Since 1988, two studies have assessed trends in age at diagnosis in the U.S. among adults with probable type 2 diabetes (T2D) (1,2). From 1988 to 2000, the mean age of adults who received a T2D diagnosis was reported to decrease from 52 to 46 years (1). From 2001 to 2016, overall mean age at T2D diagnosis was stable, roughly 50.5 years (2). There are gender differences in T2D; T2D is more prevalent in men, but women have a younger age at diagnosis. Assessing whether trends in age at T2D diagnosis differ by gender can identify shifts in age-related disease burden and help inform clinical and public health preventive strategies. Our objective was to assess for gender differences in the trend in age at T2D diagnosis among individuals 18 years of age and older.
We included 11 cycles of data from the repeated cross-sectional population-based National Health and Nutrition Examination Survey (NHANES) from 1999 to 2000 through 2017 to March 2020. Of the 7,359 NHANES participants with a self-reported diagnosis of diabetes during this period, we excluded 124 individuals for missing data on age at diagnosis, 4 of whom had data on insulin medication use missing, 3 who were pregnant within 1 year of their examination, 233 with possible type 1 diabetes (>30 years of age at diagnosis with insulin use within 1 year of diagnosis), and 38 who were younger than 18 years of age at the time of exam. We used linear regression to estimate age at diabetes diagnosis for each NHANES cycle and assessed trends in age at diagnosis between 1999 and March 2020. Analyses were adjusted for race and gender and included an interaction term between gender and NHANES cycle. Gender-specific analyses were adjusted for race. We assessed whether differences in diabetes duration over time can explain any observed association.
The analytic sample included 6,957 NHANES participants (mean age 62.8 years; 51% male). In 1999–2000, the adjusted mean age at diabetes diagnosis was 47.6 years (95% CI 45.8, 49.5), and these estimates remained steady through March 2020 (per annum 0.07; 95% CI –0.02, 0.17). The assessment of the trend in age at diabetes diagnosis for effect modification by gender yielded P = 0.09. Age at diabetes diagnosis remained steady for women (per annum 0.00; 95% CI –0.12, 0.12) and increased for men by 0.14 years (95% CI 0.01, 0.27) per annum between 1999 and March 2020 (Fig. 1). Mean diabetes duration was 12.2 years (SE 0.9) in 1999–2000, remained steady (per annum 0.04; 95% CI –0.03, 0.11), and did not differ by gender (interaction P = 0.26) over time.
Self-reported age at diagnosis of diabetes by gender and duration of diabetes among NHANES adult participants from 1999 to 2020.
Self-reported age at diagnosis of diabetes by gender and duration of diabetes among NHANES adult participants from 1999 to 2020.
In this representative sample of U.S. adults with a self-reported diagnosis of diabetes, the mean self-reported age at diagnosis remained steady from 1999 to 2020. However, there is evidence of gender differences in trends of self-reported age at diabetes diagnosis; the self-reported age at diabetes diagnosis remained steady among women and increased among men. Gender differences in diabetes duration do not appear to explain this association. Women are diagnosed with diabetes at a younger age than men (3). Whether our findings support a shift in the epidemiology of T2D pathology, such as better prevention of diabetes for men than women or changes in T2D screening, is not readily apparent. Reports are mixed on gender differences in screening, but since 1999 there has been a greater increase in the prevalence of diagnosed diabetes among men than women and a concurrent decrease in the prevalence of undiagnosed diabetes for men but not for women (4). Our findings may also be the result of an aging U.S. population and gender differences for better survival for other chronic conditions, leading to men receiving a diabetes diagnosis that previously would not have occurred before early death.
Study limitations include self-reported information for age at diabetes diagnosis, although self-report of diabetes has been shown to have high validity compared with laboratory measurements, medication inventory, and medical records (5). NHANES does not differentiate between diabetes type, and we excluded individuals with possible gestational diabetes mellitus and type 1 diabetes based on pregnancy status, age at diagnosis, and insulin use, similar to prior studies on this topic (1,2). Lastly, analyses are limited to adults with diagnosed diabetes.
Article Information
Acknowledgments. The authors thank the other investigators, the staff, and the participants of the NHANES study for their valuable contributions.
Funding. The Short-Term Research Experience Program to Unlock Potential (STEP-UP high school) program is supported by the National Institute of Diabetes and Digestive and Kidney Diseases of the National Institutes of Health, grant number R25DK113659.
The views expressed in this article are those of the authors and do not necessarily represent the views of the Centers for Disease Control and Prevention, the National Heart, Lung, and Blood Institute, the National Institutes of Health, or the U.S. Department of Health and Human Services.
Duality of Interest. No potential conflicts of interest relevant to this article were reported.
Author Contributions. Authors made the following contributions: concept and design, A.R.M. and M.P.B.; acquisition, analysis, or interpretation of data, A.R.M. and M.P.B.; drafting of the manuscript, A.R.M.; critical revision of the manuscript for important intellectual content, A.R.M. and M.P.B.; statistical analysis, M.P.B.; and supervision, M.P.B. Both authors made substantial intellectual contributions, participated in creating and designing the study, analyzed and interpreted the data, and reviewed the manuscript. M.P.B. is the guarantor of this work and, as such, had full access to all the data in the study and takes responsibility for the integrity of the data and the accuracy of the data analysis.
Prior Presentation. Preliminary findings of this project were presented as a virtual oral presentation for the National Institute of Diabetes and Digestive and Kidney Diseases Short-Term Research Experience Program to Unlock Potential research program.
