Asthma epidemiology and demographics

Editor(s)-in-Chief: C. Michael Gibson, M.S., M.D. [mailto:mgibson@perfuse.org] Phone:617-632-7753; Philip Marcus, M.D., M.P.H. [mailto:pmarcus192@aol.com]; Associate Editor(s)-In-Chief:

Overview
Approximately 300 million people around the world currently have asthma and the number is estimated to increase by additional 100 million by the year 2025. Prevalence of asthma is high among children and females in industrialized nations. International Study of Asthma and Allergies in Childhood (ISAAC), which measured the global prevalence and severity of asthma symptoms in children, demonstrated that the high rates of asthma were noted in countries whose predominant language is English. Puerto Rican people have the highest prevalence of asthma in USA. Asthma accounts for 217,000 emergency room visits and 10.5 million physician office visits every year.

Developed Countries

 * Current research suggests that the prevalence of childhood asthma has been increasing.
 * According to the Centers for Disease Control and Prevention's National Health Interview Surveys, some 9% of US children below 18 years of age had asthma in 2001, compared with just 3.6% in 1980 (see figure).
 * The World Health Organization (WHO) reports that some 8% of the Swiss population suffers from asthma today, compared with just 2% some 25–30 years ago.
 * In the U.S., urban residents, Hispanics, and African Americans are affected more than the population as a whole. Globally, asthma is responsible for 180,000 deaths annually.
 * According to the National Health Statistic Reports, 2009, there is higher prevalence of asthma among people residing in northeast( 9.3%) and midwest (8.8%) regions of USA in comparison to those in south.

Developing Countries

 * Although asthma is more common in affluent countries, it is by no means a problem restricted to the affluent; the WHO estimate that there are between 15 and 20 million asthmatics in India, a country whose per capita income is just around $3,500 USD.
 * On the remote South Atlantic island Tristan da Cunha, 50% of the population are asthmatics due to heredity transmission of a mutation in the gene CC16.
 * Studies suggest that, in developing countries, the rate of asthma increases as communities adopt western lifestyles and become urbanized.

Impact of Age and Gender

 * Males are affected more often during their childhood and the prevalence declines with age. On the contrary, prevalence rises among females steadily through childhood equaling that among males between ages 14-17 years.
 * During adulthood, females report higher current asthma prevalence compared with men.
 * Over 6% of children in the United States have been diagnosed with asthma, a 75% increase in recent decades. The rate soars to 40% among some populations of urban children.



Socioeconomic Factors

 * The incidence of asthma is higher among low-income populations within a society (it is not more common in developed countries than developing countries, ) which in the western world are disproportionately ethnic minorities, and more likely to live near industrialized areas.
 * Asthma has been strongly associated with the presence of cockroaches in living quarters, which is more likely in urban neighborhoods.
 * It is estimated that 15 million disability-adjusted life years (DALYs) are lost worldwide due to asthma per year and is similar to that for diabetes, cirrhosis of the liver, or schizophrenia.
 * Between 2002-2007, asthma cost the US roughly $3,300 USD per person affected with asthma in commoditizations/quality of life measures such as medical expenses, missed school and work days, and early deaths.

Impact of Ethnicity

 * Asthma incidence and quality of treatment varies among different racial groups, though this may be due to correlations with income (and thus affordability of health care) and geography. For example, Black Americans are less likely to receive outpatient treatment for asthma despite having a higher prevalence of the disease. They are much more likely to have emergency room visits or hospitalization for asthma. They are also three times as likely to die from an asthma attack compared to whites.
 * The prevalence of severe persistence asthma is also greater in low-income communities compared with communities with better access to treatment.



Asthma and Athletics

 * Asthma appears to be more prevalent in athletes than in the general population.
 * One survey of participants in the 1996 Summer Olympic Games, in Atlanta, Georgia, U.S., showed that 15% had been diagnosed with asthma and that 10% were on asthma medication. These statistics have been questioned on at least two bases.
 * Athletes with mild asthma may be more likely to be diagnosed with the condition than non-athletes because even subtle symptoms may interfere with their performance and lead to pursuit of a diagnosis. It has also been suggested that some professional athletes who do not suffer from asthma claim to do so in order to obtain special permits to use certain performance-enhancing drugs.
 * There appears to be a relatively high incidence of asthma in sports such as cycling, mountain biking, and long-distance running, and a relatively lower incidence in weightlifting and diving. It is unclear how much of these disparities are from the effects of training in the sport, and from self-selection of sports that may appear to minimize the triggering of asthma.
 * In addition, a variant of asthma called exercise-induced asthma shares many features with allergic asthma. It may occur either independently or concurrent with the latter. Exercise studies may be helpful in diagnosing and assessing this condition.