PU520: Principles of Epidemiology Unit 3 Descriptive Epidemiology/General Health and Population Indicators Flashcards
How does descriptive epidemiology describe data?
It describes it according to person, place, and time.
What is implicit in epidemiology?
The notion of public health surveillance.
Surveillance is a means of monitoring exposures, diseases, events, behaviors, and conditions.
For descriptive epidemiology…
Person addresses?
Place addresses?
Time addresses?
Who is getting the disease, disability, injury, or death.
Where the health-related states or events are occurring most or least frequently.
Addresses the range in which the disease manifested or when the event occurred related to the disease. This can be hours and weeks to years and decades.
When addressing the person in descriptive epidemiology, what are some descriptors you can use?
Descriptors often include age, gender, race/ethnicity, marital and family status, occupation, and education.
What is another word used to occasionally describe time factors in epidemiology?
Temporal
What is two ways an approach to control for the potential confounding effects of age over time in a study?
Restrict the study to age-specific categories
Report age-adjusted rates. (allows communities with different age structures to be compared)
What have been used for many years by demographers and epidemiologists to track and compare changes in population age distributions over time?
Population (or age) pyramid
What is a decennial census?
It is when age and sex characteristics of a population are collected at a specific point in time which usually happens in years ending in zero by the Census Bureau.
What does an expansive pyramid look like and what does it represent?
It has a broad base and a tall, pointed shape (looks like a Hershey’s kiss)
It represents a rapid rate of population growth and a low proportion of older people.
What does a stationary pyramid look like and what does it represent?
It is more block shaped and indicates low fertility and low mortality.
This represents a more industrialized society, with effective public health measures in place, good socioeconomic conditions, and good medical care; life expectancy is high, with large numbers of age cohorts living into the older age groups.
What does a constrictive pyramid look like and what does it represent?
it is a population pyramid showing a lower number or percentage of younger people.
The people are generally older, with a low death rate but a low birth rate as well. This type of pyramid is occurring more frequently, particularly in European countries.
What is a dependency ratio?
It reflects the amount of potential dependency in a population and the work life span.
It describes the relationship by age between those who have the potential to be self-supporting and the dependent segments of the population–in other words, those segments of the population not in the workforce.
What are the ratios that have been developed for specific occupations which were based on the risks that might be associated with the physical and chemical exposures common to said occupations?
Standard morbidity/mortality ratios (SMRs)
How do you calculate the dependency ratio?
It is the dependent population age groups < 15 years old and 65+ combined divided by the age of the workforce ages 15-64 x 100.
This can be used for percentages, too. Not just numbers of people.
(Exercise Question) 2020 Dependency Ratio for the United States
0 -14 = 60,590,323 pop
65+ = 54,828,523 pop
Working pop
15-64 = 216094666 pop
53.41% of the population is dependent on the working class in the U.S. (2020)
2020 Dependency Ratio for Afghanistan
0-14 = 14772317
65+ = 1004606
Working pop
15-64 = 20817853
75.79% of the population is dependent on the working class in Afghanistan
What are the five broad classifications of occupations?
- Unskilled
- Partly skilled
- Skilled
- Intermediate
- Professional
What is the term health worker effect mean?
It is a term used to describe an observation of working populations tending to have a lower mortality rate than the general population.
Workers tend to be a healthier group to begin with. Persons who are unhealthy or who may have a life-shortening condition are less likely to be employed. As workers go through the life span, the chance of death increases, and the healthy worker effect decreases. Unhealthy workers tend to leave the work environment or retire earlier than healthy employees. Leaving work early in life also reduces exposure to occupational hazards.
General Information
Age has a strong influence on the outcomes and findings of studies and it must be considered.
Health related states or events often differ between males and females.
Racial or ethnic variations in health-related states or events are explained primarily by exposure or vulnerability to behavioral, psycho-social, material, and environmental risk factors and resources. Historically, biological explanations have
played a limited role in explaining racial disparities.
Studies have related marital status and health for over a century. Married individuals have been shown to experience lower mortality than do unmarried individuals, regardless of whether the unmarried persons were never married, divorced, separated, or widowed.
Married persons in the United States have also been shown to generally have lower levels of physical, mental, or emotional problems and better health behaviors (more physically active, less smoking, less heavy alcohol drinking); however, married persons,
particularly men, were shown to have higher rates of excessive weight or obesity.
Studies have shown that family size and marital status can influence physical and mental health. In addition, health behaviors cluster in families. Parental attitudes and behaviors can directly influence their children’s health behaviors. person inherits many traits, both good and bad, from parents, grandparents, and past family members. Genetically, intelligence levels can be passed down from generation to generation, along with some diseases.
The personal characteristic of occupation can be reflective of income, social status, education, socioeconomic status, risk of injury, or health problems within a population group. Selected diseases, conditions, or disorders occur in certain occupations. Brown lung has been associated with workers in the garment industry, black lung with coal miners, and certain accidents and injuries to limbs with farm workers.
Education, like occupation, can be a valuable measure of socioeconomic status. Persons with training, skills, and education make substantially more money per year than persons with no training or skills. Persons with higher education levels are more prevention oriented, know more about health matters, and have greater access to health care.
Education has the largest impact on dental care, followed by prescription drugs and medical care.
For chronic conditions such as cancer, geographic comparisons of disease frequency among groups, states, and countries can be made to provide insights to the causes of diseases.
Time-series designs involve a sequence of measurements of some numerical quantity made at or during two or more successive periods of time. The simple time-series design involves the collection of quantitative observations made at regular intervals through repeated observations. Some examples include air temperature measured at noon each day, number of hospital admissions per day, number of deaths per day, and air pollution levels per day.
