Association of the 2D:4D digit ratio with body composition among the Polish children aged 6-13 years

An Exploratory Analysis on the 2D:4D Digit Ratio and Its Relationship with Social Responsiveness in Adults with Prader-Willi Syndrome

Prader-Willi syndrome (PWS) is a genetic disorder produced by a lack of expression of paternally derived genes in the 15q11-13 region. Research has generally focused on its genetic and behavioral expression, but only a few studies have examined epigenetic influences. Prenatal testosterone or the maternal testosterone-to-estradiol ratio (MaTtEr) has been suggested to play an important role in the development of the 'social brain' during pregnancy. Some studies propose the 2D:4D digit ratio of the hand as an indirect MaTtEr measure. The relationship between social performance and MaTtEr has been studied in other neurodevelopmental conditions such as Autism Spectrum Disorder (ASD), but to our best knowledge, it has never been studied in PWS. Therefore, our study aims to clarify the possible existence of a relationship between social performance-as measured using the Social Responsiveness Scale (SRS)-and MaTtEr levels using the 2D:4D ratio. We found that, as a group, PWS individuals have shorter index and ring fingers than the control group, but no significant difference in the 2D:4D ratios. The 2D:4D ratio showed a correlation only with Restricted Interests and Repetitive Behavior Subscale, where a positive correlation only for male individuals with PWS was found. Considering only PWS with previous GH treatment during childhood/adolescence (PWS-GH), index and ring fingers did not show differences in length with the control group, but the 2D:4D ratio was significantly higher in the right or dominant hand compared to controls.

The association of prenatal amniotic sex hormones and digit ratio (2D:4D) in children aged 5 to 70 months: A longitudinal study

The sex difference of the 2D:4D digit ratio (female > male)-a proposed marker for prenatal testosterone exposure-is well established. Studies suggest it already exists in utero and is of moderate effect size in adulthood. However, evidence for the claim that 2D:4D reflects prenatal androgen action is limited, and the sex difference may exhibit lability during childhood. In the present study, 244 mothers were recruited in the course of an amniocentesis examination (performed between gestational weeks 14 and 18). Prenatal testosterone (T) and estradiol (E) levels were determined from amniotic fluid for boys and girls. The majority (97.4%, n = 114) of available female T levels (n = 117) were found below the level of quantification. Therefore, only male amniotic fluid data (n = 117) could be included for the analysis of associations between amniotic sex hormones (T levels and T to E ratio (T/E)) and 2D:4D. The families were then invited to each of the five consecutive follow-ups (ages: 5, 9, 20, 40, and 70 months) where children's 2D:4D was measured for both hands. The alternative marker D[r-l] reflects the directional asymmetry of 2D:4D (right subtracted by left 2D:4D) and was subsequently calculated as an additional measure for prenatal T exposure. No significant correlations between amniotic T or the T/E ratio (measured between week 14 and 18 of gestation) with 2D:4D respectively D[r-l] were observed for any time point. There was a significant sex difference (females > males) and a significant age effect with moderate correlations of 2D:4D between time points. 2D:4D increased between 20 and 40 months and between 40 and 70 months of age. The findings raise questions regarding the applicability of 2D:4D as a marker for prenatal androgen action and are discussed in terms of the reliability of obtained digit ratio data as well as in terms of the developmental timing of amniocentesis.

Maternal Age and Behavior during Pregnancy Affect the 2D:4D Digit Ratio in Polish Children Aged 6–13 Years

Background: The length of the second and fourth finger calculated as a ratio (2D:4D) is a marker of prenatal exposure to sex hormones. Higher exposure to testosterone is related to a lower 2D:4D digit ratio, and inversely, higher exposure to estrogen is related to a higher 2D:4D. The digit ratio in humans (prenatally determined by sex hormone levels and androgen receptor activity) is associated with multiple biological, cognitive, and behavioral traits, as well as health in later life. The aim of this study was to verify if maternal traits during pregnancy are associated with 2D:4D among their children. Methods: We investigated 537 boys, 646 girls, and their mothers. The investigation consisted of a questionnaire and a measurement part. In the questionnaire, we included questions about maternal traits during pregnancy such as: illnesses, active and passive smoking, work activity, psychological trauma (death or serious illness of a loved one, divorce, job loss), and age. We performed length measurements of the second and fourth fingers on both hands for both study groups. Results: The GLM analysis showed that children of smoking mothers were characterized by a higher 2D:4D R as compared to their peers whose mothers did not smoke (β = 0.10, p = 0.0008). In turn, the offspring of women who worked during pregnancy exhibited lower 2D:4D R values than the children of women who did not work (β = −0.07, p = 0.0233). It should be noted, however, that the effects of those maternal factors were small, as each of them explained less than 1% of 2D:4D R in the population, adjusted for child age and sex. Pearson’s linear correlation revealed that maternal age was negatively correlated with 2D:4D R in daughters (r = −0.11, p = 0.0137), but not in sons (r = 0.02, p = 0.6908). The negative correlation of 2D:4D R with maternal age indicates that the daughters of older mothers exhibited lower values of that ratio relative to the same-age daughters of younger mothers. Conclusions: For both study groups, the right-hand digit ratio was positively correlated with maternal smoking and negatively with maternal work during pregnancy. Maternal age during pregnancy was negatively related to right hand 2D:4D only among girls.

