Community Medicine Lecture 5 PDF

Community Medicine Dr. ESRA ABDEEN HEALTH MEASURMENT  Health is multidimensional and each dimension is influenced by numerous factors, this means that health should be measured and evaluated in terms of all its dimensions. Dimensions of health include: 1. Physical dimension....

Community Medicine Dr. ESRA ABDEEN HEALTH MEASURMENT  Health is multidimensional and each dimension is influenced by numerous factors, this means that health should be measured and evaluated in terms of all its dimensions. Dimensions of health include: 1. Physical dimension. 2. Mental dimension. 3. Spiritual dimension. 4. Emotional dimension. 5. Social dimension.  PHYSICAL DIMENSHION The physical dimension of health is the easiest to understand. “perfect functioning “ of the body. As state in which every cell and every organ is functioning at the optimum capacity and in perfect harmony with the rest of the body. Signs of physical health in an individual e.g ‘clean skin, bright eye, good appetite and regular activity of the bowel.  How to assess the physical dimension Standardize questionnaire of cardiovascular diseases Standardize questionnaire for respiratory diseases Biochemical and laboratory investigation Nutrition and dietary assessment AT THE COMMUNITY LEVEL BY INDICATORS: Death rate Infant mortality Life expectancy  MEASURMENTS OF HEALTH Basic measurements in (epi) Epidemiologist needs a definition of what to measure and how to measure it, and those definitions must be acceptable, applicable, precise, and valid.  Tools of measurement They are rates, ratios, and proportions. 1. Rate : it measures the occurrence of some particular events in the population during a specific time period EX Death Rate=NO of deaths in one year/mid year population*1000. 2. Ratio : It expresses the relation in size between two random quantities. The numerator is not a component of the denominator. Ex: ratio of WBC to RBC = 1:600. or 1/600 3. Proportion : A ratio which indicates the relation in magnitude of a part of the whole. The numerator is a component of the denominator. EX:NO. of children with scabies at a certin time/total No. of children in the village at the same time *100 Basic Measurements in epidemiology includes the following: 1. Measurement of morbidity 2. Measurement of mortality 3. Measurement of disability 4. Measurement of medical needs, health care facilities, utilization of health services and other health-related events. 5. Measurement of demographic variables  MEASUREMENT OF MORTALITY Mortality data are relatively easy to obtain, and provide starting point for many epidemiological studies; they are the major source for epidemiologist. The basis for Mortality Data is Death Certificate.  Limitation of mortality data: 1. Incomplete reporting of deaths. 2. Lake of accuracy in the recording of age and cause of death 3. Lake of uniformity...no uniform and standardized method of collecting of data 4. Choosing of a single cause of death  MEASUREMENT OF MORTALITY 1-Crude death rate 2-Specific death rate 3- Case fatality rate 4-Proportional mortality rate 5-Survival rate 6-Adjusted or standardized rate  1.Crude Death Rate Simplest measure of mortality rate Defined as : the number of deaths from all causes per thousand estimated midyear population in one year in a given place CDR FORMULA = number of deaths during the year/ midyear population ×1000  Disadvantages of CDR Lack of comparability for communities with population that differ by age , sex, race etc. However they should always be examined first , and later the age specific death rates which are the most useful single measures of mortality.  2. Specific death rate It is essential to use when analysis is planned to throw light on etiology. it may be: a- causes or disease specific , e.g.: TB & Cancer b- related to specific group ,e.g.: age ,sex specific  SDR example(1): specific death date due to TB SDR = number of deaths from TB during a calendar year/ Mid-year population × 1000 example(2): specific death rate of males SDR = number of deaths among males during a calendar year/ Mid-year population × 1000  Advantages of SDR Help us to identify particular groups or group at risk for preventive action. They permit comparisons between different causes within the same population.  3. Case fatality rate: Represents the killing power of disease CFR = total number of deaths due to a particular disease/ total number of cases due to the same disease × 100 CFR is useful for the acute infections such as cholera, food poisoning but the usefulness for chronic diseases is limited because the period from the onset to death is long and variable.  4. Proportional Mortality Rate Proportional mortality rate (PMR) is the proportion or percentage of deaths due to particular cause out of all the total deaths. It measures the disease burden in the community PMR = No. of deaths due to particular cause (MI)/ Total no. of deaths from all causes*100  MEASUREMENT OF MORBIDITY Morbidity is equivalent to sickness, illness, disability, etc. Three aspects of morbidity are commonly measured by morbidity rates or morbidity ratios, and these are: 1-Frequency. 