epidemiology measure Dr.Sania .pdf

Epidemiology mesuerment Measurements of mortality, morbidity, disability, measurements of the presence, absence or distribution of the characteristics or attributes of the disease, measurements of medical needs, measurements of the presence absence or distribution of the enviro...

Epidemiology mesuerment Measurements of mortality, morbidity, disability, measurements of the presence, absence or distribution of the characteristics or attributes of the disease, measurements of medical needs, measurements of the presence absence or distribution of the environmental and other factors suspected of causing the disease, measurement of demographic variables. Toolsof measurement 1. Rates 2. Ratios 3. Proportions 1. Rates A rate measures the occurrence of some particular event (development of disease or the occurrence of death) in a population during a given time period. Death rate = Number of deaths in one year X 1000 Mid - year population Death in x year are 1000and the population are 5000 in mild year the death rate is Sani 1000%5000*1000=200 (1) Crude rates: These are the actual observed rates such as the birth and death rates. Crude rates are also known as unstandardized rates. (2) Specific rates: These are the actual observed rates due to specific causes (e.g., tuberculosis); or occurring in specific groups (e.g., age-sex groups) or during specific time periods (e.g.. annual, monthly or weekly rates). (3) Standardized rates: These are obtained by direct or indirect method of standardization or adjustment, e.g., age and sex standardized rates. 2.RATIO Another measure of disease frequency is aratio. It expresses a relation in size between two random quantities. examples include: The number of malaria cases at a certain time sex-ratio, doctor population ratio, child woman ratio, etc The population of x are 5000 have event from january to december as follow Sani Month Mlaria Malaria Tubercl Tuber Other Other cases death oses closes cases deaths cases death Jan 10 0 5 1 150 20 Feb 20 3 10 2 100 10 March 30 6 50 20 300 50 Apr 100 30 20 0 50 0 May 10 0 20 2 40 5 Jun 100 10 50 20 1000 20 July 200 10 100 10 200 5 Aug 1000 200 200 50 100 20 Sept 300 50 100 10 200 10 Oct 100 2 20 5 100 20 Nov 4000 150 50 10 200 20 Dec 300 10 5 0 100 0 Total 2570 471 630 130 2520 180 death rate = all deathes Death rate = Number of deaths in one year X 1000 Mid - year population (470+130+180)*1000\5000=156 Sani 3.PROPORTION A proportion is a ratio which indicates the relation in magnitude of a part of the whole. The numerator is always is usually included in the denominator. Aproportion expressed as a percentage. The number of children with scabies at a certain time x 100 total number of children in the village at the same time MORTALITY The occurrence of death in a population. Mortality data are relatively easy to obtain, and, in many countries, reasonably accurate. Many countries have routine systems for collecting mortality data each year, information on deaths is analyzed and the resulting tabulations are made available by each government. Limitations of mortality data Incomplete reporting of deaths Lack of accuracy:-inaccuracies in the recording of age and cause of death Lack of uniformity:- There is no uniform and standardized method of collection of data Changing:- Changing coding systems and changing fashions in diagnosis may affect the validity. Sani  Diseases with low fatality:- the disease is associatedwith low fatality (e.g., mental diseases, arthritis). MORTALITY RATE 1. Crude death rate The simplest measure of mortality is the crude death rate It is defined as the number of deaths(from all causes) per 1000 estimated mid-yearpopulation in one year, in a given place. 2. Specific death rates When analysis is planned to throw light on aetiology, it is essential to use Specific death rates. The specific death rates may be (a)cause or disease specific e.g., tuberculosis cancer, accident; (b)related to specific groups e.g. age-specific, sex-specific , age and sex specific, etc. 3. Case fatality rate (Ratio) Case fatality rate represents the killing power of a Sani disease.it is simply the ratio of deaths to cases. The time interval is not specified. Case fatality rate is typically used in acute infectious diseases (e.g., food poisoning, cholera,measles) Total number of deaths due to a particular disease X 100 Devided by Total number of cases due to the same disease Total number of deaths due to a particular disease X 100 Total number of cases due to the same disease 4. Proportional mortality rate (Ratio) It is sometimes useful to know what proportion of total deaths are due to a particular cause (e.g.. cancer) or what proportion of deaths are occurring in a particular age group (e.g., above the age of 50 years). Proportional mortality rats expresses the number of deaths due to a particular cause (at in a specific age group) per 100 (or 1000) total deaths. Thus we have: (a) Proportional mortality from a specific disease Number of deaths from the specific disease in a year X 100 devided by Total deaths from all causesin the year Sani Number of deaths from the specific disease in a year X 100 Total deaths from all causes in the year 2. Under 5 proportionate mortality rate Number of deaths under 5 years of age in the given year. X 100 devided by Total number of deaths during the same period Number of deaths under 5 years of age in the given year X 100 devided by Total number of deaths during the same period 3. Proportional mortality rate for aged 50 years and above Number of deaths at persons aged 50 years and above X 100 devided by Total deaths at all age groups in that year 5.Survival rate It is the proportion of survivors in a group, (e.g. of patients) studied and followed over a period tag, a 5 year period. Survival rates have received special attention in cancer studies. Total number of patients alive after 5 years Survival rate X 100 devided by Total number of patients diagnosed or treated Sani Total number of patients alive after 5 years Survival rate X 100 Total number of patients diagnosed or treated MORBIDITY The occurrence of an illness or illnesses in a population. Morbidity has been defined as any departure, subjective or objective, from a state of physiological well-being. The term is used equivalent to such terms as sickness. illness, disability etc. WHO Expert Committee on Health Statistics noted in its 6th Report that morbidity could be measured in terms of 3 units (a) persons who were ill (b)the illnesses (periods or spells of illness) that these persons experienced; and (c) the duration (days, weeks, etc.) of these illnesses INCIDENCE Incidence rate is defined as the number of NEW cases occurring in a defined population during a specified period of time. It is given by the formula : Number of new cases of specific disease during a given time period X 1000 devided by Population at risk during that period Sani Number of new cases of specific disease during a given time period X 1000 Population at risk during that period For example:- if there had been 500 new cases of an illness in a population of 30,000 in a year, the incidence rate would be: 500*1000 300000 = 500/30,000 x 1000 = 16.7 per 1000 per year PREVALENCE The term "disease prevalence" refers specifically to all current cases (old and new) existing at a given point in time, or over a period of time in a given population. (a) Point prevalence (b) Period prevalence (a) Point prevalence Point prevalence of a disease is defined as the number of all current cases (old and new) of a disease at one point of time, in relation to a defined population. several days, or even a few weeks. Point prevalence is given by the formula: Sani Number of all current cases (old and new) of a specified disease existing at a given point in time X 100 devided by Estimated population at the same point in time Number of all current cases (old and new) of a specified disease existing at a given point in time X 100 Estimated population at the same point in time (b) Period prevalence A less commonly used measure of prevalence is period prevalence. It measures the frequency of all current cases (oldand new) existing during a defined period of time (e.g., annual prevalence) expressed in relation to a defined population. cases arising during the year. Period prevalence is given by the formula: Number of existing cases (old and new) of a specified disease during a given period of time interval X 100 devided by Estimated mid interval population at risk Number of existing cases (old and new) of a specified disease during a given period of time interval X 100 Estimated mid interval population at risk Thanks Sani Find out Death rate Incidance rate in may Malaria death rate Ratio death rste Death rate from may to oct Sani