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Human Health Studies
Published in Barry L. Johnson, Impact of Hazardous Waste on Human Health, 2020
Prevalence is defined as the proportion of ill persons in a population at a given time and is expressed as a simple percentage. Incidence is the rate of development of disease in a population and can either be expressed as incidence density or cumulative incidence. As Dicker (1996) noted, prevalence refers to existing cases of a health condition in a population, and incidence refers to new cases. An estimate of the sample size needed in a study requires some knowledge of the distribution of the outcome variable in the referent population (or in a case-control study, the frequency of exposure) and a decision on the importance of avoiding each of two kinds of error: type I or “alpha” error, which is the error of claiming that the exposure is associated with the outcome when, in fact, it is not and type II or “beta” error, which is reporting that exposure is not associated with the outcome when, in fact, it is. As a general rule, the probability for a type I error should normally not be greater than 5%, and for a type II error, not greater than 20%.
Epidemiology
Published in Samuel C. Morris, Cancer Risk Assessment, 2020
As opposed to incidence, which is the number of new cases developing in a period in a given population, prevalence is the number of people with the disease at a given time in a given population. The cancer prevalence rate is always larger than the cancer incidence rate, since it includes not only those cases which have developed in the immediate year, but all the cases developed in past years who are still alive and in the population. Since it incorporates factors affecting the survival rate following diagnosis and well as possible in-or out-migration from the area following diagnosis of the disease, prevalence rates are more difficult to translate into risk than incidence rates and so are not as useful for risk assessment. The advantage of prevalence rate is that it is easier to ascertain than incidence rates in surveys.
Limitations of epidemiologic exposure studies on the health effects of asbestos
Published in Dorsett D. Smith, The Health Effects of Asbestos, 2015
Occupational epidemiology is the scientific study of the effects of workplace exposure on the frequency and distribution of various diseases or injuries in a given population. Basically, an epidemiologist studies the occurrence, or incidence or number of new cases over the sum of time individuals in the population were at risk for having that event, such as lung cancer in a population of workers such as asbestos textile workers, and then compares the rate of disease such as lung cancer to the rate of lung cancer in the general population or another more typical reference population. The term incidence is defined as the fraction of a study population initially free of disease that develops a condition such as lung cancer over a period of time, commonly expressed as events/person/years. Prevalence is the epidemiological term used to describe the proportion of people possessing a clinical condition at a single point of time.
Injury patterns among national-level athletes in Lebanon: a retrospective study
Published in Research in Sports Medicine, 2022
Lana El Osta, Abdo El Helou, Habib Aimé Hatem, Nada El Osta
Prevalence is the proportion of a population that has a specific disease or injury in a given time period (Jacobsson et al., 2012). In this study, the 1-year retrospective injury prevalence was determined and its 95% confidence interval was calculated. It was defined as a musculoskeletal disorder that made the athlete partially or completely abstains from training or competition in athletics for a 1-week minimum injury period during the past year.
Online sequential monitoring of spatio-temporal disease incidence rates
Published in IISE Transactions, 2020
Due to the importance of early detection of infectious disease outbreaks, some global, national and regional disease reporting systems have been established to collect/provide data about certain measurements of some important diseases. Commonly used measures of disease frequency include prevalence and incidence (Noordzij et al., 2010). The prevalence reflects the total number of existing disease cases, whereas the incidence refers to the number of newly diagnosed cases of a disease. Compared with the prevalence, the incidence is more useful in understanding disease etiology and providing guiding principles for targeting interventions. Thus, it is preferred in many disease surveillance systems. Also, two main types of disease incidence data are available in practice, including (i) number of newly confirmed cases and (ii) incidence rate of a disease. Even though the number of disease cases can provide some useful information about the current burden of a disease, it suffers from the limitation that it cannot distinguish a large population with a low disease rate from a small population with a high disease rate. To overcome this limitation, we can consider the disease incidence rate, defined as the total number of new cases in a region divided by the population of the region in a specific observation time period. This article is motivated by the incidence rate data of the Influenza-Like Illness (ILI), which is a respiratory infection caused by a variety of influenza viruses. A suspect ILI case is defined as a severe respiratory illness with fever (), cough, sore throat, and difficulty in breathing. It is estimated that 15–40% of the population develop illness from influenza each year in the US. About 36 000 people per year die from influenza infection, and about 114 000 people per year have to be admitted to hospital due to influenza infection (Fiore et al., 2010). A traditional method to estimate the incidence rate of ILI is to carry out repeated seroprevalence surveys. However, such surveys are resource-intensive and slow. Thus, they are unfeasible for early detection of disease outbreaks. To overcome that difficulty, the Florida Department of Health has built an Electronic Surveillance System for the Early Notification of Community-based Epidemics at Florida (ESSENCE-FL) recently, which is a syndromic surveillance system for collecting near real-time pre-diagnostic data from participating hospitals and urgent care centers in Florida. Currently, the system collects data from acute care visits to 229 emergency departments and 35 urgent care centers distributed in all counties of Florida, and the collected data are updated once a day. Figure 1 presents the observed incidence rates of ILI for all 67 counties of Florida on June 1, 2012 (a summer time) and December 1, 2012 (a winter time). From the two plots, we can see that the ILI incidence rates in winter were generally higher than those in summer, and the ILI epidemic in some counties (e.g., Liberty county in northwestern Florida) was serious in the winter time.