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Diabetes --- United States, 2004 and 2008

Gloria L. Beckles, MD1

Julia Zhu, MS2

Ramal Moonesinghe, PhD3

1National Center for Chronic Disease Prevention and Health Promotion, CDC

2Epidemiology and Analysis Program Office, CDC

3Office of Minority Health and Health Disparities, CDC

Corresponding author: Gloria L. Beckles, MD, Division of Diabetes Translation, 1600 Clifton Road, NE, MS K-10, Atlanta, GA 30333. Telephone: 770-488-1272; Fax: 770-488-8364; E-mail: glb4@cdc.gov.

Diabetes is a serious, costly, and potentially preventable public health problem in the United States (1--3). Both the prevalence and incidence of diabetes have increased rapidly since the mid-1990s, with minority racial/ethnic groups and socioeconomically disadvantaged groups experiencing the steepest increases and most substantial effects from the disease (1,4--6).

To assess disparities in the prevalence and incidence of medically diagnosed diabetes, CDC used data from the 2004 and 2008 National Health Interview Survey (NHIS), an ongoing, cross-sectional, in-person household interview survey of the civilian, noninstitutionalized U.S. population. A randomly selected adult (aged ≥18 years) in each family was asked whether they had ever been told by a health-care professional that they had diabetes; those who reported having diagnosed diabetes were asked the age at which they received the diagnosis. Respondents who were the same age when interviewed as when they received a diabetes diagnosis were considered to have a case of incident diabetes (Age at interview -- Age at diagnosis = 0 years). In addition, half of the cases among respondents who were aged 1 year older when they were interviewed than when they received the diagnosis were counted as incident cases (Age at interview -- Age at diagnosis = 1 year). Both the values for age at interview and age at diagnosis were rounded to the nearest year; therefore, among respondents with a difference of 1 year (Age at interview -- Age at diagnosis = 1 year), the actual duration with diagnosed diabetes was in the interval (0, 2). Durations were assumed to be spread uniformly over the interval (0, 2), and half were assumed to be within 1 year of diagnosis. Prevalence (cases of diabetes of any duration per 100 population) was calculated for adults aged ≥18 years. Incidence (cases of diabetes ≤1 year's duration per 1,000 population) was calculated for adults aged 18--79 years.

Analyses were performed to assess disparities between groups, defined by age, sex, race/ethnicity, socioeconomic position (measured as educational attainment and poverty to income ratio [PIR]) (7), disability status, and U.S. Census region. Persons with a disability were adults with either a functional limitation from any condition or a health problem that required use of special equipment (8). In each disparity domain (i.e., classifying variable), the group with the lowest stable estimate (i.e., relative standard error <30%) of diabetes prevalence or incidence was chosen as the referent category; for racial/ethnic disparities, white men and white women, the largest groups, were selected as the referent category (9,10). Absolute difference was calculated by subtracting the value in the referent category from each category of the classifying variable. Relative difference (percentage difference) was calculated by dividing the absolute difference by the value in the referent category. For example, with women as the referent category, the relative difference in prevalence between men and women is the absolute difference divided by the value for women with the fraction expressed as a percentage. To assess whether disparities changed with time, the difference between group relative differences that were significant in the 2008 and 2004 data were calculated (9,10). Statistically significant increases and decreases in relative difference from 2004 to 2008 were interpreted as increases and decreases in disparity over time, respectively. In all analyses, data were weighted to provide estimates representative of the U.S. population. Estimates were age adjusted to the U.S. 2000 Census population (11). The z statistic and a two-tailed test with Bonferroni correction were used to test for statistical significance of absolute differences and the change in relative difference between 2004 and 2008. Differences were considered statistically significant at p<0.05.

