MPH 6011 - Lecture 6
Calculate age-adjusted rate
1) sum of all expected deaths/2000 US Standard population 2) the sum of rate weighted column
The all-cause mortality rates in Florida and Utah are compared using age-adjusted rates based on the age distribution of the 2019 Florida population. What is the standard population used in this example?
2019 Florida population
Expected deaths
= 2000 US standard x rate as decimal
Rate as decimal
= death count/midyr population
Standardized morbidity (or mortality) ratio (SMR)
= observed/expected from two studies using the same standard risks but different study population distributions are NOT comparable
Rate per 100K
= rate as decimal x 100,000
rate weighted
= relative frequency x rate per 100K
Passive surveillance
A system in which either available data on reportable diseases are used or reporting is mandated or requested with the responsibility for the reporting often falling on the health care provider or district health officer Identify outbreaks Inform and evaluate public health measures Monitor trends = most national surveillance
active surveillance
A system in which project staff (often state/local) make periodic field visits to health care facilities such as clinics and hospitals to identify new cases of a disease or death from the disease that have occurred Time and resource intensive May occur during outbreaks Ebola May occur for conditions not mandated to be reported or known to be extensively under-reported
Annual surveillance data from State A indicate a marked increase in reported cases of a mosquito-borne viral illness in 2017 compared to each of the previous 10 years. What could account for the observed increase in cases?
Change in surveillance technique such as moving from passive to active surveillance Change in case definition that leads to a spike in reporting An actual increase in viral illness (outbreak)
serial surveys
Cross-sectional surveys that are routinely conducted - Conducted over a short period of time (usually a few days or weeks or months) Relies on participant self-report Recall; social desirability bias Interviewer bias No single case definition
Surveillance data and data from nationally representative surveys of health that are conducted on an annual basis (e.g., NHANES) share the following characteristics EXCEPT.
Data are only collected on individuals who actually have the condition
SMR < 1
Fewer health-related states or events were observed than expected from the age-specific rates in the standard population
SMR = 1
Health-related states or events observed were the same as expected from the age-specific rates in the standard population
SMR >1
More health-related states or events were observed than expected from the age-specific rates in the standard population
indirect age-adjusted rate
Observed population applied to standard rates In situations where age-specific rates are unstable because of small numbers or some are simply missing, age adjustment is still possible using this Calculate the standardized morbidity (or mortality) ratio (SMR)
direct age-adjustment
Observed rates applied to a standard population Two ways to carry out direct adjustment 1) Multiply the age-specific standard population by the age-specific rates (as decimal) to get the expected number of cases for each age group, assuming they had the same age distribution as the standard population These expected counts are then summed and divided by the total standard population 2) Multiply the age-specific standard population weight by the age-specific rates (as per 100,000) to get the expected rate for each age group, assuming they had the same age distribution as the standard population These expected rates are then summed (do NOT divide by the total standard population)
Time
Range from hours to weeks, years to decades Another term used occasionally to describe time factors in epidemiology is temporal
Choice of standard population
Should be representative of populations compared US 2000 standard population European standard population WHO world population One of the study populations Sum of study populations Bottom line, be able to use population that is representative and justifiable.
Prior to 2017, hypertension was defined as systolic blood pressure of ≥140 mm Hg or diastolic blood pressure ≥90 mm Hg. Beginning in 2017, hypertension is now defined as systolic blood pressure of ≥130 mm Hg or diastolic blood pressure ≥80 mm Hg. Which of the following is true?
The US adult prevalence of hypertension in 2017 will be higher than in 2016
What is the goal of public health surveillance?
To keep the public aware of new diseases
A surveillance case definition is a set of uniform criteria that allows counting and classifying cases consistently across counties and states.
True
In comparing the 2016 age-adjusted death rates for women with breast cancer in North Carolina to women with breast cancer in California in 2016, the combined populations of North Carolina and California for 2010 can be used as the standard population.
True
Indirect standardization using the Standardized Mortality Ratio is commonly used to identify excess mortality in occupational cohorts because the age-specific mortality rates within occupational groups is usually unknown.
True
Health indicators
Vital records, surveillance, and serial surveys provide information on key health indicators, progress made, and trends
Place
addresses the "where" question These data often involve comparisons between or among geographic regions County State Country
Which of the following is NOT a characteristic that can be used to describe health events by person?
age, gender, race, smoking status, income
A surveillance report provides the proportion of North Carolina residents who were obese each year for the period 2000 to 2019, according to age category, race, and county of residence. This information has each of the following components of descriptive epidemiology except which of the following?
age-adjusted rates
standard population
an arbitrarily selected population Should be sufficiently large Should reflect one of the groups being compared
crude rate
an outcome is calculated without any restrictions, such as by age or sex, on who is counted in the numerator or denominator
Person
answers the "who" questions Descriptors often include Age Sex Race/ethnicity Marital and family status Occupation Education Behavioral characteristics (exercise, diet, use of drugs) Structural characteristics (poverty, access to care, built environment)
Sentinel surveillance
based on selected population (or clinic) samples chosen to represent the relevant experience of particular groups. Useful in dealing with sensitive issues (HIV) or for the early detection of infections (influence) May include enhanced or more detailed data or types of data (e.g. swabs for ILI). May include the use of animal sentinels to detect circulation of arboviruses
Why do age-adjusted rates need to be use when comparing rates across time and populations?
different populations have different age distributions
secular trends
represent long-term changes in health-related states or events
cyclic trends
represent periodic increases and decreases in the occurrence of health-related states or events; seasonal
surveillance
the ongoing systematic collection, analysis, interpretation, and dissemination o health data in a timely manner to those who need to know Identify outbreaks or other urgent health events Informs implementation of control measures Evaluates implemented public health measures Monitors progress towards key health indicators Identifies trends in health outcomes, indicators, and risks (environmental and behavioral) Suggest topics for future research only collects info on people who get the disease
Short-term trends
usually brief, unexpected increases in health-related states or events; epidemic
age-adjusted rates
weighted averages of age-specific rates, where the weights are from a 'standard population' hypothetical (not actual rates) used for comparison purposes only only relative to the other adjusted rate
