Association between asthma and attention-deficit hyperactivity disorders in children: Potential risk factors

Abstract

Background: Childhood asthma is common in children. It might be associated with behavioral abnormalities of inattention, irritability, or hyperactivity. These abnormalities form the major components of attention deficit hyperactivity disorder (ADHD). Allergic diseases and ADHD are common pediatric conditions associated with learning difficulties and sleep disturbances. There are conflicting research data regarding the association between ADHD and atopic disorders. Aim: The objective of this study was to examine the potential risk factors, especially investigate vitamin D deficiency a strong contributing factor in asthmatic children with ADHD. Design: This was a case-control study. Settings: Hamad General Hospital, Rumeilah Hospital, School Health and Primary Health Care Clinics, Qatar. Subjects and Methods: A total of 520 asthmatic children with ADHD and 520 controls aged 5-16 years old controls were enrolled in this study and matched with age and ethnicity. The study was conducted between June 2011 and September 2013. Data based questionnaire, clinical manifestations, family history, body mass index (BMI), and clinical biochemistry variables including serum 25(OH) vitamin D, calcium, phosphorus, magnesium was obtained. Univariate and multivariate statistical analyses were performed. Results: Severe vitamin D deficiency was significantly higher among asthmatic children with ADHD compared with the healthy controls (18.1% vs. 10.4%; P < 0.001). Furthermore, the proportion of overweight (24.1% vs. 18.1%) and obesity (8.2% vs. 5.4%) was significantly higher among asthmatic children with ADHD than healthy controls (P < 0.001). Mean values of vitamin D (17.25 ± 10.53 vs. 23.91 ± 9.82; P < 0.001), serum iron (81.46 ± 13.61 vs. 87.23 ± 12.46; P < 0.001), hemoglobin (11.68 ± 2.11 vs. 12.87 ± 2.15; P < 0.001), magnesium (0.77 ± 0.12 vs. 0.83 ± 0.13; P = 0.013), potassium (4.22 ± 0.53 vs. 4.58 ± 0.55; P < 0.001), phosphorous (1.53 ± 0.12 vs. 1.66 ± 0.14; P < 0.001) were significantly lower among asthmatic children with ADHD than in controls. There was a significant correlation between vitamin D deficiency and with age (r = −0.224, P = 0.001); calcium (r = 0.256, P = 0.001); phosphorous (r = 0.316, P = 0.001); magnesium (r = 0.288, P = 0.001); and BMI (r = 0.452, P = 0.001) in asthmatic with ADHD children. Vitamin D deficiency (odds ratio [OR] =3.27; P < 0.001), serum iron deficiency (OR = 2.81; P = 0.008), physical inactivity (OR = 2.67; P = 0.005), ferritin (OR = 2.53; P < 0.001) and serum calcium level (OR = 2.04; P < 0.001) were significant leading predictors in asthmatic children with ADHD. Conclusion: The present study revealed that vitamin D was a significant contributing factor in asthmatic children with ADHD followed by serum iron deficiency and physical inactivity compared with healthy controls.