Obesity as an independent influential factor for reduced radial arterial wave reflection in a middle-aged Japanese male population

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This study aimed to examine whether obesity, including abdominal obesity, is an influential factor for radial arterial wave reflection, as expressed by the augmentation index (AI), in middle-aged Japanese men. Radial arterial pressure waveform was measured using automated applanation tonometry in 828 men (mean age: 47+/-5 years) during an annual health examination at a company. Radial AI was calculated from the waveforms. AI appeared to be similar between subjects with and without obesity (body mass index (BMI) >or=25 and <25 kg m(-2), respectively). However, after adjusting for age, height, heart rate, mean blood pressure, low- and high-density lipoprotein cholesterol, fasting plasma glucose, white blood cell count and other potential confounders, AI was significantly lower in subjects with obesity (71.6%, 95% confidence interval (CI); 70.2-73.0%) than in those without (75.2%, 95% CI; 74.4-76.0%, P<0.001). In a multiple linear regression analysis, BMI was negatively associated with AI (beta=-0.20, P<0.001); other factors associated with AI were heart rate (beta=-0.56), mean blood pressure (beta=0.44), height (beta=-0.24), age (beta=0.15), current smoking (beta=0.09), white blood cell count (beta=0.06) and low-density lipoprotein cholesterol (beta=0.06). Similar associations were found when waist circumference (WC, an index of abdominal obesity) was substituted for BMI in the analysis (beta=-0.12, P<0.001). BMI closely correlated with WC (r=0.87), thus suggesting that approximately 76% (a square of 0.87) of BMI can be explained by WC. In conclusion, although it does not have a major impact, obesity, including abdominal obesity, may be an influential factor for reduced radial AI, independently of well-known confounders, in middle-aged Japanese men.