The 2D:4D index is associated with the development of excess body weight in adults, but not with the rate of weight loss following bariatric surgery

2D:4D finger length ratio is a proxy of prenatal sex hormone exposure. Prenatal testosterone decreases and prenatal estrogens increase this index. In the current study we investigated whether the 2D:4D index, as a marker of the prenatal hormonal environment, is associated with the development of overweight and obesity in adults, and whether is it correlated with the rate of weight loss in patients after bariatric surgery. We tested 125 adults with obesity (BMI ≥ 30.0 kg/m²), 125 adults with overweight (BMI 25.0–29.9 kg/m²) and 153 persons with normal body weight (BMI < 25 kg/m²) of both sexes. We have found that the development of excessive body weight in men and women, and fat accumulation in the upper arms, thighs and lower legs in women with obesity (but not men) are associated with increased prenatal estrogen exposure. This relationship indicates a new area of activity in the field of obesity prevention. Moreover, it seems that the 2D:4D index (especially of the right hand) may be a useful factor in early prediction of the risk of developing excessive body weight in humans. The rate of weight loss after bariatric surgery is independent of prenatal exposure to sex hormones.

Understanding the Associations of Prenatal Androgen Exposure on Sleep Physiology, Circadian Proteins, Anthropometric Parameters, Hormonal Factors, Quality of Life, and Sex Among Healthy Young Adults: Protocol for an International, Multicenter Study

Background

The ratio of the second finger length to the fourth finger length (2D:4D ratio) is considered to be negatively correlated with prenatal androgen exposure (PAE) and positively correlated with prenatal estrogen. Coincidentally, various brain regions are sensitive to PAE, and their functions in adults may be influenced by the prenatal actions of sex hormones.

Objective

This study aims to assess the relationship between PAE (indicated by the 2D:4D ratio) and various physiological (sex hormone levels and sleep-wake parameters), psychological (mental health), and sexual parameters in healthy young adults.

Methods

This study consists of two phases. In phase 1, we will conduct a survey-based study and anthropometric assessments (including 2D:4D ratio and BMI) in healthy young adults. Using validated questionnaires, we will collect self-reported data on sleep quality, sexual function, sleep chronotype, anxiety, and depressive symptoms. In phase 2, a subsample of phase 1 will undergo polysomnography and physiological and genetic assessments. Sleep architecture data will be obtained using portable polysomnography. The levels of testosterone, estradiol, progesterone, luteinizing hormone, follicle-stimulating hormone, prolactin, melatonin, and circadian regulatory proteins (circadian locomotor output cycles kaput [CLOCK], timeless [TIM], and period [PER]) and the expression levels of some miRNAs will be measured using blood samples. The rest and activity cycle will be monitored using actigraphy for a 7-day period.

Results

In Poland, 720 participants were recruited for phase 1. Among these, 140 completed anthropometric measurements. In addition, 25 participants joined and completed phase 2 data collection. Recruitment from other sites will follow.

Conclusions

Findings from our study may help to better understand the plausible role of PAE in sleep physiology, mental health, and sexual quality of life in young adults.

International Registered Report Identifier (IRRID)

DERR1-10.2196/29199

Association of prenatal sex steroid exposure estimated by the digit ratio (2D:4D) with birth weight, BMI and muscle strength in 6- to 13-year-old Polish children

Objectives

The aim of this paper was to provide evidence for the impact of prenatal sex steroid exposure on prenatal and postnatal body size parameters, and muscle strength in children.

Methods

The following anthropometric data were studied in a group of 1148 children (536 boys and 612 girls) aged 6–13 years: the 2D:4D digit ratio, birth weight and length, and birth head and chest circumference. Postnatal parameters (6–13 years) included body weight and height, BMI, waist and hip circumference, WHR, as well as grip strength in both hands. All parameters that required it were adjusted for sex and gestational or chronological age. A general linear model, Pearson’s correlation, t-statistics and Cohen’s Δ were used in statistical analysis.

Results

Among birth size parameters, only birth weight was significantly negatively correlated with the 2D:4D digit ratio in children. Higher (feminized) digit ratios were significantly correlated with postnatal parameters such as body weight, BMI, and waist and hip circumference (positively), as well as hand grip strength–a proxy for muscular strength (negatively).

