Chapter 3: Measures of Morbidity & Mortality Used in Epidemiology

Question 1

What is a count?

Answer 1

The # of cases involved of a disease
Ex: cases of influenza reported in Westchester County; college dorm residents who had mononucleosis; stomach cancer patients who were foreign born; traffic fatalities in the borough of Manhattan during a 24-hr period

Question 2

Ratio? Types?

Answer 2

A value obtained by diving the 1 quantity by another

• Simple-sex
• Demographic
• Sex ratio at birth

Question 3

Proportions?

Answer 3

A type of ratio in which the numerator is part of the denominator. Can be expressed as a percentage.
Formula: A/ (A+B)
Ex: A is 1,1150 (# of African American boys)
B is 3,180 (# of white boys)
1150/ (1150+3180)= 0.2318 = 23.2%

Question 4

Simple sex ratio

Answer 4

# of male cases to female cases 
Ex: Out of 1000 car fatalities, 950 were men, 50 were women. What's the SSR? (950/50 = 19/1 M to F)

Question 5

Demographic sex ratio

Answer 5

SSR * 100

Ex: (151,781,326/156,964,212)* 100 = 96.7

Question 6

Sex ratio at birth

Answer 6

SSR * 1000

Ex:

Question 7

Rate? Elements?

Answer 7

A type of ratio. The denominator involves a measure of time. Consists of num/deno in which both are calculated in units of time.

• Disease frequency count
• Unit size of the population at risk
• Time period during which the event occurs

Question 8

Prevalence?

Answer 8

of existing cases of a disease or health condition in a population at some designated time

• Describes burden of illness in a pop.
• Guides allocution of resources
• Outcome measures often expressed as 10^n

Question 9

What is point prevalence?

Answer 9

Prevalence at a point in time
Ex: (# of persons ill/total # in the group) from July 13-15
41,837 people were asked if they smoke, 6,234 said yes (6,234/41,837) = 14.9% is the point prevalence

Question 10

What is period prevalence?

Answer 10

Prevalence during a period in time. # of cases in a period of time.
Ex: Have you ever been diagnosed by a physician as having any form of cancer, other than skin cancer?
41,837 people were asked, 2,293 said yes (2293/41837) = 5.5% is the period prevalence

Question 11

What is BMI?

Answer 11

Body mass index; a measure of obesity

Question 12

Incidence?

Answer 12

the number of instances of illnesses commencing, or of persons falling ill, during a given period in a population. A measure of the risk of a specified health-related events

Question 13

Incidence rate?

Answer 13

the rate of development of a disease in a group over a certain time period; period included in the denominator
-(# of new cases/total pop. at risk) * 10^n
-time: the period during which the cases accrue
Ex: 1,085 new cases of breast cancer among 37,105 women.
1085/37105= 0.02924/8 (yrs.)= 0.003655*100,000= 365.5 cases per 100,000 women (ask for help???)

Question 14

Population risk?

Answer 14

the denominator for incidence rates; those members of a population who are at risk for contracting a specific disease or adverse health outcome

Question 15

Attack rate?

Answer 15

(AR) is an alternative for the incidence rate. Used when the nature of the disease is such that a population is observed for a short time period, often as a result of specific exposure
Ex: 87 people ate turkey for dinner and 63 became ill and the rest didn’t. What’s the AR?
AR= ill/ (ill+well)100; (ill/total)100
63/ (63+24)*100= 72.4%

Question 16

Cumulative incidence?

Answer 16

incidence expressed as a proportion of a cohort or group at risk; # of new cases of disease occurring over a time period in population at risk at beginning of interval

• the proportion of of at risk pop. who develop the disease
• estimates the risk of developing the disease

Question 17

Incidence density?

Answer 17

the average PERSON-TIME incidence rate; an incidence measure used when members stored in a pop. or study group are under observation for different lengths of time
-Subjects enter/exit the candidate pop. at varying times
-Recruited to study over time
Subjects are “lost to follow up”and don’t complete the study

Question 18

What’s the interrelationship between prevalence and incidence?

Answer 18

The prevalence of a disease (P) is proportional to the incidence rate (I) * the duration (D) of a disease

Question 19

What are crude rates?

Answer 19

Summary rates based on the actual # of events in a pop. over a given time period
Ex: Look at Exhibit 3-5 on pg. 310-311

Question 20

Crude birth rate?

Answer 20

# of live births during a specified period of time (1 yr.) per the resident pop. during the midpoint of the time period
Ex: 3,945,875 babies were born in the US in 2016 in the US when the pop. size was 323,127,513
3,945,875/323,127,513= 12.2 per 1000

Question 21

General fertility rate?

Answer 21

average # of children born in a time period. Expressed as 1000 women per age (whatever age given)

Question 22

Total fertility rate?

Answer 22

the average # of children that would be born per woman if all women lived to the end of their childbearing years and bore children according to a given set of age specific fertility rates

Question 23

Fetal mortality?

Answer 23

Spontaneous intrauterine death of the fetus at any time during the pregnancy

Question 24

Fetal death rate

Answer 24

of fetal deaths after 20 weeks gestation or more/# of live births plus fetal deaths (20 weeks gestation or more). Expressed as rate per 1,000 live births and fetal deaths

Question 25

Late fetal death rate?

Answer 25

fetal deaths after 28 weeks gestation or more

Question 26

Fetal death ratio?

Answer 26

(# of fetal deaths after gestation of 20 weeks or more/ # of live births during a yr.) * 1,000 live births

Question 27

Infant mortality death rate?

Answer 27

(# of infant deaths in a yr./# of live births in a yr.) * 1000 live births
Ex: there were 23,161 infant deaths and 3,945,875 live births in a year
(23,161/3,945,875)*1000= 5.87 per 1000 live births

Question 28

Neonatal mortality rate?

Answer 28

(# of infant deaths under 28 days of age/# of live births) * 1000 live births
-“neo” means new. When the baby is new to the world (aka newborn)

Question 29

Postneonatal mortality rate?

Answer 29

(# of infant deaths from 28-365 days after birth/# of live births) * 1000 live births

Question 30

Maternal mortality rate?

Answer 30

of maternal deaths ascribed to childbirth per 10,000 or 100,000 live births

Question 31

What are specific rates?

Answer 31

A type of rate based on a particular subgroup of the pop. defined
Ex: in terms of race, sex, or age

Question 32

Cause specific rate?

Answer 32

a rate that specifies events, such as deaths according to their cause
Ex: assault, chronic liver disease, environment, etc. 1

Question 33

Age specific rates?

Answer 33

a rate for a specific age group. The numerator and denominator apply to the same age group* 100,000

Question 34

Proportional mortality ratio?

Answer 34

the # of deaths w/in a pop. due to a specific disease or cause/total # of deaths in pop.

Question 35

Adjusted rates

Answer 35

summary measures of the rate of morbidity and mortality in a pop. which statistical procedures have been applied to remove the effect of differences in composition of the various pops.

Question 36

Direct method?

Answer 36

a rate adjustment that applies specific rates for a group to a standard pop.

Question 37

Direct v. Indirect Age Adjustments

Answer 37

• Direct is more common and indirect age adjustment should be used if direct is not possible
• Rates based on small #s of deaths will have a big amount of random variation
• Indirect standardization is generally thought of as an approx. to direct standardization