Physical activity, body mass index and waist circumference change, and normal-range glycated hemoglobin on incident diabetes: Jackson Heart Study

ABSTRACT

Objectives: The purpose of this study was to 1) evaluate whether physical activity has a protective effect on incident diabetes among African Americans across combinations of body mass index (BMI) and waist circumference (WC), 2) evaluate the effect of changes on BMI and WC on incident diabetes, and 3) evaluate the effect of ‘normal range’ glycated hemoglobin (A1C) on incident diabetes.

Methods: Data from the prospective Jackson Heart Study were evaluated, with baseline data assessed between 2001 and 2004 and follow-up data occurring between 2009 and 2013. Physical activity was assessed via a validated questionnaire, with measured BMI, WC and A1C assessed via standard procedures.

Results: The sample included 2,450 adults who did not have evidence of diabetes at the baseline assessment, with 286 incident diabetes cases occurring at the follow-up assessment. Physical activity did not have a protective effect against incident diabetes across different BMI and WC combinations. Notably, BMI change from baseline to follow-up was associated with incident diabetes (HR = 1.08; 95% CI: 1.03–1.13). Further, higher levels of A1C within the ‘normal-range’ was associated with incident diabetes (HR = 7.51, 95% CI = 2.66–21.25).

Conclusion: Increases in BMI over time and higher A1C within the normal range were associated with incident diabetes. Serial monitoring of BMI, as well as A1C, even among those with a ‘normal’ A1C, may be warranted by clinicians. Future work evaluating this novel three-way model (physical activity, BMI and WC) should consider utilizing an objective measure of physical activity.

KEYWORDS:

• African Americans
• glycemic control
• epidemiology
• exercise

Acknowledgments

The Jackson Heart Study (JHS) is supported and conducted in collaboration with Jackson State University (HHSN268201300049C and HHSN268201300050C), Tougaloo College (HHSN268201300048C), and The University of Mississippi Medical Center (HHSN268201300046C and HHSN268201300047C) contracts from the National Heart, Lung, and Blood Institute (NHLBI) and the National Institute for Minority Health and Health Disparities (NIMHD). The authors also wish to thank the staffs and participants of the JHS.

The views expressed in this manuscript are those of the authors and do not necessarily represent the views of the National Heart, Lung, and Blood Institute; the National Institutes of Health; or the U.S. Department of Health and Human Service.

Declaration of interest

The authors have no other relevant affiliations or financial involvement with any organization or entity with a financial interest in or financial conflict with the subject matter or materials discussed in the manuscript apart from those disclosed.

Additional information

Funding

AG Bertoni reports grants from National Institutes of Health (R01 HL117285-01) during the conduct of this study.