Asthma in African Americans: What can we do about the higher rates of disease?
ABSTRACTAfrican Americans not only have a higher prevalence of asthma than whites, they also are encumbered with higher rates of asthma-associated morbidity and death. Factors such as genetics, socioeconomic status, health maintenance behaviors, air quality, and obesity likely contribute in combination to these burdens. Further work is needed to better understand these complex risk factors. To remedy these disparities, we need to ensure that patients at higher risk are given proper care and the knowledge to control their asthma.
KEY POINTS
- To better identify those at risk, researchers are looking at genetic markers such as polymorphisms in ADRB2 and CD14.
- Exposure to tobacco smoke and to cockroach allergen contribute to higher rates of asthma prevalence and morbidity.
- African Americans are more likely to receive suboptimal care, in particular to be misdiagnosed with other conditions, to not receive inhaled corticosteroids, and to not receive proper follow-up.
- Better physician-patient communication is one of the keys to improving this problem.
What is the mechanism?
The underlying pathogenic mechanisms have not been completely elucidated, and they are likely multiple.
Adipokines (cytokines secreted by adipocytes) have been implicated. Two of the most extensively studied adipokines are leptin and adiponectin. Leptin production is increased in obesity, and it has inflammatory effects on both the innate and adaptive immune systems.90 The opposite is true for adiponectin, which may have anti-inflammatory properties and which decreases as the body mass index increases.90 The precise role these molecules may have in lung disease is undergoing further investigation.
Mechanical alterations in lung function may also contribute. Obese people have a lower functional residual capacity and expiratory reserve volume. Breathing with a lower-volume functional residual capacity results in decreased airway diameter and contributes to increased airway resistance.90 The decreased airway diameter may alter the contractile properties of airway smooth muscle and lead to increased airway responsiveness.90 These differences are in addition to the lower mean values of common spirometry indices such as the FEV1 and FVC, found in nonasthmatic African Americans compared with whites.91
Data suggest these differences are primarily due to anthropometric factors, with nutritional and environmental factors playing a less significant role.92 On this basis, the American Thoracic Society recommends applying race-specific reference standards for use with spirometry in order to accurately gauge lung function in African Americans.
APPROPRIATE CARE AND EDUCATION
The cause of greater asthma prevalence and severity among African Americans is multifactorial. It is likely that a number of factors work together, rather than separately, in influencing the development of asthma and its course.
Some risk factors are avoidable, and it is important to identify and ameliorate them. Others are not preventable, but knowledge of them may provide more specific management strategies and may lead to new therapies in the future.
While more work is needed to further unravel the complex risk factors associated with asthma, ensuring that higher-risk patients are provided the appropriate care and the knowledge to help control their disease is a necessary step in improving the disparities in asthma care outcomes.
