Adiposity and carotid atherosclerosis in two populations at very different risk of cardiovascular mortality: Norway and Russia

• Main Author: Imahori, Y
• Format: Thesis
• Language: English
• Published: 2019
• Subjects: Norway; Tromsø
• Online Access: https://researchonline.lshtm.ac.uk/id/eprint/4654524/; https://researchonline.lshtm.ac.uk/id/eprint/4654524/1/2019_EPH_PhD_Imahori_Y.pdf

Obesity is a key risk factor for cardiovascular disease (CVD). The aim of this PhD study was to investigate the associations of obesity and adiposity with carotid atherosclerosis, and, in particular, to examine the effect of general vs abdominal adiposity on the burden of carotid plaque. These associations were investigated in the Tromsø study in Norway and in the Know Your Heart study in Russia. These populations have very different cardiovascular mortality rates, with Russia having one of the highest rates in the world. In this context, the thesis looked at whether differences in carotid plaque burden between these populations can be explained by adiposity. Four anthropometric measures of adiposity were included, which involved body mass index, waist circumference, waist-to-hip ratio, and waist-to-height ratio. Carotid plaque burden, i.e. the presence of plaques, number of plaques, and total plaque area (TPA), was assessed using carotid ultrasound. In the Tromsø Study 5th survey (2001), there was strong evidence of an association between TPA and adiposity, especially abdominal adiposity, after adjustment for potential confounders (sex, smoking status, education). This association was largely mediated by cardio-metabolic CVD risk factors (blood pressure, cholesterol, glycosylated haemoglobin). These findings were confirmed in a prospective analysis assessing changes in plaque burden between the Tromsø Study 4th (1994-95) and 5th surveys. Comparison of the cross-sectional results from the Know Your Heart study (KYH) and Tromsø Study 7th wave (Tromsø 7) showed that women in KYH had higher levels of adiposity than in Tromsø 7, while levels were similar for men. Despite evidence that adiposity was associated with carotid plaque (presence of plaques and number of plaques), adiposity failed to explain the high burden of carotid plaque in KYH compared to Tromsø 7 in women as well as men. Explanations for the greater carotid plaque burden in Russia must be sought elsewhere, although reducing levels of obesity in Russia and Norway must be a priority for other reasons.