Time-series analysis may involve assessment of a group of people who have experienced an event at roughly the same time, such that these individuals may be thought of as a cohort. Time trend analysis of cohort data allows researchers to study the pattern of illness or injury for a group of people who experienced an exposure at roughly the same time.
What do you call a histogram (number of cases x time) where the duration time of the epidemic is reflected?
An epidemic curve!
These time intervals can really be any measurement of time that makes sense.
Why should you create sufficient lead period in a histogram before the suspected exposure and clinical manifestations of the disease?
To demonstrate the incubation period.
How is the shape of the epidemic curve in a histogram influenced?
It is influenced by whether the source of exposure is at a point in time or continuous over time.
In a point source epidemic, individuals are exposed to the same source over a limited time period. Because incubation or latency period influences the rate of increase and decrease in the epidemic curve, a point source epidemic tends to show a clustering of cases in time, with a sharp increase and a trailing decline.
Example of point source such as a single meal or event attended by all cases.
In a continuous source epidemic in which exposure is continuous over time but at relatively low levels, the epidemic curve tends to gradually increase, plateau, and then decrease. The rate of decrease depends on the latency period and whether the exposure is removed gradually or suddenly.
Example is the cholera epidemic in Broad Street area of London, England in 1854.
What refers to the same sample of respondents being observed over time?
Longitudinal data
Use of longitudinal data avoids some of the concern regarding confounding in ecologic studies. Factors that change little over time do not confound time-series studies, but confounding could occur from time-varying environmental factors (e.g., secular trend, carryover effect, residual influence of the intervention on the outcome).
What are the three potential effects that are generally considered when investigating patterns in time-series data?
The age effect is the change in rate of a condition according to age. This effect is irrespective of birth cohort or calendar time.
A cohort effect is the change in the rate of a condition according to birth year. This effect is irrespective of age and calendar time.
A period effect is a change in the rate of a condition affecting an entire population at a given point in time. This effect is irrespective of age and birth cohort.
Environmental factors contribute to both cohort and period effects. When researchers observe cohort or period effects, this can help in the investigation to determine the causes of health-related states or events.
What involves a shift or change in the trends in rates that affect all birth cohorts and age groups?
A period effect.
Period effects are responses to phenomena that occur at a period of time across the entire population. A period effect may result from the introduction of a new antibiotic, vaccine, or disease-prevention program that affects various age groups and birth cohorts in a similar manner.
A period effect may also result from adverse physical stresses or social conditions (e.g., earthquake, flood, terrorism, war, economic collapse) that affect the entire population irrespective of age group or birth cohort.
What involves a sequence of measurements of some numerical quantity made at or during two or more successive periods of time?
Time-series design
What are the two ways time-series designs can be described?
Secular trend and seasonality.
What is the general systematic linear or nonlinear component that changes over time in a time-series design?
Secular trend.
It represents the long-term changes in health-related states or events. In the epidemiology literature, another term, temporal variation or trends (also called temporal distribution), has emerged and is being used interchangeably with secular trends.
Increasing changes seen over extended time periods, even several decades in certain diseases, are of concern in epidemiology, especially in terms of prevention and control. Secular trends are usually considered to last longer than 1 year.
Describe a short-term trend or fluctuation.
It usually reflects a brief, unexpected increase in a health-related state or event. Short-term trends occur over small time intervals or limited time frames.
Even though seasonal and cyclic trends occur within short time frames, because of their unique features, they are used as separate categories.
Most short-term trends are limited to hours, days, weeks, and months. Thus, events of limited duration are included in the short-term trends category. An example of a short-term time frame would be the cholera epidemic studied by John Snow in the mid-1800s.
What represents periodic increases and decreases in the occurrence of health-related states and events?
Cyclic patterns.
These patterns are often predictable.
Some disease cycles are seasonal, whereas cycles of other diseases may be controlled by other cyclic factors such as the school calendar, immigration patterns, migration patterns, duration and course of diseases, placement of military troops, and wars.
Other phrases used to describe trends of disease cycles are secular and seasonal cyclical patterns. Cyclic changes refer to recurrent alterations in the occurrence, interval, or frequency of diseases. Some disease outbreaks occur only at certain times but in predictable time frames or intervals over long terms; thus, epidemiologists track cyclic changes over time.
Chickenpox is one of the notifiable diseases and is more easily and accurately tracked than others. The cyclic nature of chickenpox (most common in the winter and spring)
Cyclical disease patterns have also been associated with extreme temperatures, seasonal patterns in diet, physical activity, and environmental factors (e.g., agricultural pesticides).
For example, evaluation of daily deaths in England and Wales and in New York has found a relationship between temperature and deaths from myocardial infarction, stroke, and pneumonia. Death rates rise with extreme cold and hot temperatures. The influence of temperature on deaths is much stronger in the elderly.
What represents periodic increases and decreases in the occurrence, interval, or frequency of disease?
Seasonal trend.
These patterns tend to be predictable.
Some disease cycles are seasonal, whereas other disease cycles may be influenced by cyclic factors such as the school calendar, immigration pat-terns, migration patterns, duration and course of dis-eases, placement of military troops, wars, famine, and popular tastes in food.
Certain pathogen-borne diseases have a seasonal pattern that corresponds with changes in the vector populations, which in turn are influenced by environments where the vectors live and multiply. For example, in 2005, the nationally reported West Nile virus cases began late in May, peaked in the third week of August, and then lasted through November.
What refers to the number of years an individual is likely to live?
What does “life expectancy at birth” mean?
Life expectancy
It is just the average number of years a newborn is likely to live, assuming that the mortality rates at the time of birth remain constant over the infant’s lifetime.
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