The 2nd–4th digit ratio (2D:4D) and neck circumference: implications for risk factors in coronary heart disease

Sexual Dimorphism and Sex-2D : 4D Interactions on Fasting Lipid Variables in an Adult Ghanaian Population

Prenatal hormone exposure has been suggested as a correlate of adult circulating estrogen and testosterone. If this observation is true, then prenatal hormone exposure may have an association with lipid homeostasis in adulthood. The study sought to investigate sexual dimorphism and the interactions between the putative marker of prenatal hormone exposure (2D : 4D) and sex on adult fasting plasma lipid variables. The study was cross-sectional from June to December 2021 at the University for Development Studies. The participants were between 18 and 30 years of age and consisted of 206 healthy persons (female = 93, male = 113). The right hand (2D : 4DR), the left hand (2D : 4DL), and the right-left 2D : 4D difference (Dr-l) were measured using computer-assisted analysis. Fasting venous blood samples were collected and analyzed for lipid variables including total cholesterol (TCHOL) and high-density lipoprotein cholesterol (HDL-C). There were no significant differences in the 2D : 4D ratio and lipid variables between males and females. However, after adjusting for age and BMI, the 2D : 4DR (P = 0.014) and the 2D : 4DL (P = 0.007) increased with increasing fasting plasma HDL-C on average. Moreover, there were significant interactions between sex and the 2D : 4DR (P = 0.002) and also, the 2D : 4DL (P = 0.005) on fasting plasma HDL-C. The relationship between HDL-C and the 2D : 4D ratio was positive in females but negative in males. The 2D : 4DR accounted for about 54.9% and 46.0% while the 2D : 4DL accounted for about 48.2% and 14.0% of the variabilities in fasting plasma HDL-C in females and males, respectively. Prenatal hormone exposure may partly account for the sexual dimorphism in adult lipid homeostasis.

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.

The relationship between 2D:4D ratio and postpartum adult female variables in a Ghanaian population

OBJECTIVES

Postpartum hematological and anthropometric assessment is a requirement for optimal maternal and child health. The study aimed to determine the relationship between the 2D:4D ratio and postpartum hematological and anthropometric variables in adult females.

METHODS

The study was cross-sectional from December 2020 to April 2021 involving 272 postpartum adult females, aged between 18 and 36 years. The right (2D:4DR) and the left (2D:4DL) digit ratios were measured using computer-assisted analysis. Fasting venous samples were collected at a median (interquartile range) of 111 (44-210) days postpartum and analyzed for total testosterone (TT), estradiol, sex hormone-binding globulin, and complete blood count.

RESULTS

The mean ± standard deviation 2D:4DR and 2D:4DL were 0.94 ± 0.04 and 0.93 ± 0.04, respectively. As expected, the TT (r = -0.198, p = .015) and the free androgen index (FAI: r = -0.186, p = .019) were inversely correlated with the 2D:4DL while free testosterone (FT%: r = -0.157, p = .038) was inversely correlated with the 2D:4DR. The absolute basophile count (BASO: r = -0.124, p = .040) and the Platelet-lymphocyte ratio (PLR: r = -0.153, p = .016) were inversely correlated with the 2D:4DL and the 2D:4DR respectively. In addition, the mean cell volume was inversely correlated with the 2D:4DR (r = -0.139, p = .024) and the 2D:4DL (r = -0.122, p = .045). Moreover, the 2D:4DR was inversely correlated with height (r = -0.164, p = .007). Unexpectedly, the red blood cell count (RBC: r = 0.138, p = .025) was positively correlated with the 2D:4DR.

CONCLUSION

There are significant relationships between the 2D:4D ratio and postpartum female variables. These findings are useful preliminary reference data for postpartum research and subsequent 2D:4D ratio studies.

The relationship between digit ratio (2D:4D) and muscular fitness: A systematic review and meta-analysis

BACKGROUND

Digit ratio (2D:4D), a marker of prenatal testosterone exposure, is a weak negative correlate of sports/athletic/fitness performance. While numerous studies have examined the relationship between 2D:4D and physical fitness, there has never been a comprehensive study that has synthesized studies examining relationships between 2D:4D and muscular fitness.

OBJECTIVES

To systematically review and meta-analyze the relationship between 2D:4D and muscular fitness measured as handgrip strength (HGS).

