analysis at age 4 and 8 years Participants at 4 years Participants at 8 years = = Age (months) 249/16147 (1 5) 29/11080 (0 3) Sex, female 0/16147 (0) 0/11080 (0) IgE (ku A /l) 8970/16147 (55 5) 4590/11080 (41 4) Socioeconomic Status 103/16147 (0 6) 73/11080 (0 7) Maternal History of Asthma, yes 165/16147 (1 0) 112/11080 (1 0) Paternal History of Asthma, yes 323/16147 (2 0) 224/11080 (2 0) Maternal History of Allergic Diseases, yes 191/16147 (1 2) 136/11080 (1 2) Paternal History of Allergic Diseases, yes 343/16147 (2 1) 247/11080 (2 2) Maternal Smoking During Pregnancy, yes 195/16147 (1 2) 149/11080 (1 3) Paternal Smoking During Pregnancy, yes 7078/16147 (43 8) 3799/11080 (34 3) Maternal Smoking, yes 7121/16147 (44 1) 5842/11080 (52 7) Paternal Smoking, yes 7116/16147 (44 1) 5910/11080 (53 3) Data are n/ (%). 4

6 Supplemental Table 2. Observed to expected frequencies for each of the conditions at age 4 and 8 years All children 4 years 8 years % Obs % Expect O/E % Obs % Expect O/E one Asthma only Rhinitis only Eczema only Asthma & Rhinitis Asthma & Eczema Rhinitis & Eczema Asthma & Rhinitis & Eczema Total Chi ; p< ; p<0 0001, df = 7 Children with IgE sensitisation 4 years 8 years % Obs % Expect O/E % Obs % Expect O/E one Asthma only Rhinitis only Eczema only Asthma & Rhinitis Asthma & Eczema Rhinitis & Eczema Asthma & Rhinitis & Eczema Total Chi ; p< ; p<0 0001, df = 7 Children without IgE sensitisation 4 years 8 years % Obs % Expect O/E % Obs % Expect O/E one Asthma only Rhinitis only Eczema only Asthma & Rhinitis Asthma & Eczema Rhinitis & Eczema Asthma & Rhinitis & Eczema Total Chi 2, df = ; p< ; p< : number of children irrespective of their IgE status, with IgE and without IgE sensitisation respectively; %Obs: percentage of observed counts; % Expect: percentage of expected counts; O/E: Relative excess comorbitidy was estimated as the ratio of observed to expected counts. For the calculation of the expected frequencies (as described in the in the statistical analysis section in the supplemental appendix) we used the following frequencies of eczema, asthma and rhinitis in children aged 4 years regardless of IgE sensitisation: 7 49, 4 24 and 15 8 respectively. Eczema, asthma and rhinitis included both children with single and combined diseases. 5

7 Supplemental Figure. Standardised residuals of observed vs. expected frequencies for each of the conditions A) B) A) Standardised residuals of observed vs. expected frequencies for each of the conditions at 4 years of age and in children with and without IgE sensitisation; B) Standardised residuals of observed vs. expected frequencies for each of the conditions at 8 years of age in children with and without IgE sensitisation. Standardised residuals for each cell were obtained by dividing the difference between observed and expected frequencies by the square root of the expected frequencies. Dashed lines: 1 96, +1 96; grey line and dot: non significant standardised residual; black line and dot: significant standardised residual. A, asthma; R, rhinitis; E, eczema; A&R, asthma and rhinitis; A&E, asthma and eczema; R&E, rhinitis and eczema; A&R&E, asthma and rhinitis and eczema; Overall comorbidity, aggregate category including all comorbidities. 6