Substantial racial/ethnic disparities were identified between the 2008 age-standardized prevalence of medically diagnosed diabetes for each nonwhite group and for whites (Table 1). Overall and for either sex, absolute differences were statistically significant (p<0.05) for blacks and Hispanics but not for Asians. Substantial socioeconomic disparities also were identified in the age-standardized prevalence of diagnosed diabetes. Statistically significant absolute differences increased with decreasing levels of education attained and levels of PIR; the greatest disparities were experienced by the groups who had the lowest level of education, were living below the federal poverty level, or both. Statistically significant differences in prevalence of diagnosed diabetes were also found, according to disability status, age, and U.S. Census region (i.e., the South in 2008). The absolute age-specific differences increased with age, reflecting the expected age-related increase in diabetes risk (1,12). The significant absolute difference in age-standardized prevalence of diagnosed diabetes between the groups with and without disability might reflect the association between diabetes and disability (13). The geographic disparity observed for the South is consistent with recent reports of geospatial variation in the prevalence of diagnosed diabetes (14). All relative disparities in prevalence demonstrated similar patterns.

Changes across time occurred in the racial/ethnic, age, and education disparities in the age-standardized prevalence of diagnosed diabetes observed for 2008 and 2004 (Table 1). Relative differences in the aged-standardized prevalence of diagnosed diabetes among Hispanic and black women were significantly lower during 2008 than 2004. No significant change occurred among men or among both sexes combined. The relative difference between the age-specific prevalence of diagnosed diabetes for the referent category (18--44 years) and each of the age groups (45--64, 65--74, and ≥75 years) was significantly lower during 2008 than 2004. However, the relative differences between the age-standardized prevalence of diagnosed diabetes among persons who had a high school education or less and the referent category (more than high school) were significantly higher during 2008 than 2004.

For 2008, statistically significant socioeconomic, age, and disability disparities were identified in the age-standardized incidence of diagnosed diabetes (Table 2). Absolute differences between the incidence rates of diagnosed diabetes in the groups with a high school education or less and the rate in the referent category (more than high school) were significant. Absolute differences between the incidence rates of diagnosed diabetes among the poor, near-poor, and middle income PIR categories and the incidence rate in the referent category (high income, PIR ≥4.0) were also significantly different. In addition, the absolute disparities in the age-standardized incidence rate of diagnosed diabetes increased progressively with decreasing levels of education and PIR; these disparities increased to >100% for the groups who did not complete high school or who lived below the federal poverty level (PIR < 1.0). The absolute disparities between the age-standardized incidence rates of diagnosed diabetes for adults aged 45--64 and 65--79 years and the rate among those aged 18--44 years were significant and increased with age, reflecting the age-related increased risk for diabetes (1,6). Finally, the incidence rate of diagnosed diabetes among the group with disabilities was significantly different from the rate in the group without disabilities. The relative disparities in incidence rates demonstrated similar patterning.

Socioeconomic, age, and disability disparities in the incidence rate of diagnosed diabetes increased from 2004 to 2008 (Table 2). The relative disparities in the age-standardized incidence rates of diagnosed diabetes among the groups who had a high school education or less increased more than twofold and threefold, respectively, from 2004 to 2008 (p<0.05 for both groups). The change was less consistent for the groups by income. The relative disparities for the lowest income group (PIR < 1.0) were not significantly different; however, relative disparities among the near-poor and middle income groups were more than threefold higher during 2008 than 2004 (p<0.05 for both groups). In 2008, the relative disparity for the group with disabilities was approximately twice the relative disparity during 2004 (p<0.05).

The findings in this report are subject to at least two limitations. First, all data are self-reported and therefore subject to recall and social desirability bias. However, self-reported diabetes data have been reported to have high reliability (15,16). Second, differences were not assessed for total prevalence of diabetes (i.e., diagnosed and undiagnosed); therefore, the findings might underestimate the extent of the disparities in prevalence and incidence among the U.S. population. The percentage of persons with undiagnosed diabetes is estimated to range from 24% to 40% of the total prevalence of diabetes (11,17). However, the racial/ethnic, socioeconomic, geographic, disability, and change over time of the disparities in prevalence and incidence of medically diagnosed diabetes are consistent with reports on diabetes risk among U.S. adults (1,4--6,12,13).