METHODS

We systematically searched five electronic databases, reference lists, topical systematic reviews/meta-analyses, and personal libraries in November 2020. Peer-reviewed, cross-sectional studies that reported Pearson's correlation coefficients between objectively measured 2D:4D and HGS were included. We used random-effects meta-analysis to estimate the pooled correlation and the 95% confidence interval (95%CI), and moderator analyses to estimate the influence of sex and age.

RESULTS

Data from 22 studies, representing 5271 individuals from 11 countries ranging in (mean) age from 10.4 to 58.0 years, were included. Overall, there was a weak negative correlation between 2D:4D and HGS (r = -0.15, 95%CI = -0.20 to -0.09), indicating that individuals with low 2D:4Ds had high HGS. We found substantial heterogeneity between studies (Q = 123.4, p < .0001; I²  = 74%), but neither sex (Q = 0.003, p = .96) nor age (Q = 0.46, p = .50) significantly moderated the pooled correlation.

CONCLUSIONS

We found a weak negative relationship between 2D:4D and HGS, which showed substantial heterogeneity between studies, but was neither moderated by sex nor age. Our finding probably reflects both the long-term (organizational) and short-term (activational) benefits of testosterone.

Second-to-Fourth Digit Ratio (2D:4D) in Psychiatric Disorders: A Systematic Review of Case-control Studies

The second-to-fourth digit ratio (2D:4D) is an indirect, retrospective, non-invasive measure that correlates negatively with intrauterine exposure to testosterone. The present meta-analysis aimed to evaluate if 2D:4D differs between patients with psychiatric disorders and controls. In September 2019, we searched in Web of Knowledge, PsycINFO, Embase, and CINHAL, and retrieved 619 papers. We finally included 43 case-control studies which compared the 2D:4D ratio of patients with autism spectrum disorder (ASD) (n = 16), schizophrenia (n = 8), gender non-conformity (n = 7), addictions (n = 5), attention deficit-hyperactivity disorder (ADHD) (n = 4), mood disorders (n = 2), and intellectual disability (n = 1) to non-clinical controls. Meta-analyses showed that, overall, psychiatric patients had lower 2D:4D than healthy controls (n = 43, overall sample = 9,484, mean difference = -0.0056, 95% confidence interval from -0.0093 to -0.002, I2 = 74%), with more pronounced differences in the right hand, males, and children. Considering psychiatric disorders individually, significant differences were found in the ASD, ADHD, and addictions groups, in which 2D:4D was significantly lower than healthy controls. Conversely, the right hand of males with schizophrenia showed higher 2D:4D than healthy controls. No other significant differences were detected. Although our results need to be cautiously interpreted and find limited applications in clinical practice, they may suggest that 2D:4D is altered in some psychopathological conditions, underlining the role of prenatal exposure to sex steroids in the etiology of psychiatric disorders.

Parental income inequality and children's digit ratio (2D:4D): a 'Trivers-Willard' effect on prenatal androgenization?

Income inequality is associated positively with disease prevalence and mortality. Digit ratio (2D:4D) - a negative proxy for prenatal testosterone and a positive correlate of prenatal oestrogen - is related to several diseases. This study examined the association of income inequality (operationalized as relative parental income) and children's 2D:4D. Participants self-measured finger lengths (2D=index finger, and 4D=ring finger) in a large online survey conducted in July 2005 (the BBC Internet Study) and reported their parents' income. Children of parents of above-average income had low 2D:4D (high prenatal testosterone, low prenatal oestrogen) while the children of parents of below-average income had high 2D:4D (low prenatal testosterone, high prenatal oestrogen). The effects were significant in the total sample, present among Whites (the largest group in the sample), in the two largest national samples (UK and USA) and were greater for males than females. The findings suggest a Trivers-Willard effect, such that high-income women may prenatally masculinize their sons at the expense of the fitness of their daughters. Women with low income may prenatally feminize their daughters at the fitness expense of their sons. The effect could, in part, explain associations between low income, high 2D:4D (low prenatal testosterone) and some major causes of mortality such as cardiovascular disease.

Association between the 2d:4d and cardiovascular risk factors: Body mass index, blood pressure and body fat

OBJECTIVES

To examine the relationship between the cardiovascular risk factors such as obesity as measured by Body mass index (BMI), body fat and blood pressure with the second to fourth digit ratio (2d:4d); a prenatal testosterone exposure marker.

