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Body Mass Index Is Inversely Related to Mortality in Older People After Adjustment for Waist Circumference

Authors

  • Ian Janssen PhD,

    1. From the *School of Physical and Health Education, Department of Community Health and Epidemiology, and Department of Medicine, Division of Endocrinology and Metabolism, Queen's University, Kingston, Ontario, Canada.
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  • Peter T. Katzmarzyk PhD,

    1. From the *School of Physical and Health Education, Department of Community Health and Epidemiology, and Department of Medicine, Division of Endocrinology and Metabolism, Queen's University, Kingston, Ontario, Canada.
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  • Robert Ross PhD

    1. From the *School of Physical and Health Education, Department of Community Health and Epidemiology, and Department of Medicine, Division of Endocrinology and Metabolism, Queen's University, Kingston, Ontario, Canada.
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  • Funded by the Canadian Institutes of Health Research.

Address correspondence to Ian Janssen, PhD, School of Physical and Health Education, Queen's University, Kingston, Ontario, Canada, K7L 3N6. E-mail: janssen@post.queensu.ca

Abstract

Objectives: To examine the individual and combined influence of body mass index (BMI) and waist circumference (WC) on mortality risk in older people.

Design: Longitudinal cohort study.

Setting: Cardiovascular Health Study, a longitudinal study of cardiovascular disease and its risk factors in older people.

Participants: Five thousand two hundred men and women aged 65 and older.

Measurements: BMI and WC were measured at baseline. The risks of all-cause mortality associated with BMI and WC were examined using Cox proportional hazards models over 9 years of follow-up.

Results: When examined individually, BMI and WC were both negative predictors of mortality, but when BMI and WC were examined simultaneously, BMI was a negative predictor of mortality, whereas WC was a positive predictor of mortality. After controlling for WC, mortality risk decreased 21% for every standard deviation increase in BMI. After controlling for BMI, mortality risk increased 13% for every standard deviation increase in WC. The patterns of associations were consistent by sex, age, and disease status.

Conclusion: Higher BMI values indicated a lower mortality risk once the risk attributable to WC was accounted for, whereas higher WC values indicate a higher mortality risk once the risk attributable to BMI was accounted for. Both BMI and WC should be measured in the clinical setting, but in older adults higher BMI is associated with lower mortality rates.

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