1. دکتر حسین صافی زاده بهمن 1389 دکتر حسین صافی زاده بهمن 1389 منبع :درسنامه طب پیشگیری و پزشکی اجتماعی پارک جلد اول ،فصل اول بسم الله الرحمن الرحیم اندازه گیری در اپیدمیولوژی Epidemiologic Measures

2. اهداف درس انتظار می رود شما با مطالعه این درس:  اصطلاحات نسبت، تناسب و میزان را توضیح دهد.  مفهوم صورت و مخرج کسر را در مورد میزان توضیح دهد.  اندازه گیری های مربوط به مرگ و میر را توضیح دهد.  اندازه گیری های مربوط به مرگ و میر را محاسبه نماید.  اندازه گیری های مربوط به ابتلا را توضیح دهد.  رابطه بین بروز و شیوع را توضیح دهد.  اندازه گیری های مربوط به ابتلا را محاسبه نماید.

3. Epidemiologic Measures اندازه گیری میزان مرگ و میر (Mortality) اندازه گیری ابتلا به بیماری ها (Morbidity) اندازه گیری معلولیت و ناتوانی (Disability & Handicap) اندازه گیری موالید (Birth) اندازه گیری حضور، فقدان و یا چگونگی توزیع خصوصیات یا صفات مربوط به بیماری ها اندازه گیری نیازهای پزشکی، تسهیلات بهداشتی، استفاده از خدمات بهداشتی اندازه گیری، حضور، فقدان و یا توزیع عوامل محیطی و یا سایر عواملی که ممکن است نقش علیتی برای ایجاد بیماری داشته باشند. اندازه گیری متغیرهای جمعیتی

4. فرض کنید در یک مدرسه شبانه روزی 10 دانش آموز دچار آنفلوانزا شده باشند. به نظر شما وسعت مشکل دراین مدرسه چقدر می باشد؟ N = 50 آیا دانستن تعداد بیماران به تنهایی کافی می باشد؟ برای درک بهتر حجم مشکل، به چه اطلاعاتی نیاز می باشد؟

5. N = 240

6. N = 50

7. Epidemiologic Measures نسبت (Ratio) تناسب (Proportion) میزان (Rate)

8. Ratio نسبت Used to compare two quantities Examples: Ratio of male to female birth

9. Ratio نسبت Examples: Ratio of physician to population

10. Ratio نسبت Examples: Ratio of WBC to RBC

11. از ابزارهای اندازه گیری فراوانی بیماری ها می باشد. صورت کسر، بخشی از مخرج کسر نیست. صورت و مخرج کسر ممکن است، فاصله زمانی داشته و یا هر دو لحظه ای بیان شوند. Ratio نسبت

12. Proportion تناسب

14. A specific type of ratio in which the numerator is included in the denominator Usually presented as a percentage

15. Proportion تناسب Tell us what fraction of population is affected

16. Proportion تناسب Example: Male undergoing bypass surgery at hospital A Total patients undergoing bypass surgery at hospital A × 100

17. Rate میزان 1388 1389

18. Rate میزان Special form of proportion that includes a specification of time Most commonly used in epidemiology because it most clearly expresses probability or risk of disease or other events in a defined population over a specified period of time

19. Rate میزان Special form of proportion that includes a specification of time Most commonly used in epidemiology because it most clearly expresses probability or risk of disease or other events in a defined population over a specified period of time

20. Rate میزان 1388 Defined Population 1389 Specified period of time Tell us how fast the disease is occurring in a population

21.  K is used to denote the units of population such as per 1000 or per 100,000 Number of events in a specified time period Population at risk of these events in a specified time period × K× K Rate میزان 3200 deaths in kerman in 1388 800,000 Population in kerman in 1388 × 1000 = 4 per 1000

22. Numerator & Denominator Numerator is number of events that occurred in a defined population over a specified period of time Denominator  Population Population at midyear Population at risk Person-time Person-distance Subgroups in population  Events

23. Epidemiologic Measures Measurement of Mortality Measurement of Morbidity

24.  Crude death rate Total no. of deaths from all causes in 1 year No. of persons in the population at midyear × 1000 Measurement of Mortality