METHODS

The 2d:4d for both hands were measured for the Indian male subjects' (n = 1217). Subject's anthropometric parameters such as height, weight, skinfold thicknesses at various regions and blood pressure measurements were collected in a cross-sectional study with a convenient sampling approach. The association between digit ratio and the other variables were examined using analysis of variance, Pearson's correlation test and linear regression methods.

RESULTS

The study included 1193 subjects and all were males aged 19.69 ± 5.38 years (range 13 to 40 years). The subjects' body mass index (BMI) was 19.45 ± 3.82 and right and left hand 2d:4d were 0.958 ± 0.054, and 0.958 ± 0.061 respectively. The systolic blood pressure (SBP) and BMI significantly differed between the higher and lower half of right 2d:4d. The left hand 2d:4d was significantly correlated with SBP (r = 0.075, p = 0.028) and significantly differed between different hypertensive groups (p < 0.003, F = 3.552, df = 5).

CONCLUSION

The study observed an association between 2d:4d with hypertension and BMI among young Indian population, emphasizing the effect of prenatal testosterone on late life cardiovascular risk factor.

Digit ratio (2D:4D) is not related to cardiovascular diseases or their risk factors in menopausal women

OBJECTIVES

Digit ratio (2D:4D) is widely used as a biomarker of prenatal hormonal environment linked to the growing number of adult health and disease-related characteristics. It has been suggested that 2D:4D is a good predictor of cardiovascular diseases (CVD) risk among men, but results in women are still inconclusive. Here we test the relationship between 2D:4D and the incidence of cardiovascular diseases (CVD), and their risk factors in Polish, rural women.

METHODS

The participants were 410 women age 50 and older. Structured questionnaire was used to gather personal and medical data, including the history of CVD diagnosed by a medical doctor. Anthropometric measurements of body height, weight, and finger lengths were performed. Right-hand and left-hand 2D:4D, mean 2D:4D, D_l-r , and BMI were calculated afterward. For a subgroup of participants (n = 329) fasting blood sample was collected (in order to assess the lipid profile and glucose levels) and blood pressure was measured. Age, education level and BMI were included as potential covariates.

RESULTS

No statistically significant association was observed between 2D:4D markers and the incidence of CVD (eg, heart attack, stroke) or CVD risk factors (dyslipidaemia, dysglycaemia or hypertension), when controlled for age, education and BMI.

CONCLUSIONS

The results of our study add to the growing number of studies investigating the sex-difference of the association between 2D:4D and cardiac health. We conclude that from a public health perspective 2D:4D may not be a valuable biomarker of elevated risk of CVDs in women.

Radiographic digit ratios (2D:4D) of Afro-Caribbean children: Comparisons with published data from white children

BACKGROUND

Digit ratio (2D:4D) from soft-tissue measurements of fingers from children and adults from Black and White ethnic groups show sex differences (males<females) and group differences (Black< White). However, less is known about such differences in radiographic 2D:4D.

AIM

To consider sex and ethnic differences in radiographic 2D:4D of children of Afro-Caribbean descent and to compare these means with "standards" from White children.

SUBJECTS AND METHODS

A cross-sectional design with samples from Afro-Caribbean children aged 6 to 11 years compared to published radiographic measurements for White children in the Fels Longitudinal Study.

RESULTS

Radiographic 2D:4D showed ethnic differences such that Afro-Caribbeans<Whites. There was an age-stable right-side sex difference (boys<girls) in the 2D:4D of the distal phalanx and the distal soft-tissue tip in the Afro-Caribbean children but not in the proximal- and middle-phalanges or the composite length of the phalanges. Sex differences in 2D:4D (boys<girls) were present in the White children in the middle and proximal phalanges and composite phalange length but not in the distal phalanx.

CONCLUSION

In Afro-Caribbean children, mean radiographic 2D:4D was lower than that of White children and sexual dimorphism of 2D:4D (boys<girls) was confined to the distal phalanx and fingertip soft-tissue. In contrast in White children, there were no sex differences in the distal phalanx but there were in the middle-, proximal and composite phalanges (boys<girls). We discuss whether these differences in 2D:4D are widespread among Blacks and Whites and the implications for the interpretation of radiographic 2D:4D and morphological soft-tissue 2D:4D across macro-ethnic groups.

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.

Digit ratio and hair color relationships with coronary atherosclerotic markers

Objective

We aimed to investigate the association between body phenotype markers and coronary atherosclerosis markers.

Methods

Eighty-nine patients (mean age 57 ± 9 years, 50.5% male) who were assessed for coronary artery disease by 64-slice multidetector computed tomography angiography were enrolled in the study.

