| OCR Text |
Show Morbidity Indicators Several of the consensus indicators report incidence rates of morbidity as opposed to death rates. "Incidence rates" are defined as the total number of new cases of a particular disease per year divided by the population, then multiplied by 100,000 or 10,000. Immediate problems arise when attempting to understand the meaning of trends in the rates. What are required first are clear and common definitions of "new cases" as well as "population". "New cases" mean just among the residents of the population in question. A visitor to the area who contracts the disease and goes to the doctor would not be counted as a new case. Next, the denominator in the equation ("population") can skew the figure as well. To compare figures from year to year with some degree of accuracy the manner in which population statistics are gathered must be similar. For example if tracking the rate of pertussis in the U.S. one year population of the U.S. includes Puerto Rico but the next year excludes it, the comparison may result in a gap which could lead to false conclusions about the rate of pertussis in America. Further, there is always the possibility that the number of new cases is erroneous. This number could be mistaken for many reasons. Two simple reasons are that those without health insurance may not visit a physician and that a case may be diagnosed incorrectly. Yet even with the possibility of error, these rates remain a good indicator of the overall health of the community. Several of the morbidity indicators include incidence charts for specific age groups for a ten-year period. These illustrate the importance of targeting specific age groups particularly at risk, such as preschool and school age children and the elderly. "Prevalence rates" also are frequently used to measure disease conditions in a population, but have not been reported in this section. (Prevalence of risk factors are included in the Risk Factor section of the Review). Prevalence rates measure the total number of existing cases at a given point in time or over a specified period. Thus, they are helpful in measuring the overall health of a population at a point in time, while incidence rates are helpful in measuring changes and in assessing the control of communicable diseases. 102 |
