The total annual deaths in Florida and Alaska are 131,902 and 2,116, respectively. The total population in Florida is 12,340,000, and Alaska’s is 530,000. How are death rates compared?
Crude mortality rate
The simplest thing to do here is to calculate the crude mortality rates by dividing the deaths by the population.
| Florida | Alaska | |
| Crude mortality rate /100,000 | 131,902 x 100,000/12,340,000 = 1069 | 2,116 x 100,000/530,000 =399 |
The crude mortality ratio is 1069/399 = 2.68. Does that mean that the death rate is unusually high in Alaska?
Standardisation
The problem statement is: Do Alaskans (study population) have a higher mortality rate than the Floridians (standard population)?
Step 1: Mortality rate in the standard population – stratification by age group:
| Age | Population | Rate /100,000 |
| <5 | 850,000 | 284 |
| 5-19 | 2,280,000 | 57 |
| 20-44 | 4,410,000 | 198 |
| 45-64 | 2,600,000 | 815 |
| >65 | 2,200,000 | 4425 |
| Totals | 12,340,000 |
Step 2: Use study population age distribution to find the expected rate
| Age | Rate in Florida | Population Alaska | Expected deaths |
| <5 | 284 | 60,000 | 284×60,000/100,000 = 170.4 |
| 5-19 | 57 | 130,000 | 57×130,000/100,000 = 74.1 |
| 20-44 | 198 | 240,000 | 198×240,000/100,000 = 475.2 |
| 45-64 | 815 | 80,000 | 815×80,000/100,000 =65.2 |
| >65 | 4425 | 20,000 | 4425×20,000/100,000 = 89 |
| Total | 2256.7 |
Step 3: Compare total expected deaths to actual deaths
Standardised Mortality Rate (SMR) = 2,256.7/2,116 = 1.07
SMR is close to 1; therefore, there is nothing unusual about the death rate in Alaska compared to Florida.
References
Confounding and Effect Measure Modification: BUMC