Results

A significant positive association was observed between coronary artery calcification and the second to fourth digit ratio ( r = 0.2, p = 0.00); more notably in males compared to females ( p = 0.03 vs. p = 0.08). There was a significant association between coronary artery calcification and pure white hair ( p = 0.00). There was no significant association between pericardial fat volume and second to fourth digit ratio ( p = 0.8). Pericardial fat volume was significantly associated with pure white hair ( p = 0.02). A significant association was observed between coronary plaque and a higher second to fourth digit ratio ( p = 0.01) and this was more notable in males ( p = 0.04). A significant association was observed between pure white hair and coronary plaque ( p = 0.00). After adjustment for conventional cardiac risk factors, the association of coronary artery calcification and coronary plaque with the second to fourth digit ratio did not persist, whereas the association of pericardial fat volume and coronary artery calcification with pure white hair remained significant ( p = 0.01 and p = 0.00, respectively).

Conclusion

These results suggest a possible predictive value of hair color, rather than digit ratio, in assessing increased risk of coronary atherosclerosis and cardiac fat deposition.

The associations between left-hand digit ratio (2D:4D) and puberty characteristics among Chinese girls

BACKGROUND

The aim of this study was to analyse the associations of left-hand digit ratio (2D:4D), digit length and puberty characteristics to show the role of prenatal hormones in development among Chinese girls.

METHOD

A total of 318 Chinese girls aged 8-15 years were recruited using a stratified cluster sampling method. The index finger (2D), ring finger (4D) of the left hand, oestradiol and testosterone were measured, and age at menarche (AAM), breast (high and low) and pubic hair (high and low) development were recorded.

RESULTS

Girls who had experienced menarche had longer left digits (2D and 4D) and higher oestradiol, testosterone than those who had not. The high breast group had longer digits (2D and 4D), and higher oestradiol than the low breast group. With regard to pubic hair development, the high group had high 2D:4D, longer 2D and higher oestradiol, testosterone than the low group. After adjusting for oestradiol and testosterone, 4D length was positively related to occurrence of menarche. In addition, 2D and 2D:4D were significantly correlated with pubic hair development after adjusting for oestradiol, respectively.

CONCLUSION

Prenatal hormone level may be related to the development of puberty characteristics among Chinese girls.

Associations between digit ratio (2D4D), mood, and autonomic stress response in healthy men

The ratio between the length of the second (index) and the fourth (ring) finger (2D4D) is a putative biomarker of prenatal testosterone (T) exposure, with higher exposure leading to a smaller ratio. 2D4D has further been linked to mental and somatic disorders. Healthy male Swiss recruits (N = 245; M_age = 20.30 years) underwent a psychosocial stress test. Mood and salivary alpha-amylase (sAA) were assessed before and after the stress test, while heart rate (HR) and heart rate variability (HRV) were measured continuously. Additionally, 2D4D (right: R2D4D; left: L2D4D) was determined and divided into quartile groups. Correlation analysis showed no associations between R/L2D4D and outcome measures. Comparing calculated quartiles for R2D4D, subjects in the lowest R2D4D quartile expressed trendwise (p < 0.10) lower positive and higher negative affect, significantly elevated sAA activity (p < 0.05), but no HR and HRV differences at baseline as compared to subjects in the upper three quartiles. With regard to acute stress, subjects in the lowest as compared to subjects in the upper three R2D4D quartiles showed a higher increase of negative affect and a stronger cardiac response (p < 0.05), but no alterations in positive affect and sAA activity. Young healthy men in the lowest R2D4D quartile revealed a more negative affect and increased physiological activity at baseline and in response to acute stress. An exposure to high levels of prenatal T might constitute a risk factor potentially increasing vulnerability to stress-related disorders in men.

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.

2D:4D Ratio Differs in Ischemic Stroke: A Single Center Experience

Background

The index to ring finger length (2D:4D) ratio is a proxy biomarker for prenatal exposure of sex hormones. Sex hormones are associated with the pathogenesis of ischemic stroke. The purpose of the study was to demonstrate the association between 2D:4D and ischemic stroke.

Methodology

This study retrospectively reviewed the data of 100 patients with first ever ischemic stroke between September, 2016 and June, 2017. The lengths of index finger and ring finger of both hands were measured using electronic calipers and calculated for 2D:4D ratios. Receive operating characteristic (ROC) mode was used to detect predicting performance of 2D:4D ratios for ischemic stroke.

