Morbidity

Overview

Morbidity or illness greatly affects an individual's as well as a population's quality of life. When trying to define or measure the factors that cause some individuals to be unhealthy, it is important to also understand the concept of health. The determinants of health have been acknowledged by the World Health Organization (WHO) to include (a) the social and economic environment, (b) the physical environment, and (c) the person's individual characteristics and behaviors. As the leading causes of illness and death have shifted from infectious diseases to chronic diseases, there has been much work to better understand the social determinants of health and the causes of morbidity. Some commonly used indicators of a population's health include the presence of child abuse, poverty, youth suicide, alcohol-related traffic fatalities, teenage drug use, depression; social networks and social capital.

Measures of Morbidity

Since the mid-1800s, conditions affecting health status began to be measured in a routine and systematized manner in the United States. As a result, incidence and prevalence rates have been used to measure the presence and rate of illnesses or conditions that interfere with a population's well-being. The incidence rate is also known as the cumulative incidence or the number of new cases of a disease or condition, and the prevalence rate refers to the number of existing cases of a disease or condition in a population.

The incidence rate can be calculated and used whenever a condition (physical or mental health related) has a defined diagnosis. Incidence rates can also provide a measure of the risk of acquiring a particular condition. An example of the incidence rate of diabetes in a city of 141,000 residents with 535 new cases of diabetes in 2008 would require the following calculation: 535/141,000 = 0.00379 or 3.8 per 1,000 population. Given that the incidence rate of diabetes was 0.4%, if an individual was a member of that population he or she had a 0.4% chance of getting diabetes. It should be [Page 778]cautioned that extrapolating population data to individuals can be misleading because individual risk factors and behaviors vary widely.

The second common measure of morbidity is prevalence. For example, if a researcher was interested in the prevalence of breast cancer among women in a given city with 141,000 residents and there were 5,076 cases of breast cancer during 2008, the prevalence rate would be calculated as follows: 5,076/141,000 = 0.036 or 36 per 1,000 population. Because prevalence also measures the total number of existing cases of a condition in a population, it can be used to determine the burden of that disease on society. In other words, knowing that 36 residents per 1,000 population, or 5,076 residents currently have breast cancer can give some guidance as to the demand for healthcare services as well as the public health programs that should be provided.

...