Gambling Disorders Explained: Prevalence Vs. Incidence
To understand how many people in a given area have a gambling problem, we must first understand how gambling disorders are defined and measured. We addressed some of the foundational questions of definition and measurement in the NCRG’s‘Gambling Disorders Explained’ post earlier this year. Now that the definitions have been outlined, we will examine two common methods used to discuss diseases in a population: prevalence and incidence.
When you hear or read that about 1 percent of American adults are diagnosed with pathological gambling, you are hearing a prevalence statistic. Prevalence is a snapshot of the number of people in a population who have a particular disorder at a particular moment in time, and it is most often expressed as a percentage. For example, there were 19.7 million Americans with diabetes in 2009, which constituted a prevalence rate of 6.2 percent (Centers for Disease Control and Prevention, 2011). That is, for every 100 Americans, approximately six had diabetes in 2009. Prevalence data is very common, and when a newspaper or magazine discusses a disease in a population, the author is almost always referring to prevalence data.
Incidence refers to the number of new cases of a disease in a population in a given time period. Continuing with the diabetes example, there were 1,812,000 new cases of diabetes reported in the U.S. in 2009 (Centers for Disease Control and Prevention, 2011), and the incidence rate was 0.88 percent. (Incidence rate is often expressed as incidence per thousand, in this case it would be 8.8 new cases per 1000 Americans.) Incidence rate is best used to track the rate at which new cases of a disease are being reported. For example, the incidence rate for diabetes was 3.5 new cases per thousand in 1980 and was 8.8 new cases per thousand in 2009.
Not only do incidence and prevalence rates measure different variables, but they also are affected differently by changing circumstances. For example, the rate of recovery from a disease affects the prevalence of the disease but not the incidence. Hypothetically, if an instant cure for diabetes was discovered tomorrow, the prevalence of the disease would fall to zero percent and the incidence rate would be unchanged from its previous level. Alternately, if some hypothetical new product caused an instant week-long bout of diabetes for everyone in the U.S., incidence rates would spike to 100 percent while prevalence rates would stay stable.
At present, there are no peer-reviewed studies that examine the incidence rate of gambling disorders to our knowledge. This may be because studies of incidence tend to be expensive and difficult to conduct because they require following a population over the course of time. A quality study of incidence rates for gambling disorders would go a long way to answering fundamental questions about the development of gambling disorders in a population.
Do you have questions or comments about the concepts discussed in this blog? Is there another aspect of research on gambling disorders that you would like to have explained in a Gambling Disorders 360˚ post? Please submit your suggestions in the comments section below.
References
Centers for Disease Control and Prevention. (2011). Diabetes Data and Trends. Retrieved August 23, 2011, from http://apps.nccd.cdc.gov/DDTSTRS/default.aspx
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