The relationship between selected body fatness indices and the level of blood interleukin-6 in female nursing home residents aged 80+ years without inflammation: A pilot study.

Background: Interleukin-6 (IL-6) production facilitates a shift from acute to chronic inflammation that may induce the development of some diseases and aging. Several studies have suggested that adiposity is closely related to serum IL-6 level, but their authors examined relatively young older adults (aged 60-80 years), so it is not clear whether this association would also occur in people at a more advanced age.

Objective: to assess whether in elderly women without inflammation the widely used anthropometric obesity indices are associated with serum IL-6 level and, if so, to determine the best anthropometric predictor of this inflammatory biomarker.

Methods: The sample consisted of 12 women (85.1 ± 3.9 years; 58.1 ± 8.7 kg; 151.9 ± 6.3 cm), the residents of nursing homes, who did not use anti-inflammatory drugs, statins or diuretics and whose blood C-reactive protein (CRP) concentration was lower than 3 mg/l. To determine CRP and IL-6 concentrations, venous blood samples were collected in the morning in a fasted state. The following anthropometric measurements were made in all participants: body weight, body height, the circumferences of waist, hip and neck. Body fat percentage and visceral fat rating (VFR) were determined by bioelectrical impedance analysis. The measurements were then used to calculate body mass index (BMI), body fat mass index (BFMI), body adiposity index (BAI), the waist-hip ratio (WHR) and the waist-height ratio (WHtR). In the statistical analysis, Pearson's correlation coefficients and stepwise multiple regression analysis with backward elimination were used.

Results: A direct relationship was established between IL-6 and CRP levels (r = 0.639; p < 0.05). Moreover, IL-6 significantly and positively correlated with hip and neck circumferences, BMI, BFMI, and BAI, as well as with VFR (r range 0.597-0.704; p < 0.05). The multiple regression analysis for IL-6 showed that the neck circumference was the only statistically significant independent variable (r = 0.496; p < 0.05; SEE = 0.554 pg/ml).

Conclusions: The results suggest that of all popular indices of adiposity neck circumference is the best predictor of serum IL-6 concentration in the oldest old women without inflammation.