25.  Crude death rate Total no. of deaths from all causes in 1 year No. of persons in the population at midyear × 1000 Measurement of Mortality Example : 3200 deaths in 800,000 Population CDR= 3200/800,000 × 1000 = 4 per 1000

26.  Specific mortality rates  Age-specific mortality rate No. of deaths from all causes in 1 year in children younger than 5 years No. of children in the population younger than 5 years × 1000 Measurement of Mortality

27.  Specific mortality rates  Age-specific mortality rate No. of deaths from all causes in 1 year in children younger than 5 years No. of children in the population younger than 5 years × 1000 Measurement of Mortality

28. No. of deaths from lung cancer in 1 year No. of persons in the population at midyear × 1000 Measurement of Mortality  Specific mortality rates  Cause (disease) –specific mortality rate

29. Measurement of Mortality No. of deaths from leukemia in 1 year in children younger than 10 years No. of children in the population children younger than 10 years × 1000  Specific mortality rates  Age-specific mortality rate  Cause (disease) –specific mortality rate

30. Measurement of Mortality Example : Population A CDR= 15.2 per 1000 Population B CDR= 9.9 per 1000 What population have better condition?

31. > 6545 - 648 - 445 - 71 - 4< 1CDR 59.710.71.50.40.613.515.2A 61.118.83.60.5122.69.9B Measurement of Mortality Age – specific mortality rate in 1000 persons

32.  Case – fatality rate No. of individuals dying during a specified period of time after disease onset or diagnosis No. of individuals with the specified disease × 100 Measurement of Mortality  Proportionate mortality Rate - Of all deaths, what proportion were due to disease “ X ” No. of deaths from IHD in the kerman in 1388 Total deaths in the kerman in 1388 × 100

33.  Survival rate -Five – years survival : The percent of patients who are alive 5 years after treatment begins or 5 years after diagnosis Measurement of Mortality

34. Measurement of Morbidity 1388 1389 New case Incidence

35. Incidence بروز  The number of new cases of disease that occur during a specified period of time in a population at risk for developing the disease  Measure of the probability that unaffected persons will develop the disease Steps: identify a population that is free of the disease follow the population over time Observe person-time record new cases of disease as they occur

36. Incidence بروز Formula: No. of new cases of a disease occurring in the population during a specified period of time No. of persons at risk of developing the disease During that period of time × 1000 Example: 70 new cases of breast cancer in a 5 years period 3000 women at risk × 1000 = 23 ( 23 Cases per 1000 women during 5 years )

37. Measurement of Morbidity 1388 Prevalence

38. Prevalence شیوع  The number of affected persons present in the population at a specific time divided by the number of persons in the population at that time  Provides estimate of the probability or risk at one will be ill at a point in the time  Provides an idea of how severe a problem may be  Useful for planning health services (facilities, staff)

39. Prevalence شیوع Formula: No. of cases of a disease present in the population at a specified time No. of persons in the population at that specified time × 1000 Example: 700 cases of HTN in 1388 300,000 × 1000 = 2.3 ( 2.3 Cases per 1000 persons )

40. Prevalence شیوع Type of Prevalence : 1)Point prevalence  Prevalence of disease at a point in time  Number of cases that exist at a given point in time 2)Period prevalence  Number of cases that exist in a population at any time during a certain period

41. Prevalence & Incidence  Prevalence varies directly with:  Incidence  Duration of disease  If incidence is low, but duration is long (chronic); Prevalence will be large in relation to incidence  If prevalence is low because of short duration (due to recovery or death); Prevalence will be small in relation to incidence Prevalence = Incidence × Duration

42. Prevalence = Incidence X Duration P = I X D Prevalence Vs. Incidence

44. Exercise 1388 ? Prevalence

45. 1388 1389 ? Incidence Exercise

46. خسته نباشید! موج نهم ـــ اثر: ایوان آیوازوفسکی 1850 ـــ محل نگهداری: موزه دولتی روسیه، سن پترزبورگ