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Epidemiology
October 21, 2014
II. Morbidity and Mortality
Morbidity תחלואה
ותארעהי Incidence
Incidence per 1,000 =
no. of new cases of disease
occurring in the population
during a specified period of time x1000
no. of persons at risk of developing
the disease during that period of time
Annual age-specific incidence rates of reported cases of breast cancer, by
marital status
Cumulative incidence
CI = number of people who develop
disease during a certain period
number of individuals in the
population at the beginning of the
period
Cumulative incidence
Incidence rate measures:
The rate at which new events occur in a population. Incidence rate/density is calculated by:
Number of persons who contract
the disease in a specified period x 10n
Sum of the length of time each
person in the population at risk
of contracting the disease
(person-time incidence)
Example of calculation of disease occurrence
Example of calculation of disease occurrence
Simple incidence:
3 cases in 7 individuals over 7 year
Yearly incidence:
3/7/7=0.06 cases per year (6%/yr)
Incidence density:
3/33 p.yr=0.09 cases per p.yr (9 per 100 p.y)
Cumulative incidence
Is a simpler measure of the occurrence of a disease or new health status.
Unlike incidence rate, it measures the denominator at only one point in time.
Prevalence ותמצאהיPrevalence rate is defined as:
The proportion of the population at risk affected by a disease at a specific point in time
Prevalence rate (P) is calculated by:
P= number of people with disease
or condition at a specific time x10n
number of people in the population
at risk at the specified time
מחלות נבחרות - שיעור הימצאותן של מחלות מבוטחים על פי הרישום בתיקי 100ממושכות, ל-
1996הרופאים בקופת חולים הכללית,
Random Sample of 1740 members of Clalit who visited their doctors at least three times in 2009
Dyslip
idem
ia
Any
chronic
disease
Diabet
es
Hyp
erte
nsio
n
Smok
ing
IHD
Ost
eopo
rosi
sC
ance
r
Ast
hma
Hyp
othy
roid
Pept
ic u
lcer
Dep
ress
ion
Obe
sity
Israel – Results of social survey 2004 prevalence of:
Prevalence of asthma among 17 year olds in Israel
Study population 159,243 consecutive 17-year-old military recruitsAsthma was documented in 8.5% of the male recruits and in 6.7% of the
female recruits
Farfel et al.Ann Allergy ,Asthma,Imm 2010;104:490-5
SES Family size
Prevalence of obesity, OECD , 2011
שיעור המעשנים בקרב המשתחררים 2004-1992מצה"ל, לפי מין,
ICDCדוח שר הבריאות על העישון בישראל, 2005
20
30
40
50
92 93 94 95 96 97 98 99 2000 2001 2002 2003 2004
שנה
חוזא
גבריםנשים
Factors influencing observed prevalence rate
Relationship between incidence and prevalence: I
Relationship between incidence and prevalence: II
Relationship between incidence and prevalence: IV
AIDS היארעות המחלה, הימצאותה-- 1985, 100,000והתמותה ממנה (שיעור ל-
1996(
Mortality תמותה
Routine information Mortality (death) data:
(coded according to the ICD)
Crude mortality rate (CMR)
CMR= total # people dying
total # people• Age-specific rates• Sex-specific rates• Cause-specific rates• Age-standardized rates (also called age-adjusted
rates)
Routine informationתמותת תינוקות
Infant mortality rate:
Death rate up to one year per 1000 live births
Often used as an indicator of “quality” of the health care system
תמותת תינוקות , ישראל
Case fatality rate
Case fatality rate (percent) =
no. of individuals dying during a
specified period of time after
disease onset or diagnosis x 100
no. of individuals with the specified
disease
Comparison of a mortality rate and case-fatality rate
Assume a population of 100,000 people of whom 20 are sick with disease “X” and in 1 year, 18 die from disease “X”
The mortality rate in that year from disease “X” =
18 = .00018 = .018%
100,000
The case fatality rate from disease “X” =
18 = .9 = 90%
20
Relationship between incidence and mortality CFR
Case Fatality EbolaVariation by time and place
Gap between incidence and mortality rates may reflect case fatality
Definition:Life expectancy at birth and ages 40, 60, 65 and 80 is the average number of years that a person at that age can be expected to live, assuming that age-specific mortality levels remain constant
תוחלת החיים
Life expectancy
Israel Health Stats•Obesity (adult prevalence 2008) 26.2%•Maternal Mortality Rate: 7/100,000 live births•Infant Mortality: 4.03/1000•Life expectancy at birth :
Males-78.96 yFemales 83.49 y
•Health Expenditures: 7.8% of GNP
Trends over time
Gender Gap Life Expectancy at birth
Quantifying Burden
YLL = Years of Life Lost
YLD = Years of Life lived with specified level of Disability (0,1)
DALY: Disability Adjusted Life Year: = 1 year lost of healthy life
DALY = YLL + YLD
Health statistics are used for other purposes
Sources of Israeli data• Central Bureau of Statistics למ"ס
• המרכז הלאומי לבקרת מחלות
• Research institutions (Brookdale)
• Academia
One last point
Age matters!
Prevalence of diabetes rate per 100,000 persons- International comparison
Importance & Relevance DIABETES Prevalence
Worldwide
(OECD INDICATORS, ADULTS 20-79 YEARS, 2010)
Prevalence rate of non-insulin-dependent diabetes mellitus in
selected populations
Location/population Age group (years) Prevalence rate(%)
Fiji IndiansIndonesiaIsraelMaltaMexican Americans(USA)NauruPima Indians (USA)USA
20+15+40-7015+25-64
20+25+20-74
13.51.715.97.717.0
24.325.56.9