epidemiology

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