MEASURES OF MORBIDITY. Demography and pptx

MEASURES OF MORBIDITY. Demography and pptx

1. MEASURES OF MORBIDITY Madhulipika Giri

2. Morbidity: T he condition of suffering from a disease or medical condition . Any departure that may be subjective or objective from a state of physiological well being. SICKness Illness Disability Three aspects of morbidity are commonly measured1. Frequency-'Incidence' and 'Prevalence'2. Duration - Average duration per case = 'Disability Rate'3. Severity - CFR or Case Fatality Ratio.

3.  What is the need to measure morbidity? 1. To know the 'disease load' in the community, so that we can set priorities and plan efficient health services 2. Research: by comparing high disease load groups with low disease load group, we may identify the 'risk factors' (one or more of these may turn out to be the cause of the disease)Hence, they are starting point for etiological studies . 3. By assessing the disease load at regular intervals, we can monitor and evaluate the health services for disease control

4. Incidence: Definition: The number of NEW cases occurring in a defined population during a specified period of time. Incidence=No of new cases of a specified disease during a given time period/Population at risk during that period X 1000 Note: The Unit of time is essential in expressing a rate E.g. 100 new cases occurred in a population of 50,000 in a year Incidence = 100/50,000 X 1000 = 2 per 1000 per year

5.  Remember:  Incidence rate refers to  Only new cases  During a given time period  In a specified population or 'population at risk'

6. Prevalence:- Refers to all "old and new" cases existing at a given point or period of time in a given population Definition: The total number of all individuals who have an attribute or disease at a particular time (or during a particular period) divided by the population at risk at that time (or mid-way during the period)  Two types:  Point prevalence  Period prevalence

7. Point prevalence :  Number of all current cases (old and new) of a disease at one point in relation to a defined population  Point - a day/ several days/ weeks etc., depending upon the time required to examine the entire population.  Prevalence=Number of all current cases (old and new) of a specified disease existing at a given point in time/Estimated population at the same point in timePrevalence X 1000

8. Period Prevalence:-  measures the frequency of all current cases (old and new) existing during a defined period of time (e.g. annual prevalence) expressed in relation to a defined population  Includes cases:-  Arising before but extending into the year Extending Through the year as well as Cases arising during the year  Period prevalence:-Number of existing cases (old and new) of a specified diseaseduring a given period of time/Estimated mid-year population at riskX 1000 .

9. Significance of Incidence andPrevalence:-  Why do we need to know the incidence and prevalence separately? Because they have different significance anddifferent uses

10. Relationship between prevalence andincidence:-  Prevalence depends upon two factors  - Incidence and Duration of the illness  P=IxD P = Prevalence, I = incidence and D = mean duration  Assuming that: The population is stable Incidence and mean duration remain unchanged.

11. Eg:-Tuberculosis has a long duration.  Hence prevalence of TB >> Incidence of TB  Food poisoning has short duration Hence incidence >> prevalence  Paradoxically, improved treatment of a disease may increase the prevalence if it prevents death without curing the disease  If the new treatment leads to rapid recovery, the prevalence will decrease even if the incidence does not change

12.  YLL(years of life lost) :- The years of life lost (YLL) is a summary measure of premature mortality. YLL estimates the years of potential life lost due to premature deaths. YLL takes into account the age at which deaths occur, giving greater weight to deaths at a younger age and lower weight to deaths at older age.

13. Disability-Adjusted Life Year (DALY):- One DALY can be thought of as one lost year of "healthy life. The sum of these DALYS across the population, or the burden of disease, can be thought of as a measurement of the gap between current health status and an ideal health situation where the entire population lives to an advanced age, free of disease and disability. DALYS for a disease or health condition are calculated as the sum of the Years of Life Lost (YLL) due to premature mortality in the population and the Years Lost due to Disability (YLD) for people living with the health condition or its consequences

14. Contd... Mathematically, a DALY is represented by the equation DALY = YLL + YLD. YLL is calculated as the number of deaths (n) x the standard life expectancy at age of death (L1). This measures the reduction in life expectancy. YLD is the number of new cases of a disease (I) x a disability weight (DW) x the average time a person lives with the disease before remission or death (L2). This measure represents the diminished quality of life experienced for an individual with injury or illness.

15. Contd... AVERAGE LIFE EXPECTANCY HAS INCREASED BUT ARE THESE ADDITIONAL YEARS HEALTHY, PRODUCTIVE AND ENJOYABLE? TO EVALUATE AND COMPARE, HEALTH INTERVENTIONS UNDERGO COST-EFFECTIVENESS ANALYSIS TO MEASURE THE IMPACT ON BOTH THE LENGTH AND THE QUALITY OF LIFE QALYS (QUALITY ADJUSTED LIFE YEAR) AND DALYS (DISABILITY ADJUSTED LIFE YEAR) ARE COMMON TERMS USED WITHIN THIS FRAMEWORK. QALYS ARE A MEASURE OF YEARS LIVED IN PERFECT HEALTH GAINED WHEREAS DALYS ARE A MEASURE OF YEARS IN PERFECT HEALTH LOST. THEY ARE THE MOST FREQUENTLY CITED METRICS FOR RISK-BENEFIT ASSESSMENT.

16. (QALY) -Quality-adjusted life-year:- It is the arithmetic product of life expectancy combined with a measure of the quality of life-years remaining. The calculation is relatively straightforward; the time a person is likely to spend in a particular state of health is weighted by a utility score from standard valuations.