of 26
7/29/2019 Morbidity Measures2
1/26
Measures of Morbidity
7/29/2019 Morbidity Measures2
2/26
James Maxwell, physicist (18311879)
7/29/2019 Morbidity Measures2
3/26
We owe all the great advances in knowledge
to those who endeavour to find out how
much there is of anything.
James Maxwell, physicist (18311879)
7/29/2019 Morbidity Measures2
4/26
William Thomson,
engineer, mathematician, and physicist (18241907)
7/29/2019 Morbidity Measures2
5/26
If you can measure that of which you speak,
and can express it by a number, you know
something of your subject, but if you cannot
measure it, your knowledge is meager and
unsatisfactory.
William Thomson, engineer, mathematician,
and physicist (18241907)
7/29/2019 Morbidity Measures2
6/26
7/29/2019 Morbidity Measures2
7/26
Sources of data for illness
7/29/2019 Morbidity Measures2
8/26
Measures of Morbidity
Incidence
Prevalence
7/29/2019 Morbidity Measures2
9/26
Incidence
Measured by incidence rate:
the number of new cases of a disease thatoccur during a specified period of time in a
population at risk for developing the disease.
7/29/2019 Morbidity Measures2
10/26
Incidence rate
Cumulative Incidence
Incidence density
7/29/2019 Morbidity Measures2
11/26
Cumulative Incidence
(Number of new cases during a given period of
time/Population at risk during the same time
period) x 1000
7/29/2019 Morbidity Measures2
12/26
Example
Among 60 people attending a 12-month
residential detoxification program in Mysore,
50 tested HIV negative at the start of the
program in January 1998. At the end of the
program in December 1998, 3 of the 50
participants tested positive for HIV.
Calculate the cumulative incidence.
7/29/2019 Morbidity Measures2
13/26
Incidence Density
Number of new cases during a given period
Total person-time of observation
7/29/2019 Morbidity Measures2
14/26
Uses of Incidence rates
Measures the risk of acquiring the disease
To identify the cause or etiology of disease
To explore the relationship between anexposure and the risk of disease
7/29/2019 Morbidity Measures2
15/26
Prevalence
Measured by Prevalence Rate
Divided into two types:
1. Point prevalence rate2. Period prevalence rate
7/29/2019 Morbidity Measures2
16/26
Proportion of individuals in aspecified population at risk whohavethe disease of interest at a
given point in time.
POINT PREVALENCE RATE
7/29/2019 Morbidity Measures2
17/26
Proportion of individuals in a
specified population at risk whohavethe disease of interest over aspecified period of time.
Annual prevalence rate
(When the type of prevalence rate is notspecified it is usually point prevalence)
PERIOD PREVALENCE RATE
7/29/2019 Morbidity Measures2
18/26
Relation between Incidence and
Prevalence
7/29/2019 Morbidity Measures2
19/26
When Insulin was introduced for the first time,
what happened to the prevalence of diabetes?
7/29/2019 Morbidity Measures2
20/26
Relation between Incidence and
Prevalence
Prevalence = Incidence Duration of disease
P= I x D
7/29/2019 Morbidity Measures2
21/26
City Population
screened
Positive CXR for TB
Mysore 1000 100
Mandya 1000 60
7/29/2019 Morbidity Measures2
22/26
City Population
screened
Positive CXR
for TB
Prevalence Incidence
Mysore 1000 100 100 4
Mandya 1000 60 60 20
7/29/2019 Morbidity Measures2
23/26
City Prevalence Incidence Duration
Mysore 100 4 25 years
Mandya 60 20 3 years
7/29/2019 Morbidity Measures2
24/26
Uses of Prevalence rates
Measures -burden of disease in a community.
Eg:
How many people in the community have arthritis?
To determine
-how many clinics are needed
-what types of rehabilitation services are needed
-how many and what types of health professionals areneeded.
Needed for planning health services.
To make future projections and
To anticipate the changes
7/29/2019 Morbidity Measures2
25/26
Exercises-1
In 2005 all the children in Government schools
of Nanjangud were examined for evidence of
leprosy. The procedure was repeated again in
2006. The following were the results:
2005:
a. No. of children on the rolls- 52,600
b. No. of children examined 48,000
c. No. of children found to have active leprosy - 288
7/29/2019 Morbidity Measures2
26/26
Exercise 1 contd
2006:
d. No. of children on rolls 54,000
e. No. of children examined for the first time- 6,000
f. No. of active cases among the above 46
g. No. of children re-examined - 40,000
h. No. of old cases among them (i) Active 40
(ii) Inactive 200
i. No. of new cases among the re-examined - 80