8 Supplemental Table 3. Log linear models of the associations between each of the conditions at 4 years and E, R & A comorbidity at 8 years in all children, and adjusted by confounders Crude model With Cohort specific With socioeconomic Status With maternal smoking during pregnancy With paternal smoking during pregnancy With maternal smoking ever With paternal smoking ever With age at follow up = 8366 = 8366 = 8322 = 8250 = 5394 = 3814 = 3815 = 8344 = 8366 one Asthma 12 5 ( ) 12 8 ( ) 12 5 ( ) 12 6 ( ) 11 9 ( ) 13 8 ( ) 13 8 ( ) 12 2 ( ) 12 3 ( ) Rhinitis 17 1 ( ) 16 9 ( ) 16 8 ( ) 17 3 ( ) 15 5 ( ) 30 5 ( ) 29 8 ( ) 17 3 ( ) 17 0 ( ) Eczema 6 6 ( ) 7 0 ( ) 6 6 ( ) 6 8 ( ) 6 6 ( ) 10 3 ( ) 9 8 ( ) 6 6 ( ) 6 7 ( ) Asthma & Rhinitis 43 4 ( ) 44 4 ( ) 45 3 ( ) 45 3 ( ) 48 1 ( ) 68 3 ( ) 69 0 ( ) 42 6 ( ) 43 0 ( ) Asthma & Eczema 40 7 ( ) 41 7 ( ) 41 0 ( ) 41 0 ( ) 43 0 ( ) 52 3 ( ) 51 7 ( ) 39 3 ( ) 40 0 ( ) Rhinitis & Eczema 36 2 ( ) 36 0 ( ) 36 2 ( ) 36 7 ( ) 34 8 ( ) 41 3 ( ) 43 1 ( ) 35 3 ( ) 35 9 ( ) Asthma & Rhinitis 63 5 ( ) 63 5 ( ) 65 4 ( ) 64 3 ( ) 67 1 ( ) 87 2 ( ) 87 0 ( ) 63 4 ( ) 61 9 ( ) & Eczema Cohorts: MAS 1 BAMSE 0 7 ( ) PIAMA 0 7 ( ) LISAplus 0 4 ( ) GIIplus 0 7 ( ) Socioeconomic Status Low 1 Medium 0 9 ( ) High 1 0 ( ) Maternal Smoking 1 1 ( ) During Pregnancy Paternal Smoking 1 1 ( ) During Pregnancy Maternal Smoking 1 1 ( ) Paternal Smoking 1 2 ( ) Age at follow up 1 0 ( ) Sex 0 9 ( ) With sex 7

9 Supplemental Table 4. Log linear models of the associations between each of the conditions at 4 years and E, R & A comorbidity at 8 years in all children, children with and without IgE sensitisation with imputed data At 4 years At 8 years Two and/or Three Diseases Diseases at 4 y at 8 y (%) All children T = 14674* at 4 y Children with IgE sensitisation T = 4663 at 8 y (%) at 4 y Children without IgE sensitisation T = 9839 at 8 y (%) one (2 3) (6 7) (0 5) 1 Asthma only (18 1) 7 9 ( ) (36 2) 5 4 ( ) (6 9) 14 0 ( ) Rhinitis only (28 9) 12 6 ( ) (49 0) 7 3 ( ) (9 4) 19 0 ( ) Eczema only (10 0) 4 3 ( ) (19 9) 3 0 ( ) (2 8) 5 6 ( ) A & R (64 4) 27 9 ( ) (81 3) 12 1 ( ) 23 7 (28 2) 55 4 ( ) A & E (54 4) 23 6 ( ) (70 5) 10 5 ( ) (31 0) 62 8 ( ) R & E (55 2) 24 0 ( ) (67 1) 10 0 ( ) (29 3) 58 7 ( ) A & R& E (87 8) 38 2 ( ) (94 0) 14 1 ( ) 14 9 (62 1) ( ) T : number of children included in the log-linear models. These log-linear models from imputed data included children, participating at both 4 and 8 years, who had two and/or three diseases (Asthma and Rhinitis, or Asthma and Eczema, or Rhinitis and Eczema, or Asthma and Rhinitis and Eczema) and none of the diseases at 8 years of age. Children with one disease at 8 years were excluded from the model. at 4y: the number of children with the corresponding disease at age 4 years; at 8y (%): number of children with comorbidity at age 8 years and percentage of children that have 2 and/or 3 diseases at age 8 years among children with the corresponding disease at age 4 years; A & R, asthma and rhinitis; A & E, asthma and eczema; R & E, rhinitis and eczema; A & R & E, asthma and rhinitis and eczema. 8

