Over 40 research groups conduct basic neuroscience research and clinical investigations of mental illnesses, brain function, and behavior at the NIH campus in Bethesda, Maryland. Learn more about research conducted at NIMH. Explore the NIMH grant application process, including how to write your grant, how to submit your grant, and how the review process works. Details about upcoming events — including meetings, conferences, workshops, lectures, webinars, and chats — sponsored by the NIMH.
NIMH videos and podcasts featuring science news, lecture series, meetings, seminars, and special events. Information about NIMH, research results, summaries of scientific meetings, and mental health resources. NIMH hosts an annual lecture series dedicated to innovation, invention, and scientific discovery. Contribute to Mental Health Research. Statistics NIMH statistics pages include statistics on the prevalence, treatment, and costs of mental illness for the population of the United States.
Although some epidemiologists use incidence to mean the number of new cases in a community, others use incidence to mean the number of new cases per unit of population. Two types of incidence are commonly used — incidence proportion and incidence rate.
Incidence proportion is the proportion of an initially disease-free population that develops disease, becomes injured, or dies during a specified usually limited period of time.
Synonyms include attack rate, risk, probability of getting disease, and cumulative incidence. Incidence proportion is a proportion because the persons in the numerator, those who develop disease, are all included in the denominator the entire population.
Example A: In the study of diabetics, of the diabetic men died during the year follow-up period. Calculate the risk of death for these men. Example B: In an outbreak of gastroenteritis among attendees of a corporate picnic, 99 persons ate potato salad, 30 of whom developed gastroenteritis. Calculate the risk of illness among persons who ate potato salad. The denominator of an incidence proportion is the number of persons at the start of the observation period.
For example, if the numerator represents new cases of cancer of the ovaries, the denominator should be restricted to women, because men do not have ovaries. This is easily accomplished because census data by sex are readily available.
In fact, ideally the denominator should be restricted to women with ovaries, excluding women who have had their ovaries removed surgically often done in conjunction with a hysterectomy , but this is not usually practical.
This is an example of field epidemiologists doing the best they can with the data they have. Often, the total number of contacts in the denominator is calculated as the total population in the households of the primary cases, minus the number of primary cases.
Consider an outbreak of shigellosis in which 18 persons in 18 different households all became ill. If the 18 households included 86 persons, calculate the secondary attack rate. Incidence rate or person-time rate is a measure of incidence that incorporates time directly into the denominator. A person-time rate is generally calculated from a long-term cohort follow-up study, wherein enrollees are followed over time and the occurrence of new cases of disease is documented.
Similar to the incidence proportion, the numerator of the incidence rate is the number of new cases identified during the period of observation. However, the denominator differs. The denominator is the sum of the time each person was observed, totaled for all persons. This denominator represents the total time the population was at risk of and being watched for disease.
Thus, the incidence rate is the ratio of the number of cases to the total time the population is at risk of disease. In a long-term follow-up study of morbidity, each study participant may be followed or observed for several years.
One person followed for 5 years without developing disease is said to contribute 5 person-years of follow-up. What about a person followed for one year before being lost to follow-up at year 2? Therefore, the person followed for one year before being lost to follow-up contributes 1.
The same assumption is made for participants diagnosed with the disease at the year 2 examination — some may have developed illness in month 1, and others in months 2 through Period prevalence is the proportion of people with a particular disease during a given time period. Prevalence is a useful measure of the burden of disease. Knowing about the prevalence of a specific disease can help us to understand the demands on health services to manage this disease.
Prevalence changes when people with the condition are cured or die. Higher prevalence could mean a prolonged survival without cure or an increase of new cases, or both. Incidence proportion, risk or cumulative incidence refers to the number of new cases in your population during a specified time period. It can be calculated using the following equation:.
Incidence rate incorporates time directly into the denominator and can be calculated as follows:. Person years at risk means the total amount of time in years that each person of the study population is at risk of the disease during the period of interest. Prevalence differs from incidence proportion as prevalence includes all cases new and pre-existing cases in the population at the specified time whereas incidence is limited to new cases only.
The factor connecting prevalence and incidence statistics is the length of time the disease is present for before patients die, or are cured. The number of people that are diagnosed with asthma every year is quite static over time. It has a genetic component, is not being affected hugely by lifestyle or other factors and the rate of cases does not particularly change.
This means that the incidence of the disease stays fairly constant. However, nowadays people do not die of asthma and the number of people with asthma in the population persists until they die of another cause. This is where the incidence can be extremely useful. The incidence of disease is the number of new cases during a specified time period. It is used to describe how quickly the disease occurs in the population and is therefore used to identify increasing transmission and influence decision making about what public health interventions are required to slow this down.
The incidence can be presented as a proportion, for example using the population as a denominator, or as a rate such as person-time, which requires individuals are followed up over time. Going back to the bathtub, water entering the bath through the tap reflects the addition of new cases of disease to the population, the incidence.
In terms of COVID, the incidence can be observed using the number of positive cases identified using laboratory data. The most recent monthly bulletin shows that there were new cases in the most recent week. As with the prevalence, to facilitate comparisons we express this number as a rate per , population an incidence proportion.
The most recent estimate of the incidence rate is
0コメント