If you wake up in the morning without back pain, consider yourself lucky. According to well-documented studies, approximately one out of every two workers across the country will experience some type of back pain every year. Researchers estimate that 8 out of every 10 people will make it.
Point prevalence is measured at a single point in time (ie, the number of people reporting LBP on the day of a survey). Period prevalence is measured over a specified time period, usually 1 year (ie, those people who report having had LBP in the past 12 months). In contrast, incidence refers to the number of new cases occurring during a period of time among a group initially free of the disorder. The cumulative incidence or lifetime incidence is the total number of people who have or have had the condition during their lifetime. Deyo and Tsui-Wu also refer to this as the cumulative lifetime prevalence. Thus, it appears that there is confusion in the literature with respect to the use of the terms “lifetime incidence” and “lifetime prevalence.” Figure 1 illustrates 10 cases of LBP in a hypothetical population of 20 individuals from 1993 to 1998. Calculations of period prevalence, point prevalence, annual incidence, and cumulative incidence are provided as examples to clarify definitions.