Marked sociodemographic disparities in prevalence and incidence of diagnosed diabetes exist among U.S. adults. Moreover, no evidence indicates that racial/ethnic disparities in prevalence and incidence of diagnosed diabetes decreased from 2004 to 2008, although socioeconomic disparities worsened during the same interval. Health promotion and risk-reduction efforts have been focused primarily on racial/ethnic minority groups identified as groups at high risk for diabetes. The findings in this report demonstrate that, despite these efforts, decreases in racial/ethnic disparities have been substantially limited. Increased awareness about the risk for diabetes among adults with low levels of income and educational attainment and those with disabilities might help decrease disparities. Interventions designed specifically for these groups might increase the effectiveness of efforts to reduce disparities in diabetes risk.

References

  1. CDC. National Diabetes Surveillance System. Atlanta, GA: US Department of Health and Human Services, CDC; 2010. Available at http://www.cdc.gov/diabetes/statistics/index.htm.
  2. Dall TM, Zhang Y, Chen YJ, Quick WW, Yang WG, Fogli J. The economic burden of diabetes. Health Aff 2010;29:297--303.
  3. Diabetes Prevention Program Research Group. Reduction in the incidence of type 2 diabetes with lifestyle intervention or metformin. N Engl J Med 2002;346:393--403.
  4. Kanjilal S, Gregg EW, Cheng YJ, et al. Socioeconomic status and trends in disparities in 4 major risk factors for cardiovascular disease among US adults, 1971--2002. Arch Intern Med 2006;166:2348--55.
  5. Narayan KM, Boyle JP, Geiss LS, Saaddine JB, Thompson TJ. Impact of recent increase in incidence on future diabetes burden: U.S., 2005--2050. Diabetes Care 2006;29:2114--6.
  6. Geiss LS, Pan L, Cadwell B, Gregg EW, Benjamin SM, Engelgau MM. Changes in incidence of diabetes in U.S. adults, 1997--2003. Am J Prev Med 2006;30:371--7.
  7. Dalaker J, Proctor BD. Poverty in the United States: 1999. Washington, DC: US Census Bureau; 2000. Current Population Reports P60, No. 210. Available at http://www.census.gov/hhes/www/poverty/publications/p60-210.pdf.
  8. CDC. Healthy people 2010. Operational definition. Available at http://ftp.cdc.gov/pub/health_statistics/nchs/datasets/data2010/focusarea06/O0601.pdf.
  9. Keppel K, Pamuk E, Lynch J, et al. Methodological issues in measuring health disparities. Vital Health Stat 2 2005;141:1--16.
  10. US Census Bureau. Current population survey: design and methodology. Washington, DC: US Census Bureau; 2006. Technical paper 66. Available at http://www.census.gov/prod/2006pubs/tp-66.pdf.
  11. Anderson RN, Rosenberg HM. Age standardization of death rates: implementation of the year 2000 standard. Natl Vital Stat Rep 1998;47:1--16, 20.
  12. Cowie CC, Rust KF, Ford ES, et al. Full accounting of diabetes and pre-diabetes in the U.S. population in 1988--1994 and 2005--2006. Diabetes Care 2009;32:287--94.
  13. Volpato S, Maraldi C, Fellin R. Type 2 diabetes and risk for functional decline and disability in older persons. Curr Diabetes Rev 2010;6:134--43.
  14. CDC. National Diabetes Surveillance System: county level estimates of diagnosed diabetes---U.S. maps. Atlanta, GA: US Department of Health and Human Services, CDC; 2010. Available at http://apps.nccd.cdc.gov/DDT_STRS2/NationalDiabetesPrevalenceEstimates.aspx?mode=DBT.
  15. Tisando DM, Adams JL, Liu H, et al. What is the concordance between the medical record and patient self-report as data sources for ambulatory care? Med Care 2006;44:132--40.
  16. Newell SA, Girgis A, Sanson-Fisher RW, Savolainen NJ. The accuracy of self-reported health behaviors and risk factors relating to cancer and cardiovascular disease in the general population. A critical review. Am J Prev Med 1999;17:211--29.
  17. CDC. National Diabetes Surveillance System: national diabetes fact sheet, 2007. Atlanta, GA: US Department of Health and Human Services, CDC; 2008. Available at http://www.cdc.gov/diabetes/pubs/pdf/ndfs_2007.pdf.

