The prevalence of bronchial asthma appears to have increased continuously since the 1970s, and bronchial asthma now affects an estimated 4 to 7% of people worldwide. Trends in childhood bronchial asthma from population-based prevalence and routine statistics in India were reviewed. The prevalence of bronchial asthma increased in a secular trend. The prevalence of a life-time diagnosis of bronchial asthma increased in all age groups. The incidence of new childhood bronchial asthma episodes increased. The objective of this study was to determine the prevalence of childhood bronchial asthma in India. Problem Statement: Bronchial asthma prevalence studies lack consistency, possibly because of the ill-defined diagnostic criteria and non standardized study protocols. From some of the important community survey reports, the median prevalence of childhood bronchial asthma in India was determined to be 3.3% (with IQR = 2.3-13.8%). Conclusion: Research during recent years suggests that the prevalence of childhood bronchial asthma has been on the rise. Due to a lack of nationally representative data on the prevalence, risk factors, and prognosis of the disease, there is an urgent need for more public health research in this direction.
Keywords: Bronchial asthma, childhood, prevalence
Childhood bronchial asthma is a very common condition. Its prevalence varies widely from country to country. At the age of 6 to 7 years, the prevalence ranges from 4-32%. The same range holds good for ages 13 and 14. The United Kingdom has the highest prevalence of severe bronchial asthma in the world. 
Childhood bronchial asthma is a chronic disease with an increasing prevalence. It has also increased the number of preventable hospital emergency visits and admissions.  Apart from being the leading cause of hospitalization for children, it is also one of the most important chronic conditions causing elementary school absenteeism.  Childhood bronchial asthma has multifactor causation. Geographical location, environmental, racial, as well as factors related to behavior and lifestyle are found to be associated with the disease. 
In the last 30 years, there has been a steady, relentless increase in the prevalence of childhood bronchial asthma throughout the world. The common characteristics of bronchial asthma include bronchospasm, variable airway narrowing, bronchial hyper-responsiveness, and airway inflammation, but its diagnostic definition is still not clearly defined. Bronchial asthma prevalence studies lack consistency, possibly because of the ill-defined diagnostic criteria and non standardized study protocols. Consequently, an international study was performed using standardized protocol for each center according to the 50-nation International Study of Bronchial Asthma and Allergies in Childhood (ISSAC).  The ISAAC study compared the prevalence rates of bronchial asthma and atopic disease in 155 centers in 56 countries worldwide and was conducted over a period of 1 year in 7,21,601 children aged between 6-7 years and 13-14 years, respectively. Overall, the prevalence of bronchial asthma tended to be greater in English-speaking countries, but the international pattern was suggestive that environmental factors may have played a role in the prevalence of childhood bronchial asthma. Evidence from the ISAAC study also showed that the distribution of childhood bronchial asthma varied between global populations from less than 2% to approximately 33%. Prevalence reaches 17-30% in the UK, New Zealand, and Australia, whereas areas of low prevalence (1-7%) include Eastern Europe, China, and Indonesia. , Furthermore, the prevalence also appears to vary within countries. For example, across India it ranges from less than 5% to approximately 20%. It is unclear why the variation in the prevalence of bronchial asthma is so large. 
In recent years, the majority of bronchial asthma researchers are either using a questionnaire suggested by ISSAC  or the definition of bronchial asthma as modified by the United Kingdom Medical Research Council (MRC). 
The proportion of Indian school children suffering from bronchial asthma has increased to more than double in the last 10 years and has reached its highest level ever. There was a low prevalence of bronchial asthma (2.3-3.3%) in the children surveyed in Lucknow, North India, , but in urban Delhi the prevalence of bronchial asthma was 11.6%.  The prevalence of bronchial asthma in children from rural areas of Ludhiana and Punjab was 2.6% and 1%, respectively.  A study from Bangalore showed 9% and 29.5% prevalence of bronchial asthma during the years 1979 and 1999, respectively. The rise in prevalence over time in Bangalore has been associated with environmental pollution, urbanization, and the change in demography of the city. These factors might be responsible for inter-city variation in the prevalence of childhood bronchial asthma. Among the children who reported ever wheezers, one fourth of them confirmed to be suffering from bronchial asthma later in life. The rest of the children with reported wheezing might have either misclassified wheeze or had episodes of lung infection with bronchospasm or attack of bronchial asthma without recurrence.  A study done on children from urban and rural areas in Tamil Nadu in the age group of 6-12 years showed the prevalence of wheeze to be 18%.  ISAAC Phase I reported a 12-month prevalence of symptoms of wheeze varied between 4.1-32.1% with the lowest rates in India, Indonesia, Iran, and Malaysia and the highest rates in Australia, Brazil, Costa Rica, New Zealand, and Panama in the age group of 6-7 years. In the 13-14 year age group, a 12-month prevalence of symptoms of wheeze ranged from 2.1-4.4% in Albania, China, Greece, Georgia, Indonesia, Romania, and Russia to 29.1-32.2% in Australia, New Zealand, Ireland, and the UK. ,,
More than 6% of the children in the United States have been diagnosed with bronchial asthma with a 75% increase in recent decades. The rate increased to 40% among some populations of children in urban areas. According to the Centers for Disease Control and Prevention’s National Health Interview Surveys, 9% of children in the U.S. below 18 years of age had bronchial asthma in 2001, compared with just 3.6% in 1980. ,
Some of the important community survey reports on the prevalence of childhood bronchial asthma in India are depicted in [Table 1]. The median prevalence from these studies conducted during 1998-2004 was determined to be of 3.3% (with IQR = 2.3-13.8%). The central tendency and dispersion for the total population surveyed and children with bronchial asthma from these studies were 4367 (IQR = 2804.5-12089.5) and 114 (IQR = 94.5-1362.5), respectively. ,,,,,,,
Bronchial asthma affects large numbers of children in India. Though it is usually diagnosed in childhood, there is a reduced occurrence of bronchial asthma in people who were breastfed as babies. Research during recent years suggests that the prevalence of childhood bronchial asthma has been on the rise. Due to the lack of nationally representative data on the prevalence, risk factors, and prognosis of the disease, there is an urgent need for more public health research in this field.
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