IMPACTS OF ASTHMA

Given the absence of a definitive laboratory test or biomarker for the diagnosis of asthma, many definitions and methods of data collection have been used and reported in epidemiologic studies in the past. To discuss the topic epidemiologically, asthma is now defined as bronchial hyperresponsiveness in the presence of wheezing in the previous 12 months (Litonjua & Weiss, 2020a).

Asthma Worldwide

Presently, asthma is a major chronic disease, affecting an estimated 262 million people worldwide in 2019. With the number of cases rising, this number is expected to reach 400 million by 2025. Asthma is one of the most common chronic diseases among children and affects all age groups, races, and ethnicities. However, ethnicity and socioeconomic status do influence the prevalence, morbidity, and mortality of asthma throughout the world.

Asthma worldwide accounts for over 15 million disability adjusted years annually and ranks highest for disability among children.

Individuals who live in developed countries have higher asthma prevalence compared to those who have similar genetic predispositions and reside in developing countries. The higher prevalence rates are hypothesized to be more related to environmental and lifestyle causes than genetic differences.

Factors that account for the lower prevalence in developing countries include lower rates of atopy, more breastfeeding, larger household size, and sometimes, rural residency during childhood. Another factor may be substantial underdiagnosis of asthma in some less-developed countries.

Mortality from asthma worldwide is low compared to other chronic diseases, and according to the World Health Organization (WHO) mortality database, South Africa has the highest age-standardized asthma mortality among low- and middle-income countries, while the Netherlands has the lowest among the high-income countries. The WHO estimates that asthma caused 461,000 deaths globally in 2019, with underprescription of inhaled glucocorticoids and insufficient access to emergency medical care or specialist care playing a part in most asthma deaths (WHO, 2021; Enilari & Sinha, 2019; Litonjua & Weiss, 2020a).

Asthma in the United States

Data from the CDC have shown that the prevalence of asthma increased in the United States from the early 1980s to the early 2000s and subsequently decreased slightly (Litonjua & Weiss, 2020a).

Approximately 25 million Americans have asthma (about 1 in 13), including 8% of adults and 7% of children. About 20 million adults ages 18 and over have asthma, and asthma is more common in adult women than adult men. Asthma is the leading chronic disease in children, and currently there are about 5 million children under the age of 18 with asthma.

ASTHMA PREVALENCE IN THE UNITED STATES, 2019

Age (years)	Individuals with Asthma (thousands)
(CDC, 2021a)
0–4	518
5–14	3,725
15–19	1,529
20–24	2,093
25–34	3,575
35–64	9,594
65+	4,069

GENDER

The strongest nonmodifiable factor associated with asthma is gender. As adults, women have an increased asthma prevalence compared to men. Further, women are more likely to have severe asthma, a later onset of asthma, a higher rate of hospitalizations, and higher mortality compared to men (AAFA, 2021a).

ASTHMA PREVALENCE BY GENDER, 2019

Gender		Individuals with Asthma
(CDC, 2021a)
Males (total)		10,487,151
	<18 years	3,123,923
	18+ years	7,364,299
	65+	1,236,000
Females (total)		14,643,981
	<18 years	1,981,487
	18+ years	12,662,493
	65+	2,834,000

Asthma is more prevalent in males in childhood until they reach puberty and more prevalent in females after puberty. This has been explained by smaller airways in relation to lung size in boys compared with girls under age 10 years. This predisposes boys to worsened airway reactivity compared with girls. Boys are also more likely than girls to experience a decrease in symptoms by late adolescence. After puberty, smaller airway caliber is then observed in females. Known differences in asthma may also be due to other factors such as hormonal effects, genetic susceptibility, and immunologic response (Trivedi & Denton, 2019).

Asthma prevalence is increased in very young persons and very old persons because of airway responsiveness and lower levels of lung function. Two thirds of all asthma cases are diagnosed before the patient is 18 years old, and about half of all children with asthma have a decrease or disappearance of symptoms by early adulthood (Morris, 2020).

Women are more likely to be aware of worsening symptoms at times of hormonal change such as puberty, menstruation, pregnancy, and perimenopause. One third of women report worse asthma symptoms before or during a menstrual period. Some women, particularly those with severe asthma, have worse symptoms during pregnancy. Many women do, however, notice an improvement or no change at all when pregnant (Asthma UK, 2020).

