# Presentation: 662080

## Epidemiology

- 	**The study of the distribution and determinants of diseases and injuries in human populations**

**Notes:**
Epidemiology is the study of the distribution and determinants of diseases and injuries in human populations.  Epidemiologists describe who has a disease in a population to help identify its causes.  Once the cause is understood, interventions can be developed to prevent, manage, and control the disease.  

Although much is known about asthma physiology, triggers, and treatment, more information is needed to adequately define the scope of the problem across the country and to help pinpoint the actual cause of the disease.  Epidemiologic studies will help us better understand which subpopulations are most severely affected by asthma and why.  That information can help us focus interventions where they can be the most effective.   

## Asthma Prevalence* by AgeUnited States: 1980–1996

- Source:  National Health Interview Survey
- * 12-month prevalence

**Under 18**

**Total**

**18+**

**Notes:**
Historically, the prevalence of asthma has been measured from a question on the National Health Interview Survey.  It is simply the percentage of respondents who answer “yes” to the question “In the past 12 months, has anyone in the family had asthma”?  This slide demonstrates the increase in 12-month asthma prevalence from 1980 to 1996.  After 1996, the question about asthma was changed to ask about lifetime, medically diagnosed asthma. We can no longer measure asthma prevalence comparable to the 12-month prevalence value.  

In the graph, the yellow line indicates the percentage of the U.S. population affected by asthma each year.  The prevalence of asthma increased from 3.1% in 1980 to 5.5% in 1996.  The red and green lines show the difference in the prevalence of asthma for children and adults.  The prevalence of asthma in children (under age 18 years) is higher than it is in adults (age 18 and older).  Asthma is the second most prevalent chronic condition among children.  It results in approximately 14 million days of  missed school each year.  In 1980, 3.6% of children had asthma.  By 1995, the prevalence had increased to 7.5%, or approximately 5 million children. The decline to 6.2% for children in 1996 may be the beginning of a new trend, or it may simply result from random variation due to survey sampling procedures.  In 1996, the sample size was considerably smaller than it was in earlier years, which results in greater variability in estimates.  

## Asthma Prevalence* by SexUnited States: 1982–1996

- Source:  National Health Interview Survey
- * 12-month prevalence

**Male**

**Female**

**Total**

**Notes:**
This graph shows prevalence from 1982 to 1996 by sex.  The green line is for females and the red line is for males.  Before 1992, prevalence differed only slightly.  After 1992, however, the percentages for women were significantly higher than those for men. 

## Asthma Prevalence* by RaceUnited States: 1982–1996

- Source:  National Health Interview Survey
- * 12-month prevalence

**Black**

**White**

**Notes:**
This graph shows the prevalence from 1982 to 1996 by race.  The green line is for whites and the red line is for blacks.  Although prevalence for blacks each year is generally higher than that for whites, it is only significantly higher for 5 of the 15 years---1988, 1991, 1993, 1995, and 1996.  In 1996, the percentage for blacks was 7.0% and the percentage for whites was 5.3%.

## Asthma Prevalence* by RaceAges 5-34, United States: 1980–1996

- Source:  National Health Interview Survey
- * 12-month prevalence

**Black, 5-34**

**White, 5-34**

**Notes:**
Some researchers believe that 5 to 34 is a better age range for studying asthma because it is not confounded by the difficulty of diagnosis in very young children and by other diseases in the older population.  This graph shows 12-month asthma prevalence for those age 5-34 by race.  

## Asthma* Hospital Discharge Rates# by Sex, United States: 1980–1998

- Source:  National Hospital Discharge Survey
- * First-listed diagnosis
- # Age-adjusted to 2000 U.S. population

**Males**

**Females**

**Notes:**
One way we can assess the morbidity, or impact on quality of life, of a particular illness is by determining the rate of hospitalizations from that illness.  From 1980 to 1998, rates were consistently higher for females than for males.  Asthma unnecessarily reduces the quality of life for many people.  For example, hospitalizations for asthma cause people to miss school, work, and other activities.  With proper disease management, however, people with asthma can lead more healthy, active lives.

