The dynamics of diabetes among birth cohorts in the U.S

Abstract

OBJECTIVE Using a nationally representative sample of the civilian noninstitutionalized U.S. population, we estimated trends in diabetes prevalence across cohorts born 1910-1989 and provide the first estimates of age-specific diabetes incidence using nationally representative, measured data. RESEARCH DESIGN AND METHODS Data were from 40,130 nonpregnant individuals aged 20-79 years who participated in the third National Health and Nutrition Examination Survey (NHANES III), 1988-1994, and the continuous 1999-2010 NHANES. We defined diabetes as HbA1c ≥6.5% (48 mmol/mol) or taking diabetes medication. We estimated age-specific diabetes prevalence for the 5-year age-groups 20-24 through 75-79 for cohorts born 1910-1919 through 1980-1989 and calendar periods 1988-1994, 1999-2002, 2003-2006, and 2007-2010. We modeled diabetes prevalence as a function of age, calendar year, and birth cohort, and used our cohort model to estimate age-specific diabetes incidence. RESULTS Age-adjusted diabetes prevalence rose by a factor of 4.9 between the birth cohorts of 1910-1919 and 1980-1989. Diabetes prevalence rose with age within each birth cohort. Models based on birth cohorts show a steeper age pattern of diabetes prevalence than those based on calendar years. Diabetes incidence peaks at 55-64 years of age. CONCLUSIONS Diabetes prevalence has risen across cohorts born through the 20th century. Changes across birth cohorts explain the majority of observed increases in prevalence over time. Incidence peaks between 55 and 64 years of age and then declines at older ages.

Figure 1

Trends in age-specific diabetes prevalence in successive observation periods of NHANES (A) and successive 10-year birth cohorts (B). Estimates were weighted to the U.S. population. Diabetes status determined by HbA_1c ≥6.5% (48 mmol/mol) or taking diabetes medication.

Figure 2

Age-adjusted diabetes prevalence in birth cohorts relative to those born 1910–1919. The graph shows the age-adjusted prevalence of diabetes in each birth cohort as a multiple of the age-adjusted prevalence for the 1910–1919 birth cohort.

Figure 3

Age-adjusted diabetes prevalence in periods relative to 1988–1994 (A); age-specific diabetes prevalence relative to age 20–24 years (B). A: Age-adjusted prevalence as a multiple of age-adjusted prevalence in the reference 1988–1994 period for the age/period model (diamonds) and age/period/cohort model (squares). B: Age-specific prevalence as a multiple of the prevalence at age 20–24 years in the age/cohort model (triangles), age/period model (diamonds), and age/period/cohort model (squares).

Figure 4

Smoothed age pattern of diabetes incidence using prevalence values from age/cohort model. Incidence estimated from age/cohort model of diabetes prevalence and differential mortality estimates, detailed in Research Design and Methods. Three-term moving average of incidence is plotted. For graphical purposes, incidence values are plotted for the cohort born in 1950–1959, but the shape of the curve is nearly identical for all birth cohorts.