Objectively Measured Sedentary Time May Predict Insulin Resistance Independent of Moderate- and Vigorous-Intensity Physical Activity

  1. Hendrik J.F. Helmerhorst1,2,
  2. Katrien Wijndaele1,
  3. Søren Brage1,
  4. Nicholas J. Wareham1 and
  5. Ulf Ekelund1
  1. 1Medical Research Council Epidemiology Unit, Cambridge, U.K.;
  2. 2Department of Endocrinology and Metabolism, Faculty of Medicine, Academic Medical Center, University of Amsterdam, the Netherlands.
  1. Corresponding author: Ulf Ekelund, ulf.ekelund{at}mrc-epid.cam.ac.uk.

Abstract

OBJECTIVE To examine the prospective association between objectively measured time spent sedentary and insulin resistance and whether this association is independent of moderate- and vigorous-intensity physical activity (MVPA) and other relevant confounders.

RESEARCH DESIGN AND METHODS This was a population-based study (Medical Research Council Ely study) in 376 middle-aged adults (166 men; 210 women) over 5.6 years of follow-up. Physical activity and sedentary time were measured objectively by individually calibrated minute-by-minute heart rate monitoring at both baseline and follow-up. Sedentary time was calculated as the heart rate observations (in minutes) below an individually predetermined threshold (flex heart rate) and expressed as a percentage of total monitored time during waking hours over 4 days. The percentage of time spent above 1.75 × resting heart rate represented MVPA. Fasting plasma insulin was used as a surrogate measure of insulin resistance.

RESULTS Time spent sedentary at baseline was significantly and positively associated with log fasting insulin at follow-up (β = 0.003, 95% CI 0.0006–0.006, P = 0.015) independent of baseline age, sex, fat mass, fasting insulin, smoking status, and follow-up time. After further adjustment for MVPA, this association was somewhat strengthened (β = 0.004, 95% CI 0.0009–0.006, P = 0.009).

CONCLUSIONS Time spent sedentary predicts higher levels of fasting insulin independent of the amount of time spent at moderate- and vigorous-intensity activity levels. This highlights the importance of reducing sedentary time in order to improve metabolic health, possibly in addition to the benefits associated with a physically active lifestyle.

Footnotes

  • The costs of publication of this article were defrayed in part by the payment of page charges. This article must therefore be hereby marked “advertisement” in accordance with 18 U.S.C. Section 1734 solely to indicate this fact.

    • Received December 22, 2008.
    • Accepted April 26, 2009.
  • Readers may use this article as long as the work is properly cited, the use is educational and not for profit, and the work is not altered. See http://creativecommons.org/licenses/by-nc-nd/3.0/ for details.

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  1. Diabetes vol. 58 no. 8 1776-1779
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