Measures of Burden of Disease in a Population


The number of new cases of a disease in a particular population during a specified time period. Incidence is usually expressed per 10,000 or per 100,000 people, over a day, month, year, or longer period.


The total number of cases of the disease in a particular population at a specified instant in time (including new and previously diagnosed cases). Usually expressed as a percentage of the population (for example, 30 cases of prostate cancer in 1,000 male sanitation workers is a 3% prevalence of prostate cancer in the particular population of sanitation workers).

Age-adjusted Rate

Age-adjustment is a statistical process that allows a rate of death, disease, injury or other health outcome to be compared in two populations with different age distributions (NYSDOH, 2008). For example, older folks may have a higher rate of colon cancer than younger people and the youth may have a higher rate of suicide than the elderly. If there is a higher percentage of elderly persons in community A than community B, community A will appear to have higher rates of colon cancer, when the difference may be entirely due to the difference in age distribution. If community B has a higher percentage of adolescents, then community B may appear to have a higher suicide rate for the same reason.

Case Fatality Rate

This is the number of deaths from a disease among patients diagnosed with that disease. For example if 6 children died of asthma in 2008 out of 1,000 asthmatic children in Washington Heights, the case fatality rate would be 6/1000 or 0.6%.

Life Expectancy

This is the average length of survival in a given population. Life expectancy is usually reported as number of years survived since birth, which is the same as the expected age of death. In broader terms, life expectancy is the expected time remaining to live at a given starting age (not just birth). It can be calculated for any given age. For example, Y.S. from our case is a white 24-year-old woman who had a life expectancy at birth of 81.3 years of age. According to the CDC’s 2010 National Vital Statistics Report (Vol. 60, No. 4, 1/11/2012), she can be expected to live another 57.1 years at the time of her 25th birthday. Life expectancy at birth is highly sensitive to the rate of death in the first year of life per number of live births (i.e., the infant mortality rate).

<< Evidence-based Decisions in Preventive Clinical Practice

Applying Quantitative Epidemiology to Preventive Services >>