2- Duration. 3- Severity 1- Disease frequency: it is measured by incidence & prevalence rate  Value of morbidity data 1. Health planning: by describing extent & nature of disease load in community. 2. Basic research: by providing more comprehensive & more accurate and clinically relevant information on patient characteristics than can be obtained from mortality 3. Disease prevention: it is the starting point for etiological studies. 4. Monitoring & evaluation of disease control activities.  PREVELANCE 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 Prevalence is of two types: 1. Point prevalence. 2. Period prevalence.  PREVELANCE Point prevalence is given by the formula: = Number of all current cases (old & new) of a specified disease existing at a given point in time /Estimated population at the same point in time X 100 Period prevalence is given by the formula: = Number of all current cases (old & new) of a specified disease existing at a given point in time / Estimated mid-interval population at risk X 100  Prevalence gives total case load and is useful for planning of community services related to the disease When the term ‘Prevalence rate’ is used, without any further qualification, it is taken to mean ‘Point prevalence.  INCIDENCE Is the number of NEW cases occurring in defined population during a specified period of time Incidence Rate = number of new cases of specific Disease during given time period / Population at risk during that Period ×1000  Example If there had been 500 new cases of an illness in the population of 30.000 in a year the incidence rate would be 500/30.000 *1000 = 16.7 per 1000 per year.  Attack Rate: This is the rate at which the disease is spreading and attacking the people in the community (i.e. extent of the epidemic). This incidence is expressed in percentage and not per 1000. This indicator is employed, with reference to acute diseases specially when there is an epidemic. It is the percentage of the population at risk, getting the disease. Attack rate (AR)=No. of new cases occurring during given period of time/Total population at risk during the same period *100  Secondary Attack Rate: is the percentage of exposed persons, developing the disease following exposure to a primary case, within the range of incubation period. SAR=No. of exposed persons developing the disease/Total no. of exposed/susceptible persons*100  The primary case is excluded from both the numerator and the denominator. For example, if in a family of 6 persons consisting of 2 parents (already immune) and 4 children, susceptible to chickenpox, one child develops chickenpox and after sometime 2 children develop among three SAR=2/3*100 =66%  The relation between prevalence and incidence The relation between prevalence and incidence varies between diseases. There may be: a. high prevalence and low incidence, as for diabetes b. low prevalence and high incidence, as for the common cold P=I*D (P prevalence I incidence D Duration )  Example For stable condition Incidence= 10 cases per 1000 population per year Mean duration of disease= 5 years Calculate the prevalence? P= 10 *5 = 50 per 1000 population Relation between prevalence and incidence.  Prevalence Rate Prevalence increased by Prevalence decreased by Longer duration of the disease Shorter duration of the disease Prolongation of life of the patients Improved cure rate of the disease without care Increase in number of new cases (i.e. Decrease in number of new cases (i.e. increased incidence) decreased incidence) Better reporting of cases. Under reporting of cases. INCIDENCE PREVELANCE Refers to occurrence of new cases only Refers to existence of both old and new in a given area, during a given year. cases in a given area, during a given period/point of time Incidence rate is expressed per 1,000 Prevalence rate is expressed per 100 population at risk population at risk Estimated from longitudinal studies. Estimated from cross-sectional studies. Estimation requires exact knowledge of Such knowledge is not required. time of onset of disease. Refers to acute cases having short Refers to chronic cases having long incubation period. incubation period Ex: Rabies, measles, Act GE, etc. Ex: Tuberculosis, leprosy, etc Not influenced by duration of illness. Influenced by not only duration of illness but also by incidence of illness. P = I × D Related terms are attack rate and Related terms are point prevalence and secondary attack rate. period prevalence Incidence rate is an ideal measure to Prevalence is not an ideal measure to study the etiology of a disease study the etiology of a disease Incidence rate helps to evaluate the Prevalence rate helps for health control measures planning