Secular changes in the age-specific prevalence of diabetes among U.S. adults: 1988-2010

Abstract

Objective: To examine the age-specific changes of prevalence of diabetes among U.S. adults during the past 2 decades.

Research design and methods: This study included 22,586 adults sampled in three periods of the National Health and Nutrition Examination Survey (1988-1994, 1999-2004, and 2005-2010). Diabetes was defined as having self-reported diagnosed diabetes or having a fasting plasma glucose level ≥ 126 mg/dL or HbA1c ≥ 6.5% (48 mmol/mol).

Results: The number of adults with diabetes increased by 75% from 1988-1994 to 2005-2010. After adjusting for sex, race/ethnicity, and education level, the prevalence of diabetes increased over the two decades across all age-groups. Younger adults (20-34 years of age) had the lowest absolute increase in diabetes prevalence of 1.0%, followed by middle-aged adults (35-64) at 2.7% and older adults (≥ 65) at 10.0% (all P < 0.001). Comparing 2005-2010 with 1988-1994, the adjusted prevalence ratios (PRs) by age-group were 2.3, 1.3, and 1.5 for younger, middle-aged, and older adults, respectively (all P < 0.05). After additional adjustment for body mass index (BMI), waist-to-height ratio (WHtR), or waist circumference (WC), the adjusted PR remained statistically significant only for adults ≥ 65 years of age.

Conclusions: During the past two decades, the prevalence of diabetes increased across all age-groups, but adults ≥ 65 years of age experienced the largest increase in absolute change. Obesity, as measured by BMI, WHtR, or WC, was strongly associated with the increase in diabetes prevalence, especially in adults <65.

Figure 1

Total number of adults ≥20 years of age with diabetes by survey year: U.S. NHANES, 1988–2010. Each dot of 1988–1994 (△), 1999–2004 (◇), and 2005–2010 (○) represents the total number of adults with diabetes within a 5-year age-group. Each line for 1988–1994 (dotted), 1999–2004 (dashed), and 2005–2010 (solid) represents the smoothed trend line of the total number of adults with diabetes derived from a cubic polynomial regression by age-group (AgeGrp) from 1 (20–24 years) to 13 (≥80 years) for each time period. For 1988–1994, −3,893.6*AgeGrp3 + 52,915*AgeGrp2 + 53,590*AgeGrp – 85,885; for 1999–2004, −3,254.7*AgeGrp3 + 30,451*AgeGrp2 + 274,991*AgeGrp – 263,749; and for 2005–2010, −5,520.1*AgeGrp3 + 68,979*AgeGrp2 + 204,097*AgeGrp – 253,127.

Figure 2

Age-specific unadjusted and sex-, race/ethnicity-, and education-adjusted prevalence of diabetes in adults ≥20 years of age by survey year: U.S. NHANES, 1988–2010. Each dot of 1988–1994 (△), 1999–2004 (◇), and 2005–2010 (○) represents the unadjusted prevalence within a 5-year age-group. Each line for 1988–1994 (dotted), 1999–2004 (dashed), and 2005–2010 (solid) represents the sex-, race/ethnicity-, and education-adjusted predicted prevalence of the midpoint of the 5-year age-group from piecewise regression, with age as a continuous variable.