Table 2.
Summary of epidemiological link between allergy and ASD.
| Title of article | Country | Study design | Sample size | Age range in years | Allergic conditions | Outcome |
|---|---|---|---|---|---|---|
| Is atopy in early childhood a risk factor for ADHD and ASD? A longitudinal study (31) | Taiwan | Longitudinal follow-up study | 14,812 atopic, 6,944 non-atopic | 10–13 at end of follow-up | •Asthma •AR •Allergic conjunctivitis •AD |
•Higher proportion of children with atopic disorders in early life developed ASD in later life (0.8 vs. 0.2%, p < 0.001) compared with children without atopic disorders •Higher proportion of children with atopic disorders in early life developed ADHD (6.3 vs. 2.9%, p < 0.001) in later life compared with children without atopic disorders •Increase in atopic comorbidities increased the risk of ASD development in children (HR: 4.29, 95% CI: 2.25–8.19 for children with four atopic conditions compared with HR: 2.14, 95% CI: 0.90–5.11 for children with only 1 atopic condition) |
| Comorbidity of atopic disorders with autism spectrum disorder and attention deficit/hyperactivity disorder (32) | Taiwan | Population-based longitudinal cohort study | 387,262 with AD, 387,262 without AD | 6–10 at end of follow-up | •AD •AR •Asthma |
•AD diagnosis before 2 years of age was associated with higher risk of ASD (HR: 1.10; 95% CI: 1.03–1.18) and ADHD (HR: 1.16; 95% CI: 1.13–1.19) development •Early onset of respiratory diseases before 2 years of age was associated with higher risk of ASD (HR: 1.49; 95% CI: 1.35–1.64) and ADHD (HR: 1.68; 95% CI: 1.62–1.75) development |
| Increased risk of autism spectrum disorder among early life asthma patients: an 8-year nationwide population-based prospective study (33) | Taiwan | Population-based prospective study | 2,134 asthmatic infants and children, 8,563 controls | 8–11 at end of follow-up | •Asthma | •Higher proportion of children with asthma in early life developed ASD in later childhood (1.3% vs. 0.7%, p = 0.007) compared with children without asthma. •After adjustment for age, gender, urbanization level, and allergy comorbidities, infants and children with asthma had an increased risk of ASD development in later life (HR: 2.01, 95% CI: 1.19–3.40) •Asthmatic subjects who later developed ASD entered asthma remission at an older age as compared with non-ASD asthmatic subjects (5.41 ± 3.09 vs. 4.30 ± 3.04 years, p = 0.059) •Asthmatic subjects who later developed ASD experienced an increased duration of asthma (3.83 ± 3.25 vs. 2.97 ± 2.94 years, p = 0.132) as compared with those without ASD |
| Association of food allergy and other allergic conditions with autism spectrum disorder in children (34) | United States | Cross-sectional population-based surveys | 199,520 children | 3–17 | •Food allergy •Respiratory allergy •AD or other skin allergy |
•Increase in weighted prevalence of reported food, respiratory, and skin allergies in children with ASD (11.25, 18.73, and 16.81%, respectively), as compared with children without ASD (4.25, 12.08, and 9.84%, respectively) •Significantly positive association between food allergy (OR: 2.29; 95% CI: 1.87–2.81), respiratory allergy (OR: 1.28; 95% CI: 1.10–1.50), and skin allergy (OR: 1.50; 95% CI: 1.28–1.77) and ASD after adjusting for sociodemographic data and other allergies •OR of ASD was 1.82, 95% CI: 1.62–2.04 (p < 0.001) in children with allergy as compared with those without |
| Allergic disease and low ASQ communication score in children (35) | United States | Cross-sectional population-based surveys | 715 children | Birth to 8.5 ASQ score taken at age 3; food allergy reported at ages 3 and 6 |
•AD •Food allergy •Asthma |
•Higher proportion of children with lower ASQ score were diagnosed with ASD by age 8 compared with those with normal scores (11.1 vs. 1.2%; p < 0.001), •Higher proportions of children with lower ASQ score reported having food allergy at age 6 (17.6% for low ASQ score group vs. 4.7% for normal development group; p = 0.007) •Children with food allergy at ages 3 or 6 were approximately three times more likely to have lower ASQ scores (p = 0.030) •Children with AD diagnosis at age 3 were twice as likely to have a low ASQ score (p = 0.054) as compared with those without AD |
| Asthma and allergies in children with autism spectrum disorders: results from the CHARGE Study (36) | United States | Population-based case–control study | 560 ASD, 391 controls | 2–5 at study enrolment | •Asthma •Food allergy |
•Risk of asthma did not differ in ASD and non-ASD subjects (16%, p = 0.93) •Children with ASD were two times as likely to report having food allergies (Adj OR: 2.23, 95% CI: 1.28–3.89) |
| Co-occurrence of autism and asthma in a nationally representative sample of children in the United States (38) | United States | Cross-sectional population-based surveys | 77,951 children | 3–18 | •Asthma | •Risk of asthma is higher in children with ASD after adjustment for sociodemographic factors, body mass index, prior brain injury, and exposure to passive smoke (Adj OR: 1.19, 95% CI: 1.03–1.36) |
AD, atopic dermatitis; AR, allergic rhinitis; ADHD, attention-deficit hyperactivity disorder; Adj OR, adjusted OR; ASD, autism spectrum disorder; ASQ, Ages & Stages Questionnaire; HR, hazard ratio; OR, odds ratio.