The effects of sex, nation, ethnicity, age and self-reported pubertal development on participant-measured right-left 2D:4D (Dr-l) in the BBC internet study.

Digit ratio (2D:4D) - a proxy for prenatal sex steroids - shows sex, nationality and ethnic differences and is linked to pubertal onset. It is unclear whether right-left 2D:4D (Dr-l) also correlates with prenatal sex steroids, as evidence of these differences has been less conclusive. The present study examined the effects of sex, nation, ethnicity, age and self-reported pubertal development (i.e. the rate of physical development and age at menarche [females] or first shave [males]) on Dr-l in a large online study (the BBC internet study). Digit lengths were self-measured in 201,865 adults (110,955 males) and the sample of nations included 41 countries. Participants reported the self-perceived rate of physical pubertal development on a five-point scale (from very slow to very fast) and provided information on the age at menarche or first shave. Adult (>17 years) males had lower Dr-l than females with weak effect size across 41 nations (males-females; d = -.065, p < .0001). There were sex and ethnicity effects on Dr-l across seven ethnic groups with males < females and lower Dr-l in Whites and Middle/Near Eastern participants compared to Asian, Black and Chinese respondents. Considering age effects, the authors focused on participants >12 years; there were stable sex differences and a weak positive effect of age on Dr-l. Dr-l showed a positive relationship with the rate of physical development and a negative relationship with age at menarche or first shave. Relationships were present in males and females with stronger effects in the latter. It is concluded that Dr-l shows a weak sex difference (males < females) independent of nation, ethnicity and age, and suggest that Dr-l is a proxy for prenatal sex steroids.

Digit ratios and their asymmetries as risk factors of developmental instability and hospitalization for COVID-19.

COVID-19 presents with mild symptoms in the majority of patients but in a minority it progresses to acute illness and hospitalization. Here we consider whether markers for prenatal sex hormones and postnatal stressors on developmental instability, i.e. digit ratios and their directional and unsigned asymmetries, are predictive of hospitalization. We focus on six ratios: 2D:3D; 2D:4D; 2D:5D; 3D:4D; 3D:5D; 4D:5D and compare hospitalized patient and control means for right, and left ratios, directional asymmetries (right-left) and unsigned asymmetries [|(right-left)|]. There were 54 patients and 100 controls. We found (i) patients differed in their digit ratios from controls (patients > controls) in all three ratios that included 5D (2D:5D, 3D:5D and 4D:5D) with small to medium effect sizes (d = 0.3 to 0.64), (ii) they did not differ in their directional asymmetries, and (iii) patients had greater |(right-left)| asymmetry than controls for 2D:4D (d = .74) , and all ratios that included 5D; 2D:5D (d = 0.66), 3D:5D (d = .79), 4D:5D (d = 0.47). The Composite Asymmetry of the two largest effects (2D:4D + 3D:5D) gave a patient and control difference with effect size d = 1.04. All patient versus control differences were independent of sex. We conclude that digit ratio patterns differ between patients and controls and this was most evident in ratios that included 5D. Large |(right-left)| asymmetries in the patients are likely to be a marker for postnatal stressors resulting in developmental perturbations and for potential severity of COVID-19.

Risk factors of striae gravidarum.

BACKGROUND: Stretch marks are a common skin disorder. Pregnancy-related lesions are defined as striae gravidarum. The root cause of striae formation remains unknown. OBJECTIVE: The aim of this paper was to identify the risk factors associated with striae gravidarum (SG) development. PATIENTS AND METHODS: The study was conducted at Plastic, Reconstructive and Aesthetic Surgery Clinic and Obstetrics Outpatient Department among 299 Caucasian women maximum 6 months after the delivery, regardless of whether they were primiparas or multiparas. RESULTS: Among the women participating in the study, 71.2% (213 of 299) developed striae gravidarum at least in one site. Logistic regression analysis showed that four of the analysed factors were independent predictors of striae gravidarum occurrence: family history of SG, BMI before pregnancy, the lack of chronic diseases and birthweight (P < 0.0001). It has been found that the presence of striae distensae on the breasts increases the risk of SG development (71.4% vs. 28.6%, P = 0.0008), whereas the presence of these lesions on the thighs decreases the risk (23% vs. 77%, P = 0.0076). CONCLUSION: In this study, we presented a model that can help to predict the risk of SG formation, including family history of SG, BMI before pregnancy, birthweight and chronic diseases. Moreover, women with stretch marks on their breasts should know that the risk of SG development is significantly higher, whereas lesions on the thighs do not increase such a risk.