1. Presented at The 129th Annual Meeting of the American Public Health Association Atlanta, GA, October 21–25, 2001 Presented by Kristine R. Broglio Thomas J. Hoerger James P. Boyle Amanda A. Honeycutt Linda S. GeissTheodore J. Thompson Forecasts of Diabetes in the U.S.: Results from a Markov Model P.O. Box 12194 · 3040 Cornwallis Road · Research Triangle Park, NC 27709 Phone: 770-234-5014 · Fax: 770-234-5030 · honeycutt@rti.org · www.rti.org

2. 2 Background n In 1997, 10.3 million people in the U.S. were estimated to have diagnosed diabetes l 35% higher than the estimated number in 1992 n Diabetes prevalence is highest among the oldest age groups and among certain racial/ethnic minorities l Future changes in diabetes prevalence may be expected given projected changes in the size and age/racial composition of the U.S. population and life expectancies

3. 3 Study Objectives n Generate forecasts of diabetes prevalence and the number of people with diabetes through 2050 by age, sex, and race/ethnicity n Use a dynamic modeling approach to predict the number of people with diabetes in each year based on flows into and out of the diabetes “state”

4. 4 Overview of Previous Studies n Forecasts of the number in the U.S. with diabetes l Helms (1992) — 12 million in 2050 l King, Aubert, and Herman (KAH; 1998) — 22 million in 2025 (diagnosed and undiagnosed) l Boyle et al. (2001) — 29 million in 2050 n Limitations of previous studies l Assume constant prevalence (or linear trend) u Prevalence is not determined based on flows into (incidence) or out of (death rates) the diabetes state l Most do not account for prevalence differences across race/ethnicity (e.g., Helms and KAH) l Generate forecasts for age groups (e.g., 0 to 44 years), rather than individual ages

5. 5 Methods — The Markov Modeling Approach n Markov models are used to simulate the progression of individuals through mutually exclusive disease states n 3 states of the diabetes forecasting model: no diabetes, diabetes, and death n Age, race/ethnicity, and sex-specific subgroups transition between states in each 1-year cycle of model l age (0 to 100 years, plus 101+) l sex (male, female) l race/ethnicity (non-Hispanic White, non-Hispanic Black, Hispanic, and Other) n Total number of subgroups = 816

6. 6 Markov Model of Diabetes Disease States and Transition Probabilities

7. 7 Data for Model Inputs (I) n Base Year (1999) Diabetes Prevalence l Estimated using NHIS for 1980–1998 l Used to determine initial distribution of individuals across the Diabetes and No Diabetes states n 1999 Diabetes Incidence l Estimated using NHIS for 1984–1998 l Age-, race/ethnicity, and sex-specific incidence rates used to forecast the flows of individuals into the Diabetes state l Base model assumes no temporal changes in incidence

8. 8 Data for Model Inputs (II) n Baseline U.S. Population l Census Bureau — middle series of population projections l Used to determine initial distribution of individuals across Diabetes and No Diabetes states n Forecasts of the Number of Live Births l Census Bureau — forecasts of number of children under one year of age through 2050 l Added to No Diabetes state in each model cycle n Forecasts of Net Migration l Census Bureau — middle series of population projections through 2050 l Added to Diabetes and No Diabetes states based on age, sex, and race/ethnicity-specific 1999 prevalence

9. 9 Data for Model Inputs (III) n Forecasts of the U.S. Population Mortality Rate l Census Bureau — mortality rate projections through 2050 l Used to estimate Diabetes and No Diabetes mortality rates (in conjunction with 1999 prevalence and estimated relative risk of death from diabetes) n Estimates of the Relative Risk of Mortality from Diabetes l From Tierney et al. (2000)

10. 10 Results — Forecasts of the Number of People with Diabetes, 1999–2050

11. 11 Results — Forecasts of Diabetes Prevalence, 1999–2050

12. 12 Results — Forecasts of Diabetes Prevalence, by Race/Ethnicity, 1999–2050

13. 13 Results — Impact of Changes in Incidence/Relative Risk of Death from Diabetes, 1999–2050

14. 14 Interpreting Results (I) n Projected growth in the population would lead to forecasts of 15.8 M in 2050 v. baseline forecast of 35.5 M

15. 15 Interpreting Results (II) n Projected aging of the U.S. population + population growth would lead to 19.9 M with diabetes in 2050 as compared to baseline forecasts of 35.5 M

16. 16 Interpreting Results (III) n Projected changes in the racial composition + age composition + population growth would lead to 22.4 M with diabetes in 2050 v. baseline forecast of 35.5 M

17. 17 Interpreting Results (IV) n What accounts for the rest of the growth in the number with diabetes from 1999 to 2050? l Dynamic modeling approach u Prevalence is determined within the model — not assumed to remain constant over time l Projected mortality rates u Increases in life expectancy mean an increase in the number of people at risk of developing diabetes in the oldest — highest incidence — age groups

18. 18 Sensitivity Analyses n Impact of using age-, race/ethnicity-, and sex-specific incidence rates that are 20% lower than baseline rates: l Projected number with diabetes in 2050 is 29.4 million l 2050 forecasts are 2.7 times greater than the number with diabetes in 1999 n Impact of using age- and sex-specific relative risks of death from diabetes that are 20% higher than baseline rates: l Projected number with diabetes in 2050 is 33.99 million l 2050 forecasts are more than 3 times higher than the number with diabetes in 1999

19. 19 Comparison to Previous Studies n Our forecasts suggest that 35.5 million people will have diagnosed diabetes in 2050, as compared to previous forecasts of l 12 million (Helms, 1992) l 29 million (Boyle et al., 2001) n Why are our forecasts higher than previous estimates? l Use 1999 prevalence and incidence data l Forecasts are by age (0–100 years and 101+), race/ethnicity (NHW, NHB, Hispanic, Other) l Diabetes prevalence is determined within a dynamic model — not assumed to remain constant or follow a linear trend

20. 20 Study Limitations n Relative risk of death from diabetes l Available only for adults l Not available by race/ethnicity n Uncertainty about the future l Population growth l Diabetes incidence (assumed to remain constant) l Relative risk of death for people with diabetes (assumed to remain constant)

21. 21 Summary and Conclusions n Forecasts suggest that the number of people with diabetes will more than triple between 1999 and 2050 l Rising from 10.9 million in 1999 to 35.5 million in 2050 n Diabetes prevalence is projected to grow from 4% to 9% from 1999 to 2050 l Race/ethnicity-specific: Highest projected prevalence among non-Hispanic blacks — increases from 5.6% in 1999 to 11.9% in 2050 l Age-specific — Largest increase for 75+ years — from 12.8% in 1999 to over 23% in 2050 n Findings suggest an increased demand for health care resources in the next 50 years to treat people with diabetes