Heart & Stroke Statistics FAQs

What is Prevalence?

Prevalence is an estimate of how many people have a specific disease, condition, or risk factor at a given point in time. Government agencies periodically conduct health examination surveys. Rates for specific diseases are calculated from those surveys. These rates are applied as the population changes for several years, until a new health examination survey is done, and new rates are established. It’s important to realize that the prevalence rates do not change from year to year until there is a new survey. The annual changes in prevalence as reported in Heart Disease and Stroke Statistics Update only reflect changes in the population. It isn't possible to develop a prevalence “trend” by comparing numbers from yearly issues of the publication or its precursors.

What is Incidence?

Incidence is an estimate of how many new cases of a disease develop in a population in a given time period. For some diseases, new and recurrent attacks or cases are combined. The incidence of a cardiovascular disease in the United States is estimated by multiplying the incidence rates reported in community- or hospital-based studies by the U.S. population. The rates are not computed annually; they change only when new data are available. The estimates were revised to reflect the 2000 U.S. Census. Neither the incidence nor the rates should be compared with those in past issues of the Heart Disease and Stroke Statistics Update.

What is Mortality?

Mortality figures are the most accurate data available for assessing the impact of cardiovascular diseases and stroke. These data are compiled from death certificates and are sent by state health agencies to the National Center for Health Statistics. There the information is verified and tabulated by cause of death, age, sex, and race/ethnicity, for the United States and each state. This process is time-consuming. That's why there's about a two-year delay in the mortality statistics found in the Heart Disease and Stroke Statistics Update. Because mortality is considered “hard” data, it's possible to do time-trend analysis and compute percent changes over time.

What are Death Rates?

A death rate is a ratio between mortality and population. National death rates are computed per 100,000 population. Dividing the mortality by the population results in a crude death rate. When summarizing death rates over time or among populations, we compute age-adjusted death rates. These remove the effects from differences in the age distribution of the population over time and among population groups. The year 2000 is the standard year used for age-adjustment.

What about race and Hispanic origin?

Race and Hispanic origin are reported separately on death certificates. This means that mortality data for each race can include persons of Hispanic origin, and mortality data for Hispanic origin can include persons of any race. In Heart Disease and Stroke Statistics Update, unless otherwise specified, deaths of Hispanic origin are included in the totals for whites, blacks, American Indians/Alaska Natives and Asian/Pacific Islanders. Data for Hispanic persons include all persons of Hispanic origin of any race. Data in Heart Disease and Stroke Statistics Update are as reported by government agencies or as reported by specific epidemiological studies. In many cases, data for Hispanics are not available. Data for Mexican Americans is more likely to be reported because data is harder to find for all Hispanics.

What are "Major CVD" and "Total CVD"?

"Major Cardiovascular Diseases," commonly reported by the NCHS, represents ICD codes I00-I78. “Total Cardiovascular Disease” comprises all “Diseases of the Circulatory System” codes (I00-I99). When data are available, we add congenital cardiovascular defects codes (Q20-Q28) to “Total Cardiovascular Disease.”

What are "Diseases of the Heart"?

The National Center for Health Statistics tabulated mortality of "Diseases of the Heart." The term is commonly used in its statistical publications and its compilation of the leading causes of death. This category groups diseases containing words referring to the "heart" and includes:

• Acute Rheumatic Fever/Chronic Rheumatic Heart Diseases (I00-I09)
• Hypertensive Heart Disease (I11) and Hypertensive Heart and Renal Disease (I13)
• Coronary Heart Disease (I20-I25)
• Other Heart Diseases (I26-I51) – includes heart failure

"Diseases of the Heart" is not equivalent to "Total Cardiovascular Disease," which the American Heart Association prefers to use to describe the leading causes of death. "Diseases of the Heart" represents about three-fourths of "Total Cardiovascular Disease" mortality.