What are the most appropriate obesity measures in older adults concerning health-related quality of life?
Obesity is usually defined by a body mass index (BMI) of 30 kg/m² or more in both the younger and the older population. According to this definition, in Germany, 33% of men and 35% of women aged 60-69 years, and 31% of men and 42% of women aged 70-79 years are obese. The BMI is a useful measure of total body fat in younger adults. But since the ageing process leads to changes in body composition by loss of height and skeletal muscle mass along with a redistribution of body fat towards more visceral fat, other obesity measures may be more appropriate for older adults. Despite existing research comparing different measures of obesity with respect to different outcomes in older individuals, it is still unclear which measure and which cut-point best describes the influence of obesity on health in older adults.
The present study thus compared different obesity measures in their association with health-related quality of life and self-rated physical constitution, two important aspects of healthy and successful ageing, in older adults. Data from 883 participants of the German KORA-Age cohort study (2009-2012), aged 65 years or older, were used. Seven obesity measures, assessed at baseline in 2009 and categorized using the established obesity cut-points for the general adult population, were compared: BMI (the usual measure of obesity), waist circumference (WC), waist-to-hip ratio, waist-to-height ratio, fat mass percentage based on bioelectrical impedance analysis, hypertriglyceridemic waist (a combination of increased WC and elevated serum triglyceride levels) and sarcopenic obesity (a combination of increased body fat and decreased skeletal muscle mass and/or strength). The last two measures are extensions to the current definitions of obesity by considering additional aspects. Quality of life and physical constitution were collected at baseline and at the 3-year follow-up in 2012 with postal questionnaires.
Nearly all obesity measures were significantly inversely associated with both outcomes in the cross-sectional analyses, thus confirming the results from previous studies. The best obesity measure for quality of life was WC, followed by BMI. For physical constitution, the best obesity measures were hypertriglyceridemic waist and BMI, followed closely by WC. In the longitudinal analyses, none of the obesity measures collected at baseline was significantly associated with changes in quality of life or physical constitution over the follow-up period.
WC showed the strongest association with quality of life among the compared obesity measures and was a good measure for physical constitution as well. The measurement of WC in addition to BMI in older adults both in health checks and for research concerning quality of life should thus be supported. As more complex measurement techniques such as bioelectrical impedance analysis do not provide additional information with regard to quality of life, our results suggest that the assessment of simple anthropometric measures is sufficient to determine obesity in older adults in medical practice. In further research, a longer follow-up period or changes in obesity measures between baseline and follow-up should be taken into consideration in longitudinal analyses.
The paper, ‘Comparison of different measures of obesity in their association with health-related quality of life in older adults – results from the KORA-Age study‘ is published in the journal Public Health Nutrition and is freely available until 8th July 2016.
Authors: Anna Riedl, Susanne Vogt, Rolf Holle, Tonia de las Heras Gala, Michael Laxy, Annette Peters and Barbara Thorand