Abstract 

Background: Body composition is an important health parameter in several disease conditions, e.g., the inflammatory back disease spondylarthritis (SpA). Body mass index (BMI) is the most common anthropometric body composition assessment but has several limitations. As a result, several studies have been carried out to improve its validity by combining different body parameters. Nickerson equation (NE) is one of the equations developed to address the limitation of BMI. However, the knowledge is lacking on the preference of the NE which includes BMI (body weight and height), hand grip strength, and sex to estimate body fat percent over BMI alone among individuals with spondylarthritis.

Aim: This study aims to assess the association between BMI and the Nickerson equation (NE) -estimate body fat percentage- with body composition measured with bioelectrical impedance assessment (BIA) and in individuals with spondylarthritis.

Methods: Thirty-two individuals with SpA 17 women and 15 men with a median (range) age of 47 (30-66) years were included. The weight (kg), length (cm), hand grip strength (kg), and sex were registered to estimate values of body composition by the NE. BIA was equally used to assess total body fat %, visceral fat (cm2), and skeletal muscle mass (kg). Associations between the NE, or body mass index (BMI), and BIA were analyzed by Spearman’s correlations (rs).

Results: The result shows that the NE has a rs of 0.6 to BIA total body fat higher than the BMI correlation coefficient of 0.3 but NE has a lower coefficient of 0.3 to visceral fat than the BMI which is 0.6, NE also has a negative correlation coefficient of 0.6 to skeletal muscles. 

Conclusion: This study suggested that the Nickerson Equation which combines BMI, hand grip strength, and sex is a better assessment of body composition in individuals with spondylarthritis and encourages clinicians to consider using the Nickerson equation in clinical setting instead of BMI where access to precise assessment tools is unavailable.