DEMOGRAPHIC RISK FACTORS AND ASTHMA Putting Demographics to Work to Identify Asthma Risk Factors E-bulletin No. 5: August 7, 2007 Nancy K. Ostrom, MD, CPI Co-Director Allergy and Asthma Medical Group and Research Center University of California, San Diego San Diego, CA

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Understanding the various demographic factors associated with asthma may help in identifying not only those at risk for developing the disease, but also those more likely to experience severe asthma, asthma exacerbations, and hospitalizations.

Although Hispanics generally have lower asthma prevalence and death rates than African Americans or Caucasians,¹ researchers have found variations in risk among the various Hispanic populations, suggesting that national origin also be considered.² Puerto Ricans, for example, suffer from the highest age-adjusted asthma mortality rates (40.9 per million) among the Hispanic populations in the U.S., followed by Cuban Americans (15.8 per million) and Mexican Americans (9.2 per million). In comparison, these rates were 14.7 in Caucasians and 38.1 per million in African Americans.

The role of socioeconomic factors (eg, urban settings, low income, poor education) versus race and ethnicity remains a subject of ongoing debate. A recent study in children showed that an African American or Hispanic child had a greater risk for asthma regardless of whether the child was from an urban or nonurban setting. However, in the same study, a lower socioeconomic status correlated with a greater risk for asthma regardless of ethnicity.³

Gender. In children, the prevalence of asthma is higher in boys than girls until approximately 14 years old.⁴ In adults, asthma prevalence appears to be greater in women than in men. According to 2002 Centers for Disease Control and Prevention (CDC) statistics, women had a 30% higher asthma prevalence, a 40% higher asthma death rate, and a 35% higher asthma hospitalization rate compared with men.⁵ In a U.S. Navy surveillance of asthma, age-adjusted incidence rates of first hospitalization for asthma were 3 times as high in women as in men, and doubled between 1980 and 1999.⁶ In the same study, rates of asthma were twice as high in African American versus Caucasian women.⁶

Modifiable risk factors. Researchers have associated obesity with asthma, particularly in women; this was examined in an earlier bulletin. Likewise, current and former smokers are more likely to have current asthma than individuals who have never smoked.⁷ In children, exposure to second-hand tobacco smoke in utero and in early infancy has been shown to increase dramatically the risk of asthma.⁸ These findings highlight the need to identify and diminish these risk factors.

Looking ahead. A recent study by Kelley et al. found evidence that certain risk factors may vary according to the particular asthma phenotype.⁹ For example, mean body mass index (BMI) was higher among children with nonatopic asthma. Also, child care attendance was a risk factor for frequent respiratory symptoms with no asthma diagnosis. The authors concluded that asthma may actually represent several different clinical entities—each with different risk factors and outcomes—and that a better understanding of these differences may ultimately contribute to better interventions.⁹

References

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