10 Supplemental Table 5A. Log linear models of the associations between each of the conditions at 4 years and E, R & A comorbidity at 8 years in children sensitised to IgE levels of 0.35, 0.70, 3.5 At 4 years At 8 years Two and/or Three Diseases Diseases Children with IgE sensitisation ( 0.35) = 1587 Children with IgE sensitisation ( 0.70) = 1264 Children with IgE sensitisation ( 3.5) = 820 at 4 y at 8 y (%) at 4 y at 8 y (%) at 4 y at 8 y (%) one (5 3) (6 7) (10 1) 1 Asthma only (41 7) 7 8 ( ) (43 1) 6 4 ( ) (46 6) 4 6 ( ) Rhinitis only (44 4) 8 4 ( ) (47 1) 7 0 ( ) (57 7) 5 7 ( ) Eczema only (20 5) 3 9 ( ) (24 5) 3 6 ( ) (29 7) 2 9 ( ) A & R (86 7) 16 3 ( ) (100) 15 6 ( ) (100) 10 3 ( ) A & E (75 6) 14 2 ( ) (76 2) 11 4 ( ) (88 2) 8 7 ( ) R & E (59 4) 11 2 ( ) (66 7) 9 9 ( ) (69 2) 6 8 ( ) A & R& E (100) 19 7 ( ) (100) 15 6 ( ) (100) 10 3 ( ) These log linear models included 1587, 1264 and 820 children sensitised to IgE levels of 0.35, 0.70 and 3.5 respectively, participating at both 4 and 8 years, who had two and/or three diseases (Asthma and Rhinitis, or Asthma and Eczema, or Rhinitis and Eczema, or Asthma and Rhinitis and Eczema) and none of the diseases at 8 years of age. Children with one disease at 8 years were excluded from the model. at 4y: the number of children with the corresponding disease at age 4 years; at 8y (%): number of children with comorbidity at age 8 years and percentage of children that have 2 and/or 3 diseases at age 8 years among children with the corresponding disease at age 4 years; A & R, asthma and rhinitis; A & E, asthma and eczema; R & E, rhinitis and eczema; A & R & E, asthma and rhinitis and eczema. 9

11 Supplemental Table 5B. Log linear models of the associations between each of the conditions at 4 years and E, R & A comorbidity at 8 years in children with or without maternal and/or paternal asthma At 4 year At 8 years Two and/or Three Diseases Maternal and/or paternal asthma (yes) Maternal and/or paternal asthma (no) Diseases = 1266 = 7041 at 4 y at 8 y (%) at 4 y at 8 y (%) one (3 3) (1 2) 1 Asthma only (28 9) 8 7 ( ) (14 0) 11 6 ( ) Rhinitis only (39 3) 11 8 ( ) (19 8) 16 4 ( ) Eczema only (20 3) 6 1 ( ) (7 7) 6 4 ( ) A & R 12 7 (58 3) 17 5 ( ) (68 2) 56 5 ( ) A & E (63 6) 19 1 ( ) (58 7) 48 7 ( ) R & E 17 9 (52 9) 15 9 ( ) (54 4) 45 1 ( ) A & R & E (100) 31 4 ( ) (90 0) 74 6 ( ) This log linear model includes 1266 children with positive maternal and/or paternal history of asthma and 7041 children with no maternal an no paternal history of asthma, participating at both 4 and 8 years who had none, two and or three diseases (Asthma and Rhinitis, or Asthma and Eczema, or Rhinitis and Eczema, or Asthma and Rhinitis and Eczema) diseases at 8 years of age. Children with one disease at 8 years were excluded from the model. at 4y: the number of children with the corresponding disease at age 4 years; at 8y (%): number of children with comorbidity at age 8 years and percentage of children that have 2 and/or 3 diseases at age 8 years among children with the corresponding disease at age 4 years; A & R, asthma and rhinitis; A & E, asthma and eczema; R & E, rhinitis and eczema; A & R & E, asthma and rhinitis and eczema. 10