Results

2D:4D ratios in ischemic stroke patients were higher than controls in both hands (P < 0.05), except right 2D:4D ratio in females. The ROC analyses showed that the area under the curve (AUC) were 0.635 (95%CI: 0.527-0.743) for left 2D:4D ratio, and 0.647 for right (95%CI: 0.539-0.755) (P < 0.05). The AUC of left and right 2D:4D ratio in male were 0.667 (95%CI: 0.514-0.820) and 0.670 (95%CI: 0.519-0.822) (P < 0.05). In female, no significance were found in ROC analysis. And there were no correlation between 2D:4D value and stroke severity (P > 0.05).

Conclusions

The current study indicated that the diagnostic value of 2D:4D ratio was limited in ischemic stroke. Further research is required to explore the role of it in screening ischemic stroke.

Measurement of 2D:4D Ratio and Neck Circumference in Adolescents: Sexual Dimorphism and its Implications in Obesity - A Cross Sectional Study

INTRODUCTION

A bidirectional relationship between testosterone and obesity is explained by the hypogonadal obesity cycle and evidence from reports stating that weight loss leads to increased testosterone levels. There is an alarming rise in the prevalence of obesity among children and adolescents. The objectives of the present study were to measure the 2D:4D ratio of adolescent students and study its association with neck circumference (NC).

MATERIALS AND METHODS

After obtaining ethical clearance, the study was conducted on 168 adolescents pursuing their undergraduate education in a South Indian university. 2D:4D ratio and NC were measured using Digital Vernier Calipers and plastic inch tape, respectively. All the participants were divided into three groups (normal, overweight, and obese) on the basis of their BMI. Mean 2D:4D ratio and NC were compared between the three groups using one-way ANOVA.

RESULTS

Mean right and left hand ratios of the study population were 0.973 ± 0.030 and 0.975 ± 0.069, respectively. Comparison of 2D:4D ratios between the sexes revealed statistical significance (males = 0.966, females = 0.977, and P value = 0.019). There was no significant correlation between 2D:4D ratios and BMI. There was a significant negative correlation between NC and 2D:4D ratios of the individuals with normal BMI. However, no statistically significant correlation between NC and 2D:4D ratios was observed in overweight and obese individuals.

CONCLUSION

2D:4D ratio and NC could be used as simple measures for screening of people at higher risk for heart disease and metabolic syndrome. However, studies on a larger sample might help us reveal the association between NC and 2D:4D ratios.

Digit ratio (2D:4D) and coronary artery disease in north Chinese women

BACKGROUND

Digit ratio (2D:4D) is fixed in utero and affected by fetal sex steroids. It has been proposed as a putative biomarker of certain hormone- related adult life traits and diseases. Several evidence suggest that 2D:4D ratio may correlate with cardiovascular disease risk (e.g., coronary artery disease).

AIMS

To investigate whether there is a possible relationship between digit ratio (especially 2D:4D ratio) and coronary artery disease (CAD), and age at CAD in north Chinese women.

METHODS

Photographs of the two hands of 303 females (controls: 194; patients: 109) were collected. Left hand, right hand and right minus left hand (Dr-l) digit ratio were analyzed and compared.

RESULTS

The mean values of digit ratio in patients with CAD were lower than controls for each hand. Significant differences of 2D:4D (left and right hand: P<0.01), 2D:5D (left hand: P<0.01; right hand: P<0.05) and 3D:4D (left hand: P<0.01) were found between two groups. There were no associations between 2D:4D ratio and age at CAD on both hands.

CONCLUSION

Decreased digit ratio (especially 2D:4D ratio) may suggest a higher prenatal testosterone (lower prenatal oestrogen) exposure in north Chinese women with coronary artery disease.

