Chapter 3: Measures of Morbidity & Mortality Used in Epidemiology Flashcards
What is a count?
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
Ratio? Types?
A value obtained by diving the 1 quantity by another
- Simple-sex
- Demographic
- Sex ratio at birth
Proportions?
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%
Simple sex ratio
# 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)
Demographic sex ratio
SSR * 100
Ex: (151,781,326/156,964,212)* 100 = 96.7
Sex ratio at birth
SSR * 1000
Ex:
Rate? Elements?
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
Prevalence?
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
What is point prevalence?
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
What is period prevalence?
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
What is BMI?
Body mass index; a measure of obesity
Incidence?
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
Incidence rate?
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???)
Population risk?
the denominator for incidence rates; those members of a population who are at risk for contracting a specific disease or adverse health outcome
Attack rate?
(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%
Cumulative incidence?
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
Incidence density?
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
What’s the interrelationship between prevalence and incidence?
The prevalence of a disease (P) is proportional to the incidence rate (I) * the duration (D) of a disease
What are crude rates?
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
Crude birth rate?
# 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
General fertility rate?
average # of children born in a time period. Expressed as 1000 women per age (whatever age given)
Total fertility rate?
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
Fetal mortality?
Spontaneous intrauterine death of the fetus at any time during the pregnancy
Fetal death rate
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
Late fetal death rate?
fetal deaths after 28 weeks gestation or more
Fetal death ratio?
(# of fetal deaths after gestation of 20 weeks or more/ # of live births during a yr.) * 1,000 live births
Infant mortality death rate?
(# 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
Neonatal mortality rate?
(# 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)
Postneonatal mortality rate?
(# of infant deaths from 28-365 days after birth/# of live births) * 1000 live births
Maternal mortality rate?
of maternal deaths ascribed to childbirth per 10,000 or 100,000 live births
What are specific rates?
A type of rate based on a particular subgroup of the pop. defined
Ex: in terms of race, sex, or age
Cause specific rate?
a rate that specifies events, such as deaths according to their cause
Ex: assault, chronic liver disease, environment, etc. 1
Age specific rates?
a rate for a specific age group. The numerator and denominator apply to the same age group* 100,000
Proportional mortality ratio?
the # of deaths w/in a pop. due to a specific disease or cause/total # of deaths in pop.
Adjusted rates
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.
Direct method?
a rate adjustment that applies specific rates for a group to a standard pop.
Direct v. Indirect Age Adjustments
- 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
