- Mortality
-
Mortality is the number of deaths occurring in a given period in a specified
population. It can be expressed as an absolute number of deaths per year or as
a rate per 100,000 persons per year.
- Population at risk
-
The population at risk includes all individuals susceptible to a specific
cancer. It is defined on the basis of demographic variables, such as place of
residence, sex, age group. Years of risk duration are counted in person-years.
- Age-specific rate
-
The age-specific rate is calculated simply by dividing the number
of cancer deaths observed in a given age category during a given time
period by the corresponding number of person years in the population at risk in
the same age category and time period. For cancer, the result is usually
expressed as an annual rate per 100,000 person-years.
- Crude rate
-
Data on mortality are often presented as rates. For a specific tumour and
population, a crude rate is calculated simply by dividing the number of cancer
deaths observed during a given time period by the corresponding number of
person years in the population at risk. For cancer, the result is usually
expressed as an annual rate per 100,000 persons at risk.
- ASR (age-standardised rate)
-
An age-standardised rate (ASR) is a summary measure of the rate that a
population would have if it had a standard age structure. Standardization is
necessary when comparing several populations that differ with respect to age
because age has a powerful influence on the risk of dying from cancer. The ASR
is a weighted mean of the age-specific rates; the weights are taken from
population distribution of the standard population. The most frequently
used standard population is the World Standard Population. The
calculated mortality rate is then called age-standardised mortality rate
(world). The world standard population used within the application is as
proposed by Segi (1960) and modified by Doll and al. (1966). The ASR is also
expressed per 100,000.
-
| Age distribution of the world standard population |
| Age group |
wi |
| 0-4 |
12000 |
| 5-9 |
10000 |
| 10-14 |
9000 |
| 15-19 |
9000 |
| 20-24 |
8000 |
| 25-29 |
8000 |
| 30-34 |
6000 |
| 35-39 |
6000 |
| 40-44 |
6000 |
| 45-49 |
6000 |
| 50-54 |
5000 |
| 55-59 |
4000 |
| 60-64 |
4000 |
| 65-69 |
3000 |
| 70-74 |
2000 |
| 75-79 |
1000 |
| 80-84 |
500 |
| 85+ |
500 |
| Total |
100000 |
- Cumulative risk
-
Cumulative mortality is the probability or risk of individuals dying
from the disease during a specified period. For cancer, it is expressed as
the number of new born children (out of 100, or 1000) who would be expected to
die from a particular cancer before the age of 75 or (80 or
85) if they had the rates of cancer observed in the period in the absence
of competing causes. Like the age standardised rate, it permits comparisons
between populations of different age structures.
- Standard error
-
The standard error of a rate is a measure of the sampling variability of the
rate.
- Confidence interval
-
A range of values that has a specified probability of containing the unknown
true rate or trend. The 95% (p-value = .05) and 99% (p-value = .01)
confidence intervals are the most commonly used.
- Annual percentage change (APC)
-
The annual percentage change is used to describe the magnitude of change in the
trend on fitting a simple regression model to the log of the ASR. It is the average
annual rate of change in the ASR over the time period selected.
|
GLOSSARY OF TERMS