* Preliminary data for 2008 indicate that stroke might now be the fourth leading cause of death in the United States. However, these data should be interpreted with caution. (Data available at http://www.cdc.gov/nchs/data/nvsr/nvsr59/nvsr59_02.pdf.)

Additional information is available at http://www.cdc.gov/nchs/nhanes.htm.

§ The response rate is the percentage of persons who were examined among all sampled persons.

Family income: the combined income of all persons within a household who are related to each other by blood, marriage, or adoption. Poverty level: family income relative to family size and age of the members adjusted for inflation using the poverty thresholds developed by the U.S. Bureau of the Census.

** Private health insurance: private health insurance or Medigap insurance. Public health insurance: Medicare, Medicaid, State Children's Health Insurance Program, military health care, state-sponsored health plan, or other government insurance.

†† Disability: the inability to work at a job or business because of a physical, mental, or emotional problem; limitation caused by difficulty remembering or periods of confusion; limitation in any activity because of a physical, mental, or emotional problem; or use of special equipment (e.g., cane, wheelchair, special bed, or special telephone).

§§ Persons with diabetes: those who have ever been told by a health-care professional that they have diabetes. Persons without diabetes: those who have never been told by a health-care professional that they have diabetes or have never been told that they have borderline diabetes.

¶¶ Obesity: body mass index ≥30 kg/m2 based on measured weight and height.

*** Additional information is available at http://www.nyc.gov/html/doh/html/cardio/cardio-salt-initiative-comp-commitments.shtml.


TABLE 1. Age-adjusted prevalence* of medically diagnosed diabetes among adults aged ≥18 years, by selected characteristics --- National Health Interview Survey, United States, 2004 and 2008

Characteristic

2004

2008

Change in relative difference from 2004 to 2008

Age-adjusted %

(95% CI)

Absolute difference

Relative difference %

Age-adjusted %

(95% CI)

Absolute difference

Relative difference %

Sex

Male

7.5

(6.9--8.1)

1.1

17.2

8.1

(7.5--8.7)

0.4

5.2

--12.0

Female

6.4

(6.0--6.8)

Ref.

Ref.

7.7

(7.1--8.3)

Ref.

Ref.

Ref.

Race/Ethnicity

Both sexes

White

6.0

(5.6--6.4)

Ref.

Ref.

7.0

(6.6--7.4)

Ref.

Ref.

Ref.

Black

10.6

(8.8--12.4)

4.6

76.7

11.0

(9.6--12.4)

4.0

57.1

--19.6

Asian

8.9

(4.2--13.6)

2.9

48.3

8.2

(6.0--10.2)

1.2

17.1

--31.2

Hispanic§

10.3

(8.5--12.1)

4.3

71.7

10.7

(9.3--12.1)

3.7

52.9

--18.6

Male

White

6.7

(6.1--7.3)

Ref.

Ref.

7.3

(6.5--8.0)

Ref.

Ref.

Ref.

Black

10.3

(8.3--12.3)

3.6

53.7

10.4

(8.4--12.4)

3.2

43.8

--9.8

Asian

8.8

(6.8 --10.8 )

2.1

31.3

9.4

(6.5--12.3)

2.1

28.8

--2.5

Hispanic

10.0

(8.0--12.0)

3.3

49.3

11.1

(8.9--13.3)

3.8

52.1

2.8

Female

White

5.4

(4.8--6.0)

Ref.

Ref.

6.7

(6.1--7.3)

Ref.

Ref.

Ref.

