MORBIDITY INDICATORS Assoc. Prof. Petko Salchev, MD

MORBIDITY Morbidity is a deviation, subjective or objective, from the state of physical or psychic wellbeing or from normal function Morbidity in a broad sense represents the sum of all states of illness, registered by the health service and about which there is relevant information, allowing the statistical processing of related data The study of morbidity demonstrates the development of “processes” in public health

Attack rate The specific frequency of disease, an expression of the percentage of exposed population, suffering from a certain disease

Sources of information for the study of morbidity Patients and members of their families Hospital and health related settings Registers of dying, specialized registers – Oncoregister Specialized institutions, dealing in scientific and clinical studies

Morbidity – sources of information and types Type of studied eventPrimary documentStudies: Addressing related morbidityOutpatient listThe number of persons addressing the health service in case of a health problem, as well as the structure of these health problems Hospitalization related morbidityCard for an ill person, that has left stationery The number of persons admitted to hospital, as well as the structure of reasons Mortality related morbidityDeath noteThe number of persons and reasons leading to death Special report forms related morbidity Rapid notification of disease, poisoning, bound for immediate notification The number of persons and structure of disease leading to death Temporary and permanent disability related morbidity Hospital list of temporary disability and TELK Decision The number and structure of persons temporarily or permanently disabled

Main problems concerning data credibility Problems related to registration – the methods of correct identification and coding of diseases Problems related to information flows – the presence of several information flows, related to changes in legislation

Fundamental concepts and methods of measuring morbidity Incidence (fresh) – all newly appeared cases of disease or diseased persons during a given period of time among a set population (exposed to the risk factor/s) Т0Т0 ТnТn Period (from Т 0 to Т n) Fresh case Cumulative incidence rate

Measuring the frequency of disease Incidence = Number of fresh cases for a given period Population at risk for the same period х 10 n for Т 0 Т n Incidence is a measure of the risk for developing a certain disease and represents an interest for the social medicine experts, who study the causes (determinants) of diseases

Prevalence Prevalence is the number of diseased, totally or of given illness, among the population in a given moment - point prevalence, or for a specified period of time - period prevalence, including new, as well as old cases This indicator depends on the duration of disease

Measuring frequency Prevalence = Old and new cases total Population at risk х 10 n for Т 0 Т n Period prevalence = Old and new cases for a defined period Old + new + disease free for the same period х 10 n for Т 0 Т n Point prevalence = Old and new cases total in a defined moment Т 1 Old + new + disease free in the same moment х 10 n for Т 1

Incidence – a graphical model А В С N1N1 N2N2 NмNм new old N 1 – population in the beginning of the year, N 2 - in the end of the year, N m – in a specified moment

Study of the dynamics Number of new cases of tuberculosis in Bulgaria ( ) Source: World Health Organization, Regional Office for Europe. European health for all database (HFA-DB)

Study of the structure Morbidity structure according to hospitalization – 2004