Risk Factors of Chronic Cough and Wheezing in Outpatient and Hospitalized Children

Wheezing and chronic cough, as the most common respiratory disorders, are multifactorial with different respiratory-associated illnesses, which occur due to different etiologies (1, 2). These appear to be common, with a prevalence of five to seven percent in preschoolers and 12% to 15% in older cases (3). Chronic cough is typically defined as a cough lasting more than four weeks, and wheezing is diagnosed by chest auscultation (4, 5). Probable risk factors of wheezing and chronic cough include smoking, inherited traits, infection of airway at a very young age, bronchitis, air pollution, physical activity, increased sensitivity of the immune system, previous allergic reactions to dust mites, sinusitis, pet dander, cold air and weather changes, hives or eczema, allergic rhinitis, obesity, pneumonia, gastroesophageal reflux disease (GERD), black breed and male gender, which can influence these conditions (6-8). Etiologies of chronic cough in children are quite different from that of adults, so evaluation and management of children should not be based on adult protocols (9). Gastroesophageal reflux, upper airway cough syndrome, and sinusitis are sometimes misdiagnosed, because of associations with chronic cough in adults, but their role in causing chronic cough in children is controversial (10, 11). Child evaluation with chronic cough composed of a detailed history, chest radiograph, physical examination, and spirometry. If the initial evaluation suggests a specific cause, further evaluation is focused on that diagnostic possibility (2). Other diagnoses of chronic cough included chronic and sub-acute infections, aspiration of foreign body, and cough-dominant asthma (12). Red flags included failure to thrive, cough that is unusually frequent and severe, exertional dyspnea, growth retardation, purulent sputum, chest pain, hemoptysis, or hypoxemia (13). Based on the content, we can find the importance of this issue, so this study aimed to investigate risk factors of chronic cough and wheezing in outpatients and hospitalized cases.

In total, 485 children were evaluated. Demographic and social factors had a significant effect on chronic cough and wheezing in children. Age parameter was classified into four groups as follows: 59 children (%12.1) were lower than one year, 130 children (%26.8) were 1 - 3 years, 203 children (%41.9) were 3 - 5 years, and 93 children (%19.2) were more than five years (P = 0.0001). In gender section, 268 children (%55.3) were male and 217 children (44.7) were female (P = 0.0001). In addition, other factors, including BMI, housing status, pet, living area, beetle in living location, type of heating device, consanguineous marriage, education status of fathers and mothers, and smoking in mothers and fathers had a significant effect on chronic cough and wheezing in children (P < 0.05) (Table 1).

Cough status of affected children was evaluated. In the following, important information was presented. Smoke and steam were recorded as the most common etiologies and risk factors of chronic cough and wheezing. Other effective factors included 14% dust, 9% flowers and plants, 10.9% cold air, 5.8% sporting, 4.5% spicy and 35.7% other stimulants foods (P = 0.0001). The most common onset time of symptoms was spring (P = 0.0001), and the most common onset age of chronic cough was 3 - 5 years (P = 0.0001). Also, 173 children (35.7%) had a history of chronic cough in parents (father and/or mother) (Table 2). We evaluated clinical status of children and their parents, including atopic history of children and parents, history of lung diseases in parents, pneumonia, surfactant administration, medications, and chest tube in children. In this regard, 75 children (15.5%) and 309 parents of children (63.7%) had a history of atopy (P = 0.0001). Most common medication was corticosteroid (P = 0.0001) and most common etiology of hospital admission was asthma (P = 0.0001). Other factors had a significant effect on chronic cough and wheezing (P < 0.05) (Table 3).

Feeding status of children was evaluated, and the most common age of complementary feeding was more than six years (P = 0.0001). The most common type of complementary feeding was gruel (P = 0.0001), 272 children (56.1%) had salt in food (P = 0.0001), and 125 children (25.8%) had a history of milk consumption (P = 0.0001) (Table 4). Delivery status of children was evaluated and in total 349 cases (72%) was under cesarean section (P = 0.0001). In body birth weight (BBW) section, six children (1.2%) had very low birth weight (VLBW), 60 children (12.4%) had low birth weight (LBW), and 36 children (7.4%) had high birth weight (HBW) (P = 0.0001). About gestational age, 58 children (12%) were preterm and 12 children (2.5%) were post-term (P = 0.0001) (Table 5).