Conclusion

Problems with maintaining adequate body size parameters and muscle strength may be programmed in fetal life and predicted on the basis of the 2D:4D digit ratio. Body weight at birth and in early ontogenesis are additive correlates of the 2D:4D ratio. The present findings suggest that the 2D:4D digit ratio is related to postnatal phenotypes such as birth weight, overweight, and obesity as well as muscle strength in 6–13-year-old children of both sexes.

Thyroid diseases and second to fourth digit ratio in Polish adults

The association between second to fourth finger ratio and thyroid diseases is unexplained. There is a possible interaction between prenatal exposition to sex hormone and thyroid functions in the adulthood. The study included 175 adults investigated in Łódź in the central Poland. It consisted of two main parts: a survey including questions about occurrence of thyroid gland dysfunction and anthropometric measurements (body mass and height and length of the second and fourth finger, waist and hip circumferences). The women who had thyroid disease had higher 2D:4D digit ratio (left hand) (mean = 1.004; SD = 0.036) than healthy ones (mean = 0.989; SD = 0.030) (t = − 2105; p = 0.038; d = 0.707). The association between thyroid diseases occurrence and prenatal steroid hormone exposition is noticed. Only females who had thyroid diseases tend to have higher 2D:4D digit ratio, for left hand.

Cortisol concentration affects fat and muscle mass among Polish children aged 6-13 years

Background

Cortisol is a steroid hormone acting as a stress hormone, which is crucial in regulating homeostasis. Previous studies have linked cortisol concentration to body mass and body composition.

Methods

The investigations were carried out in 2016–2017. A total of 176 children aged 6–13 years in primary schools in central Poland were investigated. Three types of measurements were performed: anthropometric (body weight and height, waist and hip circumferences), body composition (fat mass FM (%), muscle mass – MM (%), body cellular mass - BCM (%), total body water - TBW (%)), and cortisol concentration using saliva of the investigated individuals. Information about standard of living, type of feeding after birth, parental education and maternal trauma during pregnancy was obtained with questionnaires.

Results

The results of regression models after removing the environmental factors (parental education, standard of living, type of feeding after birth, and maternal trauma during pregnancy) indicate a statistically significant association between the cortisol concentration and fat mass and muscle mass. The cortisol concentration was negatively associated with FM (%) (Beta=-0.171; p = 0.026), explaining 2.32 % of the fat mass variability and positively associated with MM (%) (Beta = 0.192; p = 0.012) explaining 3.09 % of the muscle mass variability.

Conclusions

Cortisol concentration affects fat and muscle mass among Polish children.

Trial registration

The Ethical Commission at the University of Lodz (nr 19/KBBN-UŁ/II/2016).

Supplementary Information

The online version contains supplementary material available at 10.1186/s12887-021-02837-3.

Associations between second to fourth digit ratio, cortisol, vitamin D, and body composition among Polish children

Associations between body characteristics (body composition: fat mass, muscle mass, cell, and water mass as well as body proportion—BMI), the 2D:4D digit ratio, and the concentrations of cortisol and vitamin (25-OH)D among Polish children have not been studied before. A total of 133 (73 girls and 60 boys) healthy Polish children aged 7–11 years were examined. The investigation was divided into three parts: measuring (the length of the second and fourth fingers in both hands, body composition, and body height and mass), questionnaires (socioeconomic status), and laboratory investigations (25-OH vitamin D and cortisol concentrations in saliva measured with ELISA methods). Boys with digit ratios below 1 had lower vitamin D concentration than those with digit ratios equal to or higher than 1 (Z = − 2.33; p = 0.019). Only boys with the male-typical pattern of 2D:4D digit ratio tended to have a lower 25-OH vitamin D concentration in saliva. Thus, it might indicate an effect of prenatal programming on the concentrations of steroid hormones in later life. Neither vitamin D, 2D:4D digit ratio nor the cortisol level was associated with the body components or proportions. More studies are needed to evaluate the molecular and genetic background of this phenomenon.

Association patterns between 2D:4D ratio and age at menarche: the impact of methodology

The ratio of index finger to ring finger length (2D:4D) is a sexually dimorphic feature and widely used as an indicator of prenatal androgen-estrogen exposure. Several studies have investigated the relationship between the 2D:4D ratio and the onset of the first menstrual period (menarche) in women.

The present study tested the association patterns between 2D:4D ratio and age at menarche. Furthermore, the impact of methods of measuring finger lengths was considered.

Two samples were used to conduct the study. One sample consisted of 110 women who self-measured their finger lengths. The finger length measurements in the second sample (88 women) were taken from one trained observer using the caliper-based technique. Age at menarche was determined using a retrospective method.