## Asthma* Hospital Discharge Rates# by Race, United States: 1980–1998

- Source:  National Hospital Discharge Survey
- * First-listed diagnosis
- # Age-adjusted to 2000 U.S. population

**White**

**Other**

**Black**

**Notes:**
From 1980 to 1998, rates were consistently higher for blacks than for whites, and the rates for people of other races varied more because of the relatively smaller size of the population.  

## Asthma* Hospital Discharge Rates by Race, Ages 5-34, United States: 1980–1998

- Source:  National Hospital Discharge Survey
- * First-listed diagnosis

**Black**** ****5-14**

**Black 15-34**

**White 5-14**

**White 15-34**

**Notes:**
Hospitalization rates were consistently higher for children aged 5-14 years than for older children and adults in both racial groups, although for whites the values for the two age groups were fairly close for several years.

## Age-Adjusted* Asthma Mortality Rates by Sex, United States: 1979–1998

**Male**

**Total**

**Female**

- Source: Underlying Cause of Death dataset by the 	 National Center for Health Statistics
- * Age-adjusted to 2000 U.S. population

**Notes:**
During 1993 through 1998, more than 5,000 Americans died from asthma each year.  With proper asthma management, many of these deaths might have been prevented.  The green line is the mortality rate for women and the red line is for men.  The yellow line represents the total population.

Clearly, asthma mortality rates rose during that period.  Women have had higher mortality rates than men since 1981, but they did not have higher prevalence rates than men until after 1991. Most of the increase occurred before 1992 and the increase was greater in women than it was in men. Researchers have not yet determined the cause of the increase. 

## Age-Adjusted* Asthma Mortality Rates by Race, United States: 1979–1998

- Source: Underlying Cause of Death dataset by the
- 	 National Center for Health Statistics
- * Age-adjusted to  2000 U.S. population

**0**

**10**

**20**

**30**

**40**

**50**

**60**

**1979**

**1981**

**1983**

**1985**

**1987**

**1989**

**1991**

**1993**

**1995**

**1997**

**Year**

**Rate per million**

**Black**

**Other**

**White**

**Notes:**
From 1979 through 1998, blacks had higher mortality rates from asthma than whites.  In addition, the increase in mortality rates was greater for blacks than for whites.

## Asthma Mortality Rates by RaceAges 5-34, United States: 1979–1998 

- Source: Underlying Cause of Death dataset by the 	 National Center for Health Statistics
- *  Unreliable (< 20 deaths) 1979–1995

**Black**

**Other***

**White**

**Notes:**
The 5 to 34 year age category is often used because some studies have shown that asthma is most accurately identified as a cause of death in that age group.  Even though the rates are lower than those for all ages combined, asthma mortality rates clearly rose for this age group as well.  Rates for the white and other race categories did not differ for this age group, and the rates for blacks were much higher.

## Costs of AsthmaUnited States, 1980–1998Projection for the Year 2000

- Source:  * Weiss, et al. 1992
- 	** Weiss, et al. 2001**	****	**

**Notes:**
Kevin Weiss, et al. estimated that the cost of asthma in the United States in 1990 was 6.2 billion dollars and in 1998 was 12.7 billion dollars.  Using figures from the later time, costs for 2000 would be around 13.8 billion dollars.  The direct costs of asthma include the costs of asthma management programs, inpatient and outpatient medical care, physician services, emergency visits, ambulance use, drugs, short-term and long-term treatment complications, devices, nursing services, allergy testing, and research.  Some of the indirect costs of asthma include absence from work and school; travel; time waiting for care; and at its most extreme, death.  Costs most difficult to measure are anxiety, pain, suffering, and decreased potential resulting from school absenteeism.

Asthma drains the nation’s health-care budget.  Time, energy, and money are being spent in hospitals and emergency departments where services are expensive and do not address long-term reduction of symptoms.  Although appropriate management of people with asthma should decrease the overall cost of the disease to society, the most important benefit would be the improved health and well being of people with asthma and their families.