Danish Medical Bulletin - No. 2. June 2004. Vol. 51 Page 211.

ABSTRACT OF PhD DISSERTATION

Fat distribution
and all-cause mortality

Janne Bigaard

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This PhD dissertation was accepted by the Faculty of Health Sciences of the University of Copenhagen, and defended on January 23, 2004.

Official opponents: Jaap Seidell, the Netherlands, Finn Rasmussen, Stockholm, and Finn Gyntelberg.

Tutors: Anne Tjønneland, Berit Heitmann and Thorkild I.A. Sørensen.

Correspondence: Janne Bigaard, Institute of Cancer Epidemiology, Danish Cancer Society, Strandboulevarden 49, DK-2100 Copenhagen Ø.
E-mail: janne@cancer.dk

Dan Med Bull 2004;51:211.

ABSTRACT

This PhD dissertation summarises the results of four papers investigating associations between fat distribution and all-cause mortality. Waist circumference was introduced as an alternative risk indicator to replace body mass index (BMI) but adequate evidence for its utility, as a risk indicator for obesity, has not been provided. The main aim of this dissertation was to investigate the association between waist circumference and all-cause mortality.

We used data from the Danish prospective study "Diet, Cancer and Health" 1993-1997 with 57,053 participants aged 50 to 64 years, and without a previous cancer registered in the Danish Cancer Registry. The cohort represents 7% of the entire Danish population in this age group.

Waist circumference was strongly associated with all-cause mortality; increasing mortality risk was found with increasing values of waist circumference after adjustment for BMI. A U-shaped association was found between BMI and all-cause mortality. This could be disentangled into two joints, but separate associations of body composition. All-cause mortality increased with increasing values of body fat mass adjusted for fat-free mass, whereas the mortality decreased with increasing values of fat-free mass adjusted for body fat. When the associations between body composition and mortality were further adjusted for waist circumference, waist circumference eliminated the association between high values of body fat mass and mortality, but did not influence the association between fat-free mass and mortality, and a strong association remained between waist circumference and mortality. An inverse association was found between hip circumference and mortality after adjustment for waist circumference, BMI, or both. Hip and waist circumference had opposite associations with mortality, not always captured adequately by the WHR.

In conclusion, these studies provided a better understanding of the associations between fat distribution and all-cause mortality in middle-aged men and women. The combination of waist circumference and BMI predicts the health risk associated with obesity in middle-aged men and women in the total range of waist circumference. Waist circumference eliminated the association between high values of body fat mass index and mortality, indicating that waist circumference reflects total body fat. However, a strong association remained between waist circumference and all-cause mortality after adjustment for body composition suggesting that waist circumference reflects fat deposits elsewhere in addition to total body fat, for example visceral fat. Health risk associated with fat distribution is important to consider besides risk associated with BMI.
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