04 Measure of mortality edited 21 Jul 2022.pptx

Measure of mortality edited 21 Jul 2022

1. Measure of mortality Soo Kuan Meng Lecture 4 (28 Jul 2022) 1

2. Learning outcomes Calculate the mortality rates, case fatality, proportionate mortality, years of potential life lost by using formula. State the uses and disadvantages of different measure of mortality. Explain the possible reasons of increased mortality. Carry out direct and indirect age adjustment. Discuss the other measure of impact of disease. 2

3. Formula of mortality 1) Number of death 2) Mortality rates = total no. of death in 1 year x 100,000 No. of person in the population at midyear Eg Population size = 100,000 No of death due to disease x = 18 Mortality = 0.018% Note: Number of persons at midyear is used because population changes over time. 1 year is arbitrary. It can be 5 years or longer. 3

4. Formula of mortality Mortality rate from black and white individuals have gone down from 1980 to 2014. 4

5. Formula of mortality 3) Case fatality = no. of individuals dying x 100% No. of individuals with the specified disease Eg No. of patient = 20 No. of death = 18 Thus, case fatality = 90% Note: unlike mortality rates, the denominator are those who have the disease 4) Proportionate mortality = no. of deaths from certain disease in US in 2015 x 100 Total deaths in US in 2015 Eg No. of death = 30 No. of death due to heart disease = 3 Proportionate mortality = 10% 5

6. Formula of mortality Proportionate mortality. Major causes of death in children under 5 years in 2015. Leading cause of death among children younger than 5 years were preterm birth complications, diarrhea and congenital abnormalities. Neonatal death accounted for 45% of deaths under 5 years. 6

7. Formula of mortality 5) Years of potential life lost Sum of years of potential life loss Where years of potential life loss = average age at death - person’s age death Eg Age of a person death = 1 Predetermined age = 75 Thus YPLL = 74 7

8. The uses and disadvantages of measure of mortality 1) Number of death Rate 2) Mortality rates Measure risk of disease. Suitable for acute and fatal disease eg untreated rabies and pancreatic cancer. Do not measure risk because do not have denominators. Deaths increases could be due to population increases and not risk increases. Not suitable for mild and not fatal disease with long duration. 8

9. Formula of mortality Trend in observed numbers of cancer deaths for men and women in the United States 1969-2014. Increase number of death does not mean risk of dying increases because if the size of populations is also increasing, the risk of dying does not change. 9

10. Formula of mortality Mortality rates for cancers of the liver, lung and bronchus, uterus and colon and rectum for males, United States, 1930-2014. Mortality rates are affected by these coding changes. Lung cancer declines parallel with decreases in rates of smoking among men. Stomach cancer declines may be due to increased availability of refrigeration, which decreases smoked food, a carcinogen. The declines also could be due to improved hygiene which reduces helicobacter pylori infections which causes stomach cancer. 10

11. Formula of mortality Mortality rates for cancers of the liver, lung and bronchus, uterus and colon and rectum for females, United States, 1930-2014. Mortality rates are affected by these coding changes. Uterus cancer declines maybe due to earlier detection and diagnosis. 11

12. Formula of mortality Mortality rates from cancer and heart disease for ages younger than 65 and 65 or older. Cancer is leading cause of death in those younger than 65 years. Heart disease exceeds cancer as cause of death for those above 65 years. 12

13. Formula of mortality Mortality for those aged 45-64 declines. This may be due to early detection of cardiovascular diseases and cancers and effective treatment. Mortality for those aged 25-44 increases in 1980. this may be due to emerge of HIV disease. Mortality rate declines sharply in 1990s. This may be due to antiretroviral therapy and public health education. 13

14. The uses and disadvantages of measure of mortality Proportion 3) Case fatality Measure severity of disease or benefit of therapy in reducing severity of disease. 4) Proportionate mortality Measure major cause of death Cannot differentiate deaths from the disease and deaths from other causes. Eg alcoholic person die in a car accident could be due to other reasons Do not measure risk. Increased proportionate mortality could be due to decreased proportionate mortality of other diseases and not increased risk of death from the disease. 14

15. Formula of mortality Proportionate mortality. Deaths from heart disease as a percentage of deaths from all causes, by age group, United States, 2014. Proportionate mortality from heart disease increases with age, does not mean that risk of death increases with age. 15

16. Formula of mortality Proportionate mortality of heart disease in community A is lower than community B, does not mean that risk of community A is lower, because the mortality rate are the same 16

17. Formula of mortality Proportionate mortality from cancer and other causes decrease in later period, does not mean that risk decreases but because proportionate mortality from heart disease increases. Mortality rate from cancer and other causes remain the same. 17

18. Formula of mortality Proportionate mortality from cancer and other causes decrease in later period, does not mean that risk decreases but because proportionate mortality from heart disease increases. Mortality rate from cancer and other causes remain the same. 18

19. Formula of mortality Proportionate mortality remain the same does not mean risk remain the same. The mortality rate decreases. 19