The findings of this study showed different risk factors of chronic cough and wheezing in outpatients and hospitalized children, so our results confirm most related studies regarding this issue in other countries, and related studies about these risk factors were compared with our results. A study by Weinberger and Abu-Hasan in Turkey was done on 731 children from one month to 8 years who had cough and wheezing. Maximum age of coughing and wheezing was in the range of 3 to 5 years (14). In addition, this was consistent with our study, and 9.41% was in range of 3 to 5 years and the lowest prevalence was related to lower than one year of age. In another study by Sennhauser and Kuhni, 250 children in five to 15 years of age were evaluated. They investigated the prevalence of respiratory disorder and its correlation with gender of children. Of 250 children, 61% were male, and 31% were female (15). In our study, 55.3% were male and 44.7% were female, which confirms the stated study. A study by de Jongste and Shields was conducted in Austria, which demonstrated the effect of smoking on the prevalence of respiratory disorders, as an important risk factor for chronic cough and wheezing (16). In our study, 86.6% of the parents were cigarettes smoker, which is consistent with the study conducted in Austria. In a study conducted in Canada, angiotensin-converting enzyme inhibitors (ACEI) and cytotoxic agents were recognized as important factors involved in the pathogenesis of chronic cough (17), but in our study, most patients did not use any drugs, and 10.7% of patients used non-steroidal anti-inflammatory drugs (NSAID), which may cause cough in children with asthma. Based on low prevalence of high blood pressure (hypertension) in children, this miscorrelation to the study of Canada is predictable. In a study conducted by Murray et al. in 2010 in Italy, the relationship between body mass index (BMI) and respiratory symptoms was investigated in children, and they concluded that increased BMI was associated with respiratory symptoms, particularly wheezing (18). In our study, 78.6% of children had normal range of BMI, and only 8.2% had higher than normal BMI. In two studies carried out in Austria and US, pets and animals were found as important factors in causing chronic cough and atopy in children (19, 20). In our study, 45.6% of children kept animals and birds at home, which confirmed the results of the above-mentioned studies. A study in Austria was conducted on 752 children, one to four years of age, with chronic cough. In this study, atopy history of children and their parents were mentioned as risk factors for chronic cough incidence (20). In our study, 36.6% of children and 15.5% of parents had a history of atopy, which is in agreement with the previous studies. In a study by Menezes, delivery status of children and its correlation with wheezing were evaluated. They found that wheezing was equal in caesarean section and vaginal delivery (21). In our study, 28% of children had CS and 72% had NVD delivery, which was not consistent with the stated study. In a study by Rosenstreich et al. (22), the role of cockroach allergens in children with respiratory symptoms was examined. They showed that 36.8% of children were sensitized to cockroach allergens, and 50.2% of cockroach allergens were found in dust of bedrooms, indicating cockroach allergens are associated with respiratory symptoms in pediatric population. In a study conducted by Robin et al., the correlation between fuel consumption and chronic cough was investigated. They indicated that 60% in case and 10% in control groups had wood fuel, demonstrating its effect on respiratory dysfunction (23). Also, in our study, 49.5% have fuel gas consumption, which is consistent with the mentioned study. In a study conducted in 2007 in Italy, the effect of diet in the development of respiratory symptoms in children was investigated. This study showed that adding salt to food and carbonated beverages is associated with an increased risk of respiratory symptoms (24). In our study, NaCl was added to the food of children as 56.1%, which was consistent with the Corbo study. In a study conducted in 1996 by Zedja et al., formula feeding is known as a risk factor for chronic cough (25). In our study, 25.8% of the children have used formula feeding as a risk factor for chronic cough. In a study conducted in the US in 2009, GERD (27.5%), allergy (24.5%), asthma (12.5%), infection (5%), foreign body aspiration (2.5%), have been identified as etiologies of chronic cough. In general, allergies and asthma form more than 80% of etiology of chronic cough in children (26). In our study, asthma and rhinosinusitis form more than 80% of the etiology of chronic cough cases, which confirms the previous study. Limitations of our study include providing personal satisfaction and failure to cooperate in the study courses. It is recommended to do related case-control studies for better evaluation of these risk factors.