1. Standardization Prof Iain Crombie

2. Crude mortality rate Total no. of deaths Total population for specific time period 60,281 deaths * 1,000 5,120,000 population in Scotland in 1999 Crude mortality rate 11.8 per 1,000

4. Crude mortality rates Crude mortality rate depends on the age / sex structure of the population A country with a higher proportion of old people will have a higher number of deaths and a higher crude mortality rate

5. 0-14 years: Scotland: 15% Kazakhstan: 28% Costa Rica: 34% 65+ years: Scotland: 13% Kazakhstan: 7% Costa Rica: 5%

7. Mortality in New Zealand Maori490 Non-Maoris762 All cause mortality per 100,000

8. Age specific mortality rates

9. Comparing pyramids Crude mortality heavily influenced by age distribution

10. Solution: direct standardisation Take the age specific rates from population of interest Apply them to a standard population Calculate the new death rate if the age specific rates had occurred in the standard population Obtain an age standardised rate which adjusts for the effect of age

11. The new world standard population

12. A simplified calculation: Maori mortality rates Standard population (1) Age specific death rates per 100,000 (2) Expected deaths (3)= (1) x (2) / 100000 0-4886025822.86 5-1417290305.19 15- 241669012020.03 25-442928022164.71 45 – 64196801324260.56 65 +82006424529.02 100,000902.37 eg 0-4 yrs: 8860 x (258/100,000) = 22.86 eg 65+ yrs: 8200 x 0.06424 = 529.2 Age standardised rate = 902.37 per 100,000

13. Alternative calculation: if death rates low eg epilepsy Standard population (1) Age specific death rates per 100,000 (2) Expected deaths (3)= (1) x (2)* 0-488600.00 5-14172900.712,103 15- 2416690 0.9 15,021 25-44292802.573,200 45 – 64196803.874,784 65 +82003.125,420 100,000203,528 do not divide by100,000 until the end Age standardised rate = 203528 ÷ 100,000 = 2.04

14. Summary of direct standardisation  select standard population  no. of people in each age group  obtain age specific death rates

15. Comparing CrudeAge standardised Maori490902 Non-Maori762502 Why does age adjustment increase Maori rates and decrease Non-Maori rates?

16. Types of standard population  world  European  national  US  Australia

17. All Cancers Excluding Non-Melanoma Skin Cancer Countries of the UK, 2009 EnglandWalesScotlandN. Ireland Crude rateMen528623567485 Women495562571462 Age standardised Men424450452451 Women367386407387

19. Indirect standardisation: studying sub-groups Among doctors 14 cirrhosis deaths observed in 1970 – 14/43570 = 32 per 100,000 per year How does this compare to the UK average Too few to calculate reliable age specific rates Need another method – indirect standardisation – calculate Standardised Mortality Ratio – SMR – apply national age specific rates to the total group of doctors

20. SMR = O / E * 100 The basis of the SMR calculation  Calculate the expected deaths  if the national age specific rates  had occurred in the local population  Compare observed (O) with expected deaths (E)

21. Indirect standardisation: Farmers and mortality Death rate per 100,000 (1) No. of farmers (2) Expected deaths (1) x (2) / 100000 20-24138.3798011 25-34159.437,03059 35-44286.860,838174 45–54821.268,687564 55-642295.355,5651275 2083

22. Standardized Mortality Ratio Observed deaths = 1464 Expected deaths = 2083 O/E = 1464/2083 = 0.703 Standardized Mortality Ratio (O / E x 100) = 70.3 SMR = 70.3

23. Indirect standardisation: doctors and cirrhosis, 1921 E&W cirrhosis mortality Per 1,000,000 No. of doctors (2) Expected deaths (1) x (2) / 1,000,000 15-245.85910800.006328 25-3413.050128600.167823 35-4446.937115100.540245 45-54161.503103301.668326 55-64271.35877902.113879 4.4966004 If observed deaths = 14 O / E = 14 / 4.497 = 3.11 SMR = 311 %

24. SMRs for alcohol-related mortality, 2001 OccupationSMR Bar staff401 Window cleaners235 Chefs, cooks226 Hairdressers200 Painters and decorators171 Heavy goods vehicle drivers67 Van drivers54 Doctors27 Clergy25 IT managers22

25. SMR for Cirrhosis mortality by Social Class YearIIIIIINIIIMIVV 1991677511597119142 1921158183666986 What do the data show?

26. What you should know about standardization  adjusts for differences in population structure  commonly adjust for age distribution  separately by gender  can adjust for other factors  types of populations that may differ in age structure  developing and developed countries  one country at two time periods  occupational groups  social class  two methods  direct – age standardized rate  indirect – SMR small populations – eg regions, occupational groups