The Second to Fourth Digit Ratio in Elite and Non-Elite Greco-Roman Wrestlers

A low second-to-fourth digit ratio (2D:4D) has been reported to correlate with high performance and athletic potential of an individual in sport. It has been suggested that 2D:4D is a relatively weak predictor of strength and a stronger predictor of efficiency in aerobic exercise. Comparing extreme groups on a continuum of sports performance requiring high power (physical strength) output would be helpful to resolve this issue. Therefore, the purpose of the present study was to compare the 2D:4D ratio of world-class elite Greco-Roman wrestlers (n = 10) taking part in Olympic fitness camps in 2013 with the 2D:4D ratio of non-elite collegiate wrestlers (n = 20), and age-matched sedentary males (n = 40). The 2D:4D ratios of elite wrestlers were lower compared to non-elite athletes (p < 0.01, right hand d = 1.70, left hand d = 1.67) and the control group (p < 0.0001, right hand d = 3.16, left hand d = 2.00). No significant differences were noted among the groups for right - left 2D:4D. We concluded that 2D:4D may discriminate between non-elite and world-class wrestlers. We also suggest that a low 2D:4D ratio could be linked to performance potential in wrestlers. As such, 2D:4D may provide additional information, which is valuable in determining the potential athleticism of an individual, when it is used in conjunction with other measures.

The effects of prenatal testosterone on wages: Evidence from Russia

Is in utero exposure to testosterone correlated with earnings? The question matters for understanding determinants of wage differences that have attracted so much attention among economists in the past decade. Evidence indicates that markers for early testosterone exposure are correlated with traits like risk-taking and aggressiveness. But it is not at all clear how such findings might map into labor market success. We combine unique data from the Russian Longitudinal Monitoring Survey with measured markers (2D:4D ratios) for testosterone exposure and find that lower digit ratios (higher T) correlate with higher wages for women and for men, when controlling for age, education and occupation. There is also some evidence of a potential non-linear, inverse U-effect of digit ratios on wages but this is sensitive to choice of specification. These findings are consistent with earlier work on prenatal T and success in careers (Coates et al., 2009) but inconsistent with the work of Gielen et al. (2016) who find differing effects for men and women.

FTO Gene Associates and Interacts with Obesity Risk, Physical Activity, Energy Intake, and Time Spent Sitting: Pilot Study in a Nigerian Population

Fat mass and obesity-associated (FTO) gene influences obesity but studies have shown that environmental/lifestyle variables like physical activity (PA), time spent sitting (TSS), and energy intake might mediate the effect. However, this is poorly understood in Nigeria due to scarce studies. We demystified association and interaction between FTO rs9939609, obesity, PA, TSS, and energy intake in Nigeria. FTO gene variant was genotyped by restriction fragment length polymorphism and gene sequencing analysis in 103 people with obesity and 98 controls. Anthropometrics and environmental variables were measured using standard procedures. Significant associations were found between FTO rs9939609 with obesity and environmental/lifestyle variables before and after adjusting for age. Carriers of allele A have significantly higher odds of being overweight/obese using BMI [0.191 (0.102-0.361), p < 0.001] but this was attenuated by PA (p_{[interaction]} = 0.029); odds of being overweight reduced from 0.625 (0.181-2.159) to 0.082 (0.009-0.736) for low and high PA, respectively. Mediation analysis of total indirect effect also confirmed this by showing a simultaneous mediating role of total PA, energy intake, and TSS in the relationship between FTO and BMI (unstandardized-coefficient = 1.68; 95% CI: 1.26-2.22). This study shows a relationship between FTO and obesity phenotype and environmental/lifestyle factors might be an important modulator/mediator in the association.

Neck circumference as a screening measure of overweight/obesity among Indian adults

Neck circumference (NC) is an anthropometric measurement of differentiating body fat distributions and a marker of upper subcutaneous adiposity. The present study highlights the association and importance of NC as a suitable proxy screening measure of overweight/obesity as compared to the conventional anthropometric variables used among Indian adults. The present community based cross-sectional study was undertaken among 1169 Karbi adults (males: 625; females: 544) residing in Karbi Anglong district of Assam, Northeast India, who were selected through a multistage stratified random sampling method. Height, weight, waist circumference (WC), hip circumference (HC) and NC were recorded using standard procedures. The body mass index (BMI) was calculated and prevalence of overweight/obesity was assessed using standard cut-offs. The prevalence of obesity using BMI (≥25.00 kg m-2) was 15.52% and 15.26% among males and females, respectively (p≥0.05).The prevalence of obesity using NC was observed to be significantly higher among males (48.80%) than females (19.12%) (p<0.01). The binary logistic regression analysis showed that NC predicted obesity over the conventional anthropometric variables with reasonable accuracy (p<0.01). The ROC-AUC analysis showed a relatively greater significant association between BMI, WC and HC and NC for obesity (p<0.01). Thus, NC appears to be a potentially simple, easyto- use screening measure for predicting obesity among adults. Further studies are required to validate its use for screening of obesity among other ethnic populations in India.