12 Supplemental Table 5C. Log linear models of the associations between each of the conditions at 4 years and E, R & A comorbidity at 8 years in children with or without maternal and/or paternal history of allergic diseases Diseases At 4 year Maternal and/or paternal history of allergic diseases (yes) = 4780 at 4 y at 8 y (%) At 8 years Two and/or Three Diseases Maternal and/or paternal history of allergic diseases (no) = 3515 at 4 y at 8 y (%) one (1 9) (1 0) 1 Asthma only (21 3) 11 0 ( ) 79 9 (11 4) 11 6 ( ) Rhinitis only (31 0) 16 0 ( ) 25 2 (8 0) 8 1 ( ) Eczema only (12 1) 6 3 ( ) (6 0) 6 1 ( ) A & R (70 8) 36 7 ( ) 10 5 (50 0) 50 8 ( ) A & E (64 0) 33 2 ( ) 18 8 (44 4) 45 2 ( ) R & E (59 6) 30 9 ( ) 16 6 (37 5) 38 1 ( ) A & R & E (94 1) 48 8 ( ) 4 4 (100) ( ) This log linear model includes 4780 children with positive maternal and/or paternal history of allergic diseases and 3515 children with no maternal and/or paternal history of allergic diseases, participating at both 4 and 8 years who had none, two and or three diseases (Asthma and Rhinitis, or Asthma and Eczema, or Rhinitis and Eczema, or Asthma and Rhinitis and Eczema) diseases at 8 years of age. Children with one disease at 8 years were excluded from the model. at 4y: the number of children with the corresponding disease at age 4 years; at 8y (%): number of children with comorbidity at age 8 years and percentage of children that have 2 and/or 3 diseases at age 8 years among children with the corresponding disease at age 4 years;. A & R, asthma and rhinitis; A & E, asthma and eczema; R & E, rhinitis and eczema; A & R & E, asthma and rhinitis and eczema. 11

13 Supplemental Table 5D. Log linear models of the association between each of the conditions at 4 years and E, R & A comorbidityat 8 years in (i) all children, (ii) stratified by Specific IgE (variable including any specific IgE available by cohort), and (iii) stratified by specific IgE together with Total IgE (Specific IgE defined as any of the 6 selected allergens) Overall (Table 2) (i) Without missing information to at least one of the available specific IgE (ii) Without missing information to the 6 specific IgE nor to Total IgE (iii) Positive to at least one All egative to any Specific IgE All Positive to Specific IgE or Total IgE egative to Specific IgE or Total IgE Specific IgE Diseases = 8366 = 5010 = 1729 = 3282 = 5011 = 1897 = 3114 one Asthma 12 5 ( ) 11 2 ( ) 8 2 ( ) 14 2 ( ) 11 2 ( ) 9 2 ( ) 13 7 ( ) Rhinitis 17 1 ( ) 14 3 ( ) 8 4 ( ) 22 2 ( ) 14 3 ( ) 9 7 ( ) 19 4 ( ) Eczema 6 6 ( ) 5 9 ( ) 3 9 ( ) 7 6 ( ) 5 9 ( ) 4 0 ( ) 7 5 ( ) A & R 43 4 ( ) 37 0 ( ) 17 7 ( ) 54 8 ( ) 37 0 ( ) 20 0 ( ) 49 1 ( ) A & E 40 7 ( ) 31 6 ( ) 15 2 ( ) 59 2 ( ) 31 6 ( ) 17 1 ( ) 56 6 ( ) R & E 36 2 ( ) 32 4 ( ) 12 1 ( ) ( ) 32 4 ( ) 13 7 ( ) ( ) A & R & E 63 5 ( ) 49 8 ( ) 20 4 ( ) ( ) 49 8 ( ) 22 2 ( ) ( ) Total IgE was categorised as follows: positive total IgE was defined as having IgE concentrations of > 100 U ml -1 and negative total IgE was defined as having IgE concentrations of < 100 U ml -1 ; A & R, asthma and rhinitis; A & E, asthma and eczema; R & E, rhinitis and eczema; A & R & E, asthma and rhinitis and eczema. 12

