Background/objectives: This cohort study was conducted to evaluate the effect of waist change on metabolic syndrome (MetS) status and its parameters in 5720 participants, aged >or=20 years, of the Tehran Lipid and Glucose Study who were followed up for a mean of 6.6 years.
Subjects/methods: We measured waist circumference (WC) and MetS parameters at baseline (phase I: 1999) and at follow-up (phase III: 2008), and assessed this relationship across five groups: waist loss (<-2.0 cm); waist stable (-2.0 to 2.9 cm); mild (3.0-5.9 cm); moderate (6.0-8.9 cm) and large (>or=9.0 cm) waist gain. MetS was defined according to the International Diabetes Federation criteria.
Results: In phase I, the mean (s.d.) waist gain was 88.8 cm (11.7). Between phases I and III, the mean (s.d.) waist gain was 5 cm (7.9). There was 16% (95% confidence interval (95% CI): 13.6-18.4) age-adjusted incident MetS and for every centimeter of WC gained over 6.6 years, the risk of MetS increased by 10% (odds ratio (OR) 1.10; 95% CI: 1.09-1.12). Compared with a stable WC in both genders, ORs for MetS for different waist gain groups were as follows: mild (OR 2.3, 95% CI: 1.7-3.2); moderate (OR 3.5, 95% CI: 2.6-4.7) and large (OR 5.8, 95% CI: 4.5-7.6). Waist loss had a protective effect on MetS (OR 0.6, 95% CI: 0.4-0.9). Waist gain showed a detrimental effect on all parameters of MetS in both genders, except for high-density lipoprotein cholesterol and fasting blood sugar in women.
Conclusions: Waist gain, even mild, was a risk factor of the development of MetS and its parameters. Intervention for reducing WC could be an effective strategy to decrease incident MetS.