8 Mortality + Morbidity Stats. Flashcards
Why do classifications of disease change over time
- Recognition of new diseases
- Changes in classification
leading cause of death male vs. female
- Coronary heart disease (male)
- Dementia (female)
CRUDE death rates
BASED on actual number of events
* often not useful
Crude Annual Death Rate
Total number of deaths in a 12-month period
Why do we need to use specific death rates as opposed to crude?
Need to look at specififc death rates and population composition SEPERATLEY
Specific Death Rates
Measure mortality for a specific group in a population
* usually consider 1 factor (e.g. age)
Confounding Factors
distortion of a measure of the effect of an exposure on an outcome due to the association of the exposure with other factors influencing the outcome
Age Adjustment or Standardisation
Adjusting rates for differences in population age structure
* Attempt to remove age as a confounding factor
* Create ‘dummy‘ age composition
* Re-calculate overall rates
Why are Adjusted (standardised) Rates
more efficient.
Remove the need for comparison of each stratum (of characteristic) within pop. at one time
What is used to standardise rates?
A fictitious pop. or rate matrix
* Get age specific death rate from each age group > multiply by number for overall pop.
Direct Standardisation
- Age-specific rate in YOUR population(s)
- Age-distribution in “standard” population
Indirect Standardisation
- Age distribution in YOUR population
- Age-specific rate in “standard” population
Sources of morbidity stats.
- Insurance companies
- Gov.
- Armed Forces
Types of Data Collected
(Morb. Stats.)
- Screening (high vol, low qual.)
- Hospital Records
- Long-term reg. (low vol, high qual).
Screening
Tests on “well” people
* reduce morb. > prevent progression
* need confirmatory tests
Interview Data
Greatest problem is under-reporting
* Worse if hearsay
Permanent Long-Term Registration
Best data
* Costly
* Compliance?
* e.g. cancer registry
Cancer Incidence by Sex
Prostate 1# for males
Breast 1# for females
Migration and cancer incidence
Rates of certain cancers in migrated populations would increase and match local rates
* enviro factors in each place
How to assess validity of a test
- SENSITIVITY of the test (True Pos/All with disease)
- SPECIFICITY of test (True Neg/All with disease)
Continuous Variable (biomarker): IDEAL Case
There would be minimal cross over between healthy and diseased based on serum levels
Continuous Variable (biomarker): REALITY
There is some cross over
* False neg + pos
* need to choose a lower threshold of serum > fewer false neg
SENSITIVITY
a/(a + b) = True POS rate
refer to table in doc