Low digit ratio (2D:4D) in male suicide victims

Although women attempt suicides equally or more often than men do, men are more likely to die of suicide than women (sex paradox of suicidal behavior). Furthermore, the male traits of aggression and impulsivity predict suicide completion. Here, we studied the second-to-fourth-finger length ratio (2D:4D), a proxy for prenatal androgen exposure, in 46 suicide corpses and 25 non-suicide corpses. We report significantly lower 2D:4D in male suicide corpses than non-suicide corpses (p = .030, partial η ² = .147). There was no significant association between 2D:4D and the suicide method. Our findings indicate increased risk of suicide following higher prenatal androgen exposure in males. The results may improve future efforts to predict and prevent suicides.

Neck Circumference Is Not Associated with Dysphagia but with Undernutrition in Elderly Individuals Requiring Long-term Care

OBJECTIVES

The purpose was to assess the association between neck circumference, dysphagia, and undernutrition in elderly individuals requiring long-term care.

DESIGN

Cross-sectional study.

SETTING

Geriatric health services facilities, acute hospitals, and the community.

PARTICIPANTS

Elderly individuals ≥65 years of age with dysphagia or possible dysphagia (N=385).

MEASUREMENTS

Neck circumference, the Dysphagia Severity Scale (DSS) and the Mini Nutritional Assessment Short Form (MNA-SF).

RESULTS

Participants included 130 males and 255 females with a mean age (± standard deviation) of 83 ± 8.0 years. Sixty-six were in acute hospitals, 195 were in geriatric health services facilities, and 124 were community-dwelling. The mean neck circumference in males and females was 37.1 ± 3.0 cm and 33.3 ± 3.3 cm, respectively. Based on the DSS, 81 participants were within normal limits, 137 had dysphagia without aspiration, and 167 had dysphagia with aspiration. The MNA-SF revealed that 173 were malnourished, 172 were at risk of malnutrition, and 40 had a normal nutritional status. Neck circumference was not significantly correlated with the DSS (r=-0.080) but was significantly correlated with the MNA-SF (r=0.183) in the Spearman rank correlation analysis. In the logistic regression, neck circumference was not independently associated with the DSS after adjusting for the MNA-SF, the Barthel Index, age, sex, setting, and cerebrovascular disorders. However, the multiple regression analysis showed that neck circumference had an independent effect on the MNA-SF after adjusting for the Barthel Index, age, sex, setting and cerebrovascular disorders.

CONCLUSIONS

Neck circumference is not associated with dysphagia but with undernutrition in elderly individuals requiring long-term care.

Hadza hunter-gatherer men do not have more masculine digit ratios (2D:4D)

OBJECTIVES

The ratio between the length of the second and the length of the fourth digit (2D:4D) is sexually dimorphic such that males of many species possess a lower ratio than females, particularly in the right hand. Still, men and women often exhibit overlapping 2D:4D ranges and the ratio is highly variable between populations. In order to further explore populational variability, we chose to analyze 2D:4D in the Hadza, a population of hunter-gatherers living in Tanzania.

MATERIALS AND METHODS

Data were collected separately by two researchers over the course of three years (1998, 2001, 2006) from 152 adult participants (male: n = 76, female: n = 76). Independent samples t-tests were used to explore sex differences, paired samples t-tests were used to explore directional effects within each sex, and linear regression and one-way ANOVA were used to test possible age effects.

RESULTS

In none of the years, or pooled (n = 152), did we find evidence that adult men have a lower 2D:4D than adult women. If anything, the data suggest that women in this population have a significantly lower right hand 2D:4D than men (P < 0.001, d = 0.57). In contrast, left hand 2D:4D did not exhibit a sex difference (P = 0.862, d = 0.03).

DISCUSSION

These findings challenge the current view that lower 2D:4D in men is a uniform characteristic of our species. Cross-populational variance in 2D:4D may be related to known patterns of hormonal variation resulting from both genetic and environmental mechanisms, though this relationship merits further investigation.

Second to fourth digit ratio (2D:4D) and coronary heart disease

INTRODUCTION

Sex steroid exposure during human development may influence disease susceptibility. Second to fourth digit ratio (2D:4D) is thought to be a putative biomarker for prenatal hormone level during foetal life. Recently there has been a great deal of interest in 2D:4D and risk of disease in adulthood.