Black

10.7

(9.1--12.3)

5.3

98.1

11.4

(9.8--13.0)

4.7

70.1

--28.0

Asian

8.6

(2.1--15.1)

3.2

59.3

7.2

(4.9--9.6)

0.5

7.5

--51.8

Hispanic

10.5

(8.9--12.1)

5.1

96.4

10.5

(9.9--11.1)

3.8

56.7

--39.7

Education level

<High school

9.7

(8.7--10.7)

3.7

61.7

11.8

(11.4--12.2)

5.6

90.3

28.6

High school

7.0

(6.4--7.6)

1.0

16.7

9.0

(8.8--9.2)

2.8

45.2

28.5

>High school

6.0

(5.6--6.4)

Ref.

Ref.

6.2

(6.1--6.3)

Ref.

Ref.

Ref.

Poverty to income ratio**

Poor, <1

11.4

(9.8--13.0)

5.9

107.3

11.7

(10.3--13.1)

6.2

112.7

5.4

Near-poor, 1.0--1.9

9.0

(7.2--10.8)

3.5

63.6

10.4

(8.6--12.2)

4.9

89.1

25.5

Middle income, 2.0--3.9

6.5

(5.7--7.3 )

1.0

18.2

8.3

(7.5--9.1)

2.8

50.9

32.7

High income, ≥4.0

5.5

(4.7--6.3)

Ref.

Ref.

5.5

(4.9--6.1)

Ref.

Ref.

Ref.

Disability status

Disability

10.5

(9.1--11.9)

6.1

138.6

12.5

(10.7--14.3)

7.8

166.0

27.4

No disability

4.4

(3.6--5.2)

Ref.

Ref.

4.7

(3.9--5.5)

Ref.

Ref.

Ref.

Age group (yrs)††

18--44

1.9

(1.3--2.5)

Ref.

Ref.

2.3

(1.5--3.1)

Ref.

Ref.

Ref.

45--64

10.1

(8.5--11.7)

8.2

431.6

12.0

(10.2--13.8)

9.7

421.7

--9.9

65--74

18.2

(14.5--21.9)

16.3

857.9

19.8

(16.3--23.3)

17.5

760.9

--97.0

≥75

16.0

(12.5--19.5)

14.1

742.1

16.9

(13.4--20.4)

14.6

634.8

--107.3

U.S. Census region

Northeast

6.1

(5.3--6.9)

Ref.

Ref.

7.2

(6.2--8.2)

Ref.

Ref.

Ref.

Midwest

6.9

(6.1--7.7)

0.8

13.1

7.4

(6.6--8.2)

0.2

2.8

--10.3

South

7.8

(7.2--8.4)

1.7

27.9

8.7

(7.9--9.5)

1.5

20.8

--7.1

West

6.1

(5.9--6.3)

0

0

7.5

(6.7--8.3)

0.3

0

0

Abbreviation: CI = confidence interval.

* Cases of diabetes of any duration per 100 population.

Difference between group estimate and referent category significant at p<0.05 by z statistic and a two-tailed test with Bonferroni correction.

§ Persons of Hispanic ethnicity might be of any race.

Difference between the relative differences in 2008 and 2004 significant at p<0.05 by z statistic and a two-tailed test with Bonferroni correction.

** On the basis of the U.S. poverty level.

†† Age-specific estimates are not age adjusted.


TABLE 2. Age-standardized incidence rate* of medically diagnosed diabetes among adults aged 18--79 years, by selected characteristics --- National Health Interview Survey, United States, 2004 and 2008

Characteristic

2004

2008

Change in relative difference from 2004 to 2008

Age-adjusted incidence rate

(95% CI)

Absolute difference

Relative difference (%)

Age-adjusted incidence rate

(95% CI)

Absolute difference

Relative difference (%)

Sex

Male

8.3

(8.1--8.5)

1.5

22.1

8.4

(8.2--8.6)

0.3

3.7

--18.4

Female

6.8

(6.6--7.0)

Ref.

Ref.

8.1

(7.9--8.3)

Ref.

Ref.

Ref.

Race/Ethnicity

Both sexes

White

6.5

(6.3--6.7)

Ref.

Ref.

8.0

(7.8--8.2)

Ref.

