EPIDEMIOLOGY

porportion

- a type of ratio that relates a part to a whole. Ex: Proportion of men is 20/100 or 20% A TYPE OF RATIO IN WHICH THE DENOMINATOR INCLUDES THE NUMERATOR (EXPRESSED AS A SINGLE NUMBER) NO. OF DEATHS IN NZ IN 2010 = 28,840 NO. OF DEATHS DUE TO CVD = 11,600 NZ TOTAL POPN IN 2010 = 4.368 MILLION PROPORTION OF DEATHS DUE TO CVD IN 2010: (PROPORTIONS ARE OFTEN MULTIPLIED BY 100 AND EXPRESSED AS PERCENT, MEANING PER 100) IF THE PROPORTION IS VERY SMALL, IT IS MULTIPLIED BY 1000 (OR 100,000), MEANING PER 1000 OR 100,000 OF THE POPN.

Rate

..."a measure of the frequency of a health event in a "defined population in a specified period of time" It is a measure of how rapidly something is happening.

Relative risk is

A measure of the extent to which a group exposed to risk has a higher rate of illness than those not exposed, calculated by dividing the incidence rate amongst those exposed by those not exposed. If the rate is higher among those exposed, it is called a risk factor.

rate

A measure of the frequency of a health event in a defined population , usually in a specified period of time. (A Rate is a ratio, but not a proportion, because the Numerator is the no. of events and the Denominator is a function of both the popn size and the dimension of time Rate deals with change over time (how rapidly something is happening; it typically excludes from the popn being followed those persons who have already experienced the event) Ex. Death rate from CVD in NZ in 2006: 4,368,000 ÷ 1000 = 4,368 11,600 ÷ 4,368 = 2.7 per 1,000

Risk Factors

An attribute or exposure that is associated with an increased probability of particular outcome, such as an occurrence of a disease. E.g. What are the risk factors for SUIDS? (Must be evidence based).

Mortality Rates

Important health indicators globally. Refers to the number of deaths from the illness or disease over a specified time period. The annual mortality rate is an estimate of the risk of death in a given population for that year. Mortality patterns can be described using crude rates, age and sex specific rates or causal rates.

Epidemiology

Is the study of the distributions and determinants of health-related states or events in specified populations, and the application of this study to control health problems. Investigations move from an orderly, sequential process beginning with descriptive research. Progressing to analytic study and Experimental design.

Distribution

It investigates the distribution or patterns of health events in populations and what influences those patterns. Epidemiologists look for: What is the outcome? Who is effected? Where are they? When do events occur? This focus is often called descriptive epidemiology as it seeks to describe a disease in terms of person, place and time.

How RN's use Epidemiology in their Practice

Knowledge: Reading and understanding epidemiological studies. To identify who is at risk in the populations they serve. Public Health Nurses contribute to public health surveillance and disease outbreak investigation. Collection, reporting, analysis, interpretation and communication of epidemiological data as part of their practice. e.g. 1. Practice Nurse: infectious diseases, follow up on cases of tuberculosis, gonorrhoea, 2. School Nurse detection and control of local epidemics. E.g. impetigo and other skin infections(untreated may lead to cellulitis)

ratio

Magnitude of one group Ex: Ratio of men to women: 20:80 or 20/80, or 1:4 or 1/4

infant Mortality rates

The infant mortality rate is, by definition, the number of children dying under a year of age divided by the number of live births that year. The infant mortality rate is also called the infant death rate. The infant mortality rate is an important measure of the well-being of infants, children, and pregnant women because it is associated with a variety of factors, such as maternal health, quality and access to medical care, socioeconomic conditions, and public health practices. SUIDS is a major cause of death in infancy NZ.

Numerator

The number of cases

Denominator

The number of people in the population at risk and the amount of time each was observed. For example, 50 cases of influenza in population of 250 people would be viewed as a serious epidemic, but would indicate a low rate in a population of 250,000.

Determinants

Those factors, exposures, characteristics, behaviours and contexts that determine or influence those patterns. How does it occur? Why are some affected more than others? Determinants may be individual, relational, social or communal or environmental. This focus on causes and associations is called analytic epidemiology as it is directed towards understanding the etiology (origins and causal factors) of the disease. The results of these investigations are used to guide or evaluate policies and programs that improve the health of the population. E.g. current WHO studies on the origins and causal factors (Aetiology) of Avian Flu.

Measures of Morbidity & Mortality

To describe a disease pattern, we should take into account the no. of cases = the numerator and also the no. of people in the population at risk = the denominator Examples: If basing on a simple count of 50 cases of influenza in one month (without knowing the total population) In a small population of 250, it can be viewed as a serious epidemic. In a bigger population of 250,000, it is seen as a low rate.

Risk

as the probability that an event will occur within a specified time period. E.g. Men who had been exposed to asbestos dust over a period of time had an increased risk of developing asbestosis.

nurse role in prevention disease

participate in early diagnosis, notification of specific disease, identify source of infection and method of spread, health education in people in general, control of communable disease.

Crude Death Rate

rates are affected by a number of population characteristics particularly with age structure. For example, Crude Death Rate (per 1,000 people) in New Zealand was last measured at 6.64 in 2010, according to the World Bank. Crude death rate indicates the number of deaths occurring during the year, per 1,000 population estimated at midyear Crude Mortality Rate for N.Z. Crude Death Rate (per 1,000 people) in New Zealand was last measured at 6.64 in 2010, according to the World Bank. Crude death rate indicates the number of deaths occurring during the year, per 1,000 population estimated at midyear. The US had a total population of 299, 398,484 with 2,426,264 deaths. What is the Crude Mortality Rate?

Incidence

used measures of risk calculated from the frequency of a health outcome. refers to the number of new cases of a disease, injury or death in a population during a specified period of time. Is expressed as: The no. of new cases/people with disease/condition in specified period x 1000 or 100,000 ------------------------------------------------------ total 'person-time' at risk during a specified period N.B. 'Person -time' represents the sum of each participant's time at risk

prevalence

used measures of risk calculated from the frequency of a health outcome. refers to the number of people in a defined population who have a specific disease of condition or exposure at a certain point in time: Prevalence is expressed as: The no of existing cases x 1000 or 100,000 ----------------------------------------------- Population at risk at a specific time