14 Supplemental Table 6. Children with serum specific IgE sensitisation among those with one or more the three conditions (eczema, rhinitis and asthma) at ages 4 and 8 years per birth cohort. Birth cohorts At 4 years n/ (%) At 8 years n/ (%) Total 569/3762 (15 1) 979/2395 (40 9) PARIS 30/326 (9 2).A. MAS 42/149 (28 2) 80/149 (53 7) BAMSE 249/1055 (23 6) 322/802 (40 2) PIAMA 101/816 (12 4) 200/657 (30 4) LISAplus 45/387 (11 6) 100/187 (53 5) GIIplus 70/542 (12 9) 277/544 (50 9) DARC 32/189 (16 9).A. n at 4y, number of children positive to serum-specific IgE at age 4 years; at 4 years, children with one or more allergy related diseases at age 4 years; n at 8y, number of children positive to serum specific IgE at age 8 years; at 8 years, children with one or more allergy related diseases at age 8 years; %, percentage of children positive to serum specific IgE among children with one or more allergy-related diseases at the corresponding age;.a., not available; BAMSE, Children Asthma, Milieu, Stockholm, Epidemiological Study; DARC, The Danish Allergy Research Centre; GIIplus, German Infant utritional Intervention; LISAplus, Influence of life style factors on the development of the immune system and allergies in East and West Germany; MAS, Multicentre Allergy Study; PARIS, Pollution and Asthma Risk: an Infant Study; PIAMA, Prevention and Incidence of Asthma and Mite Allergy. 13

15 Supplemental Table 7. Meta analysis of the association between each of the conditions at 4 years and presence of E, R & A comorbidity at 8 years MAS BAMSE PIAMA LISAplus GIIplus Models for each disease Sample size Overall = 543 = 2597 = 2201 = 829 = 2196 Asthma only Rhinitis only Eczema only ( ) ( ) ( ) A & R ( ) A & E ( ) R & E ( ) A & R & E ( ) 28 8 ( ) 52 6 ( ) 86 5 ( ) 86 5 ( ) 86 5 ( ) 86 5 ( ) 11 6 ( ) 12 0 ( ) 14 6 ( ) 26 4 ( ) 32 3 ( ) 11 8 ( ) 11 2 ( ) 9 6 ( ) 6 2 ( ) 10 2 ( ) 3 7 ( ) 62 1 ( ) 45 5 ( ) 33 5 ( ) 79 0 ( ) 31 9 ( ) 33 7 ( ) 32 9 ( ) 49 3 ( ) 78 6 ( ) 78 6 ( ) 78 6 ( ) ( ) 18 6 ( ) 41 8 ( ) 27 9 ( ) 49 5 ( ) Each row is a meta analysis for each of the diseases using the random effects statistical model; Adjusted relative risks and 95% confidence interval (CI) derived by random effects model;, sample size of birth cohorts; Overall, relative risks and 95%CI in the meta analysis analysis; BAMSE, Children Asthma, Milieu, Stockholm, Epidemiological Study; GIIplus, German Infant utritional Intervention; LISAplus, Influence of life-style factors on the development of the immune system and allergies in East and West Germany; MAS, Multicentre Allergy Study; PIAMA, Prevention and Incidence of Asthma and Mite Allergy; A & R, asthma and rhinitis; A & E, asthma and eczema; R & E, rhinitis and eczema; A & R & E, asthma and rhinitis and eczema 14

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