20. Formula of mortality Understanding proportionate mortality 20

21. Formula of mortality Proportionate mortality from communicable and noncommunicable causes in developing countries, 1990 and projected into 2020 (Harvard University Press on behalf of WHO and world bank, 1996) Non communicable disease has high proportionate mortality because of aging of population worldwide and advances in economic development. Communicable diseases are expected to decrease. 21

22. The uses and disadvantages of measure of mortality 5) Years of potential life lost Measure death occurring at younger age, because death occurring at younger age involves a greater loss of YPLL than at older age. This helps to establishing research resource priorities. 22

23. The uses and disadvantages of measure of mortality YPLL. In US the greatest single source of YPLL was malignant neoplasms. Unintentional injury has second highest YPLL. 23

24. The uses and disadvantages of measure of mortality YPLL. YPLL from motor vehicle accidents accounts for over half of YPLL. Thus we should address the specific cause of injury related to motor vehicles. 24

25. The uses and disadvantages of measure of mortality YPLL. Suicide is ranked fourth by YPLL. This means a large proportion of suicide occur in young persons. 25

26. Condition where mortality can approximate the risk of disease When the disease being studied is a severe and lethal one (high case fatality), mortality rates may serve as surrogates for incidence rates, hence mortality can approximate the risk of disease. 26

27. Interpreting the results Increased in mortality could be due to: 1) True decrease in survivorship 2) Changes in coding rules/ classification. Eg changes in international classification of disease (ICD) from seventh revision to eighth revision causes declines in death due to diabetes. This is because seventh revision stated that any death certificate that mention of diabetes anywhere be coded as a death from diabetes; whereas eighth revision stated that only when underlying cause of death was listed as diabetes were coded as a death from diabetes. 3) Changes in age composition. When there were more people in oldest age group and overall mortality is weighted by the higher rates in older age group. Adjustments are done to hold constant the age composition, to prevent difference in age composition from affecting the results. 27

28. issues that arise in comparing mortality across two or more populations When comparing populations, such populations may differ with regard to many characteristics that affect mortality, of which the age distribution is the most important. Adjustments are done to hold constant the age composition, to prevent difference in age composition from affecting the results. 28

29. Interpreting the results US standard certificate of death. 29

30. Interpreting the results Cause of death section on a death certificate, including immediate cause and underlying causes and other significant conditions. 30

31. Interpreting the results Mortality rates for diabetes for those aged 55- 64 drops. This is due to changes in international classification of diseases coding. In which, the seventh revision stated that any death certificate that mention of diabetes anywhere be coded as a death from diabetes; whereas eighth revision stated that only when underlying cause of death was listed as diabetes were coded as a death from diabetes. 31

32. Interpreting the results AIDS cases, United States, 1984-2000. AIDS cases rises in 1993. this is because in 1993, a new definition of AIDS was introduced. More cases meet the diagnostic criteria for the disease. 32

33. Interpreting the results Mortality rate is higher in whites than in blacks. However, mortality in each age specific group is higher in blacks than in whites. This is because white is older than the black and the overall mortality is heavily weighted by high rates in oldest age groups. 33

34. Direct and indirect age adjustment Direct age adjustment Create a standard population by sum up age specific population of both groups. Calculate the expected no. of death by applying specific mortality rates to the standard population. Calculate the expected total number of deaths/ the age adjusted rates Thus, we know whether there is any difference in mortality, when the age compositions are the same Indirect age adjustment Used when deaths of each age specific stratum are not available Calculate the no. of death by applying the age specific rate of a known population to each age group in the population of interest. Calculate the expected total number Calculate the standardized mortality ratio (SMR) = total number of deaths observed Total number of deaths expected 34

35. Interpreting the results The mortality rate is higher in later period than early period. However, the age specific data for the latest period is lower in each group. This is because the oldest group increases in later period and mortality is highest in the oldest age groups. 35

36. Interpreting the results To know if age composition affects the difference in mortality, we need to do age adjustment. Direct age adjustment. Create a standard population by sum up age specific population of both groups. Calculate the expected no. of death by applying specific mortality rates to the standard population. Calculate the expected total number of deaths/ the age adjusted rates Results show that age composition affects the difference in mortality. 36

37. Interpreting the results Indirect age adjustment. Calculate the no. of death by applying the age specific rate of a known population to each age group in the population of interest. Calculate the expected total number Calculate the standardized mortality ratio (SMR) = total number of deaths observed Total number of deaths expected Thus, the number of deaths exceeds the expected number. 37

38. Others measures of impact of disease Quality of life Different in different patients based on personalities, preference etc. Such as physical and emotional suffering, disability Eg patients with arthritis are compromised by illness in carrying out daily activities 38

39. Others measures of impact of disease Disability adjusted life year (DALY) of selected of disease by low and high income countries. Disability adjusted life year is the number of years of life lost to premature death or live with disability. Ischemic heart disease and respiratory tract infections are causing high DALY in high income and low income countries respectively. 39