Women from the first sample reported an average age for the onset of the first menstrual bleeding at 12.9 (SD = 1.4) years of age. There was no significant association between the left and right 2D:4D ratio and the age at menarche. The second sample showed a mean age at menarche at 12.8 (SD = 1.3) years of age. Here, the right hand 2D:4D ratio and age at menarche were significantly correlated (p<0.001).

A more feminine 2D:4D ratio was significantly associated with an earlier menarcheal age only in the sample with direct finger length measurements by a trained investigator. The sample using self-measurements yielded no significant associations between menarcheal age and 2D:4D. The use of a reliable and well-founded methodology is essential for obtaining meaningful results.

Association of saliva 25(OH)D concentration with body composition and proportion among pre-pubertal and pubertal Polish children

OBJECTIVES

Due to increasing problems with obesity and vitamin D deficiency among children, studies that tackle both problems together are needed.

METHODS

Data were collected from 182 randomly selected children aged 6-13 years in primary schools in central Poland. Measures included anthropometric dimensions, body composition, questionnaires completed by participants' parents, and saliva samples. The level of 25(OH)D was assessed from the saliva samples using an enzyme-linked immunosorbent assay kit. The children were divided into two groups: pre-pubertal (girls below 10 years and boys below 11 years) and pubertal individuals (girls above 10 years and boys above 11 years).

RESULTS

The 25(OH)D concentrations were higher in late spring (June) among pre-pubertal children than in the autumn (November-December) among pubertal children. The level of 25(OH)D was positively correlated with body cell mass (BCM,%) among all children (pubertal: R = 0.20, P = .044; pre-pubertal: R = 0.23, P = .041) and inversely associated with waist-to-hip ratio (WHR) among pubertal children of both sexes (R = -0.25; P = .031). The stepwise regression analysis revealed that investigation in spring (June) and breastfeeding was associated with increased muscle mass (MM, %) (beta = 0.253, P = .003 and beta = 0.225, P = .005, respectively) and total body water (TBW, %) (beta = 0.276, P = .004 and beta = 0.246, P = .011, respectively) and was associated with decreased body mass index (BMI; beta = -0.222, P = .024 and beta = -0.269, P = .009, respectively) and fat mass (%) (beta = -0.288, P = .003 and beta = -0.266, P = .005, respectively).

CONCLUSIONS

Season of salivary sampling and breastfeeding status were more strongly associated with body components, BMI and WHR, than 25(OH)D concentrations.

Digit ratios and motor and health-related fitness in pre-adolescent females

Background: Assessing different aspects of physical fitness in children whose abilities are undeveloped and their associations with second-to-fourth digit ratio (2D:4D) may better determine the potential athleticism of an individual.Aim: The purpose of the study was to examine relationships between the digit ratios and selected motor and health-related fitness parameters in a large sample of pre-adolescent females.Subjects and methods: Participants included 8-12 year old Iranian and Afghan girls. The length of the left and right second and fourth digits was measured by scanning and computer-assisted image analysis. Motor- and health-related fitness tests were evaluated.Results: No significant correlations were noted between right 2D:4D ratio and physical fitness components. Left 2D:4D and physical fitness components were not correlated, with the exception of handgrip strength (r = -0.193). However, right and left second digit lengths were negatively correlated with predicted VO_2max (p ≤ 0.01). In addition, right-left 2D:4D was significantly negatively correlated with flexibility, and significantly positively correlated with height and body fat percentage.Conclusion: In contrast to previous investigations, it seems that left 2D:4D is a predictor of strength, but not aerobic exercise. It is suggested there may be a potential relationship between prenatal androgen exposure and high flexibility, low body fat percentage and the generation of muscular strength in pre-adolescent females.

Sex differences in relationship between body composition and digit length ratio (2D:4D) in students of military courses

It is believed that the second to fourth finger length ratio is an indirect indicator of fetal testosterone levels. It is pointed out that there is a relationship between the 2nd to 4th finger length ratio and the body structure in women and men. Studies on the relationship between body composition and 2D:4D finger length among military students have not been carried out so far. The work aims to determine the dependence of body composition and the quotient of the 2nd and 4th fingers length of military students. The research material has been gathered as a result of examinations of women and men studying military subjects. The study involved 55 women and 65 men. The tests included anthropometric measurements (body height, body weight, length of the second and the fourth fingers) and body composition measurements. As a result of the tests, no dimorphic differentiations in the digit length ratio (2D:4D) was indicated. The BMI, muscle mass, lean body mass and water in the body demonstrated higher values in men than in women. However, the fat content in men was low. It was found that the relationship exists between muscle mass, lean mass and total water content in the body and the 2D:4D finger length ratio in the left hand in women. A higher level of fetal testosterone, characterized by lower values of the 2nd to 4th finger length ratio, may be associated with a higher content of muscle mass, lean body mass and water in the body of adult women leading a similar lifestyle.