Fluctuating asymmetry, a marker of poor growth quality, is associated with adult male metabolic rate

Vitamin D and adolescent idiopathic scoliosis, should we stop the hype? A cross-sectional observational prospective study based on a geometric morphometrics approach

PURPOSE

There is strong evidence supporting the presence of fluctuating asymmetry (FA) in Adolescents with Idiopathic Scoliosis (AIS). Additionally, recent research investigating the relationship between vitamin D and AIS found a relation between them. We hypothesize a negative correlation between FA and vitamin D.

METHODS

We performed a surface scan of the torso of 53 AIS patients, a blood test to measure vitamin D and the radiographic Cobb angle. A correlation analysis between vitamin D and FA was carried out to test our hypothesis, and a regression of vitamin D on 3D shape was performed to observe shape differences between the vitamin D deficiency and insufficiency groups.

RESULTS

There was no correlation between vitamin D and FA. We found a strong negative correlation between vitamin D and the Cobb angle only in the premenarche group (n = 7; r = - 0.92). Differences in shape were observed between the deficiency and insufficiency groups, and that differences were related to the width of the torso, but not the rotation or lateral flexion.

CONCLUSIONS

Our results do not support the massive screening of vitamin D in AIS. Shape analysis revealed differences between the shape of the deficiency and insufficiency groups related to robustness. However, this finding had no relation with the scoliosis characteristics, it just reflected different body composition, and its importance should be explored in future.

Right-left digit ratios, a novel form of asymmetry: Patterns of instability in children and relationships to platelet counts and hospitalization in adults with COVID-19

High right minus left (R-L) asymmetry of digit ratios has been reported to be linked to hospitalization for COVID-19. Here we examined the developmental patterns of this novel form of asymmetry in children and further explored their relationships to platelet counts and hospitalization for COVID-19 in adult patients. We considered ratios calculated from four digits (2D, 3D, 4D, 5D) in: (i) a sample of healthy participants aged 2 years to 18 years (n = 680, 340 males) and (ii) 96 adult patients (42 males) hospitalized for COVID-19 and 100 controls (53 males). The protocol for (ii) included a questionnaire and laboratory test results. In sample (i) of the six unsigned digit ratio asymmetries, those which included 5D had the highest mean asymmetry with the greatest between-individual variation and they were unstable over the age range of 2 years to 18 years. In sample (ii) patients showed higher asymmetries than controls in four ratios (2D:4D, 2D:5D, 3D:5D, 4D:5D) and a sum of asymmetries of the two independent ratios (2D:4D+3D:5D) correlated positively with platelet counts and hospitalization. Conclusion: Means and SDs of digit ratio asymmetry that include the 5th digit are high and age-unstable. Digit ratio asymmetry, particularly 5th digit ratio asymmetry and a composite measure of 2D:4D + 3D:5D asymmetry, may be positively linked to high platelet counts in COVID-19 patients and to an elevated risk of hospitalization.

Formal models for the study of the relationship between fluctuating asymmetry and fitness in humans

OBJECTIVES

To evaluate three of the main verbal models that have been proposed to explain the relationship between fluctuating asymmetry and fitness in humans: the "good genes," the "good development," and the "growth" hypotheses.

MATERIALS AND METHODS

A formal model was generated for each verbal model following three steps. First, based on the literature, a theoretical causal model and the theoretical object of inquiry were outlined. Second, an empirical causal model and the targets of inference were defined using observational data of facial asymmetries and life-history traits related to fitness. Third, generalized linear models and causal inference were used as the estimation strategy.

RESULTS

The results suggest that the theoretical and empirical assumptions of the "good genes" hypothesis should be reformulated. The results were compatible with most of the empirical assumptions of "the good development" hypothesis but suggest that further discussion of its theoretical assumptions is needed. The results were less informative about the "growth" hypothesis, both theoretically and empirically. There was a positive association between facial fluctuating asymmetry and the number of offspring that was not compatible with any of the empirical causal models evaluated.

CONCLUSIONS

Although the three hypotheses focus on different aspects of the link between asymmetry and fitness, their overlap opens the possibility of a unified theory on the subject. The results of this study make explicit which assumptions need to be updated and discussed, facilitating the advancement of this area of research. Overall, this study elucidates the potential benefit of using formal models for theory revision and development.

Anthropometric fluctuating asymmetries in living humans through the eyes of an anthropologist

There are many environmental and genetic factors that disrupt the stable structure of development in organisms. Although the strength of these vary, they leave certain signs in the body structure. Fluctuating asymmetry is a widely used population-level index of developmental instability, developmental noise, and robustness. Many bilateral traits are used in fluctuating asymmetry studies in humans. These traits include dermatoglyphics, limb lengths and widths, bilateral facial characters, and teeth. In this review, I evaluate the measurement methods of many bilateral anthropometric characters, taken from the bodies of living individuals with classical digital calipers.