Women with severe or poorly controlled asthma during pregnancy might increase the risk of various problems, including:

• Hypertension and kidney damage (preeclampsia)
• Restricted fetal growth
• Premature birth
• Need for cesarean section

In extreme cases, the baby’s life might be in jeopardy (Mayo Clinic, 2020b).

RACE/ETHNICITY

The CDC reports that asthma prevalence in 2019 among respondents diagnosed with asthma was distributed by race and ethnicity as shown in the table below.

ASTHMA PREVALENCE BY RACE/ETHNICITY, 2019

Race/Ethnicity	Asthma Prevalence
(CDC, 2021a)
Puerto Rican	14%
American Indian/Alaska Native	10.7%
Black Non-Hispanic	10.6%
Mexican American	8.4%
White Non-Hispanic	7.7%
Hispanic	6.6%
Asian Non-Hispanic	3.8%

Racial and ethnic disparities in asthma are caused by complex factors including:

• Structural determinants (systemic racism, segregation, and discriminatory policies)
• Social determinants (socioeconomic status, education, neighborhood and physical environment, employment, social support networks, and access to healthcare)
• Biological determinants (genes and ancestry)
• Behavioral determinants (tobacco use and adherence to medications)

Minority populations are impacted by asthma more than the White population in the United States. The population impacted the most are Puerto Ricans.

Non-Hispanic Black people have a higher death rate per thousand (2.3) than non-Hispanic White people (0.8), and Black women have the highest rates of death due to asthma. Non-Hispanic Black people have higher rates of emergency room visits (17.6) compared to non-Hispanic White people (6.4) and higher rates of hospitalizations (88.5) compared to non-Hispanic White people (23.6).

Non-Hispanic Black children have a death rate eight times that of non-Hispanic White children. They are five times more likely to be admitted to the hospital for asthma as compared to non-Hispanic White children.

Black children exposed to secondhand tobacco smoke are at increased risk for acute lower respiratory tract infections, such as bronchitis. Black children living below or near the poverty level are more likely to have high levels of blood cotinine, a breakdown product of nicotine, compared to children living in higher-income families (CDC, 2021a; OMH, 2021; AAFA, 2021a).

GEOGRAPHY

The prevalence of asthma differs based on geography. Related factors include:

• Poverty
• Air pollution, including ozone and small particles
• Pollen levels
• Smoking laws
• Access to specialists

According to the National Health Interview Survey, 2018, the states with the highest prevalence of asthma were:

• West Virginia, 12.3%
• Maine, 12.3%
• Oregon, 11.6%
• Kentucky, 11.6%

The states with the lowest asthma prevalence were:

• Texas, 7.4%
• South Dakota, 7.9%
• Iowa, 7.9%
• Nevada, 8%
• Minnesota, 8.3%

(CDC, 2021a)

Asthma rates in 2018 among children ranged from 5.0% in Nebraska to 10.9% in Washington, D.C. (ALA, 2020a).

Regional trends indicate two “asthma belts” in the United States in the Ohio Valley area and the Northeast Mid-Atlantic region.

• In the Ohio Valley cities of Cleveland, Dayton, Columbus, Louisville, and Detroit, poverty and air pollution are key factors.
• In the Northeast Mid-Atlantic asthma belt, extending from Massachusetts to North Carolina, poverty, air pollution, and access to specialists are key risks.
• The “asthma capital” in the United States is Allentown, Pennsylvania.
  (AAFA, 2021b)

ASTHMA EXACERBATION PREVALENCE 

The latest data from 2018 reports that the number of physician office visits with asthma as a primary diagnosis was 9.8 million for all ages and emergency department visits with asthma as a primary diagnosis was 1.6 million.

The asthma emergency department visit rate per 10,000 population for asthma exacerbation was significantly higher among children (88.1) than among adults (42.1), and among women (50.4) than among men (31.1). The rate significantly decreased with increasing age:

• 62.7 among adults ages 18–34 years
• 36.9 among adults ages 36–64 years
• 18.2 among adults ages 65 years and over

Regardless of age group, the rate of asthma exacerbations was significantly higher among Black persons (163.5), followed by Hispanic persons (59.9), then White persons (31.3) (CDC, 2021b).

ASTHMA MORTALITY

On average, 10 Americans die from asthma each day. In 2019, 3,524 people died from asthma in the United States. Many asthma deaths are avoidable with proper treatment and medical care. Adults are five times more likely to die from asthma than children. Women are more likely to die than men; however, boys are more likely to die from asthma than girls. Black Americans are nearly three times more likely to die from asthma than White Americans (AAFA, 2021b).