Ref.

Ref.

Black

8.2

(7.8--8.6)

1.7

26.2

8.0

(7.6--8.4)

0

0

--26.2

Hispanic

11.1

(10.5--1.7)

4.6

70.8

11.5

(11.1-- 11.9)

3.5

43.8

--27.0

Male

White

7.7

(7.5--7.9)

Ref.

Ref.

8.0

(7.8--8.2)

Ref.

Ref.

Ref.

Black

9.6

(8.8--10.4)

1.9

24.7

7.0

(6.6--7.4)

--1.0

12.5

--12.2

Hispanic

7.3

(6.9--7.7)

--0.4

5.2

13.2)

(12.6--13.8)

6.2

77.5

72.3

Female

White

5.4

(5.2--5.6)

Ref.

Ref.

8.2

(8.0--8.4)

Ref.

Ref.

Ref.

Black

7.0

(6.6--7.4)

1.6

29.6

8.9

(8.5--9.3)

0.7

8.5

--21.1

Hispanic

14.6

(13.8--15.4)

9.2

170.4

13.1

(12.5--13.7)

4.9

59.8

110.6

Education level

<High school

10.7

(10.3--11.1)

4.0§

59.7

15.1

(14.5--15.7)

8.9§

143.5

83.8

High school

7.9

(7.7--8.1)

1.2

17.9

10.2

(9.8--10.6)

4.0§

64.5

46.6

>High school

6.7

(6.5--6.9)

Ref.

Ref.

6.2

(6.0--6.4)

Ref.

Ref.

Ref.

Poverty to income ratio**

Poor, <1.0

10.7

(9.9 --11.5)

5.1§

91.1

11.2

(10.6--11.8)

5.8§

107.4

16.3

Near poor, 1.0--1.9

12.1

(11.3--12.9)

6.5§

116.1

9.3

(9.1--9.7)

3.9§

72.2

--43.9

Middle income, 2.0--3.9

6.9

(6.3--7.5)

1.3§

23.2

9.9

(9.5 --10.3)

4.5§

83.3§

60.1

High income, ≥4.0

5.6

(5.2--6.0)

Ref.

Ref.

5.4

(5.2--5.6)

Ref.

Ref.

Ref.

Disability status

Disability

12.4

(11.8--13.0)

7.0§

129.6

14.9

(14.3--15.5)

10.4§

233.3

103.7

No disability

5.4

(5.2--5.6)

Ref.

Ref.

4.5

(4.3--4.7)

Ref.

Ref.

Ref.

Age group (yrs)††

18--44

3.7

(3.5--3.9)

Ref.

Ref.

3.7

(3.5 --3.9)

Ref.

Ref.

Ref.

45--64

12.2

(11.6--12.8)

8.5§

229.7

14.7

(14.1--15.3)

11.0§

297.3

67.6

65--79

13.4

(12.8--14.0)

9.7§

262.2

13.5

(12.7--14.3)

9.8§

264.9

2.7

U.S. Census region

Northeast

6.0

(5.8--6.2)

--0.4

6.3

9.5

(9.1--9.9)

2.3

31.9

25.6

Midwest

7.1

(6.9--7.3)

0.7

10.9

8.2

(8.0--8.4)

1.0

13.9

3.0

South

9.4

(9.2--9.6)

3.0

46.9

8.7

(8.5--8.9)

1.5

20.8

--26.1

West

6.4

(6.2--6.6)

Ref.

Ref.

7.2

(7.0--7.4)

Ref.

Ref.

Ref.

Abbreviation: CI = confidence interval.

* Per 1,000 population.

Persons of Hispanic ethnicity might be of any race.

§ Difference between group estimate and reference group estimate significant at p<0.05 by z statistic and a two-tailed test with Bonferroni correction.

Difference between the group relative differences in 2008 and 2004 significant at p<0.05 by z statistic and a two-tailed test with Bonferroni correction.

** On the basis of the U.S. poverty level.

†† Age-specific estimates are not age adjusted.



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