Measuring body composition in overweight individuals by dual energy x-ray absorptiometry

BACKGROUND: Dual energy x-ray absorptiometry (DXA) is widely used for body composition measurements in normal-weight and overweight/obese individuals. The limitations of bone densitometers have been frequently addressed. However, the possible errors in assessing body composition in overweight individuals due to incorrect positioning or limitations of DXA to accurately assess both bone mineral density and body composition in obese individuals have not received much attention and are the focus of this report. DISCUSSION: We discuss proper ways of measuring overweight individuals and point to some studies where that might not have been the case. It appears that currently, the most prudent approach to assess body composition of large individuals who cannot fit under the scanning area would be to estimate regional fat, namely the regions of thigh and/or abdomen. Additionally, using two-half body scans, although time consuming, may provide a relatively accurate measurement of total body fat, however, more studies using this technique are needed to validate it. SUMMARY: Researchers using bone densitometers for body composition measurements need to have an understanding of its limitations in overweight individuals and address them appropriately when interpreting their results. Studies on accuracy and precision in measurements of both bone and soft tissue composition in overweight individuals using available densitometers are needed

Insights into household transmission of SARS-CoV-2 from a population-based serological survey

Understanding the risk of infection from household- and community-exposures and the transmissibility of asymptomatic infections is critical to SARS-CoV-2 control. Limited previous evidence is based primarily on virologic testing, which disproportionately misses mild and asymptomatic infections. Serologic measures are more likely to capture all previously infected individuals. We apply household transmission models to data from a cross-sectional, household-based population serosurvey of 4,534 people ≥5 years from 2,267 households enrolled April-June 2020 in Geneva, Switzerland. We found that the risk of infection from exposure to a single infected household member aged ≥5 years (17.3%,13.7-21.7) was more than three-times that of extra-household exposures over the first pandemic wave (5.1%,4.5-5.8). Young children had a lower risk of infection from household members. Working-age adults had the highest extra-household infection risk. Seropositive asymptomatic household members had 69.4% lower odds (95%CrI,31.8-88.8%) of infecting another household member compared to those reporting symptoms, accounting for 14.5% (95%CrI, 7.2-22.7%) of all household infections

Interaction between vision and neck proprioception in the control of stance

Balance control depends on the interaction of multiple inputs originating from different sensory systems. Here, we investigated the effect on quiet human stance of changing the visual condition prior to a proprioceptive perturbation produced by vibration of dorsal neck muscles. In complete absence of visual references, the amplitude of the postural responses to neck vibration (forward shift of the centre of foot pressure) was the largest and became progressively larger as a function of the repetition of administered stimuli. The posture-destabilizing effect of vibration eyes-closed (EC) and the build-up effect were reduced if vibration was preceded by a period during which vision was allowed (EO). Similarly, the small destabilizing effect of vibration EO was increased if vibration was preceded by an EC period. The fore-period must last more than 3 s in order to affect the response to neck muscle vibration. The responsiveness to a proprioceptive disturbing input does not immediately change on adding or subtracting vision, but a finite time period must elapse before the postural \u201cset\u201d defined by vision is fully established. The findings underline the importance of time when vision is used in re-weighting the excitability of the postural control mechanisms

Interaction between vision and neck proprioception in the control of stance

Balance control depends on the interaction of multiple inputs originating from different sensory systems. Here, we investigated the effect on quiet human stance of changing the visual condition prior to a proprioceptive perturbation produced by vibration of dorsal neck muscles. In complete absence of visual references, the amplitude of the postural responses to neck vibration (forward shift of the centre of foot pressure) was the largest and became progressively larger as a function of the repetition of administered stimuli. The posture-destabilizing effect of vibration eyes-closed (EC) and the build-up effect were reduced if vibration was preceded by a period during which vision was allowed (EO). Similarly, the small destabilizing effect of vibration EO was increased if vibration was preceded by an EC period. The fore-period must last more than 3 s in order to affect the response to neck muscle vibration. The responsiveness to a proprioceptive disturbing input does not immediately change on adding or subtracting vision, but a finite time period must elapse before the postural “set” defined by vision is fully established. The findings underline the importance of time when vision is used in re-weighting the excitability of the postural control mechanisms