METHODS

We explored the relationship between 2D:4D ratio and coronary heart disease. Photocopies of the two hands of 310 males (controls: 155; patients: 155) were collected at Yin chuan city, in the Ningxia province of China. Left hand, right hand, mean hand and right minus left 2D:4D (Dr-l) were analysed.

RESULTS

The mean values of 2D:4D ratio in patients were higher than those of CSIN controls. The patients showed significantly higher 2D:4D (left hand: P < 0.01; right hand, mean hand: P < 0.05) than controls. In patients, 2D:4D (especially left hand 2D:4D) were inversely associated with age at diagnosis (left hand: P < 0.001; right hand, mean hand: P < 0.05). No association between Dr-l and age or age at presentation of disease was observed in the groups.

CONCLUSION

2D:4D may correlate particularly with risk of coronary heart disease in Chinese men.

Finger length pattern as a biomarker for osteoarthritis and chronic joint pain: a population-based study and meta-analysis after systematic review

OBJECTIVE

Type 3 finger length pattern (longer fourth digit than second digit) is influenced by prenatal androgens and has been studied previously as a biomarker for sexually dimorphic traits. Because osteoarthritis (OA) and chronic pain are known to be sexually dimorphic traits, we evaluated the association between finger length pattern and OA and chronic joint pain.

METHODS

This study was part of the Rotterdam Study, a prospective population-based cohort study. We examined 4,784 participants. Associations between type 3 finger length and radiologic knee, hip, and hand OA and chronic joint pain were analyzed using a logistic regression model. Our results for OA were combined with previously published data in a meta-analysis.

RESULTS

Participants with type 3 finger length pattern had an odds ratio of 1.64 for hand OA (P = 1.06 × 10(-7)). No associations with radiologic knee or hip OA were observed in the Rotterdam Study. The meta-analysis of previously published data and our novel data showed a significant association between type 3 finger length pattern and clinical symptomatic knee OA, but no association was found with radiologic knee OA. In addition, within the Rotterdam Study, we observed an odds ratio of 1.41 for individuals having joint pain at multiple sites (P = 1.4 × 10(-3)).

CONCLUSION

Type 3 finger length pattern, as an indicator of prenatal androgen exposure, was associated with having symptomatic knee OA, chronic pain, and hand OA. Therefore, it may be applicable as an easy measurable biomarker to identify susceptible subjects for these traits.

Neck circumference and lowest oxygen saturation are independently associated with high coexistence of hypertension in obstructive sleep apnea

PURPOSE

Obstructive sleep apnea (OSA) is considered an independent risk factor for hypertension. However, it is still not clear which clinical factors are related with the presence of hypertension in OSA patients. We aimed to find different physical features and compare the sleep study results which are associated with the occurrence of hypertension in OSA patients.

MATERIALS AND METHODS

Medical records were retrospectively reviewed for patients diagnosed with OSA at Severance Cardiovascular Hospital between 2010 and 2013. Males with moderate to severe OSA patients were enrolled in this study. Clinical and polysomnographic features were evaluated to assess clinical variables that are significantly associated with hypertension by statistical analysis.

RESULTS

Among men with moderate to severe OSA, age was negatively correlated with hypertension (odds ratio=0.956), while neck circumference was positively correlated with the presence of hypertension (odds ratio=1.363). Among the polysomnographic results, the lowest O₂ saturation during sleep was significantly associated with the presence of hypertension (odds ratio=0.900).

CONCLUSION

Age and neck circumference should be considered as clinically significant features, and the lowest blood O₂ saturation during sleep should be emphasized in predicting the coexistence or development of hypertension in OSA patients.

The correlation of right 2D:4D finger length ratio to the low-grade inflammation marker IL-6 in children. The Healthy Growth Study

BACKGROUND

Second to fourth digit ratio (2D:4D) is associated with cardiometabolic risk in adults.

AIM

To examine the association of right 2D:4D with cardiovascular disease risk factors in children.

STUDY DESIGN

Cross-sectional study.

SUBJECTS

A sample of 301 children (53.5% girls) aged 9-13 in Greece and their parents. Children who were sick during the previous week of examination (n=44) were excluded from the analyses.

OUTCOME MEASURES

Socio-demographic (gestational age, birth weight, age, gender, maternal education level), anthropometric (body weight and height, finger length), clinical (pubertal stage, sickness during the previous week of the examination), blood [serum high sensitivity C-reactive protein (CRP), serum high sensitivity interleukin-6 (IL-6), serum leptin], lifestyle (dietary intake, maternal smoking during pregnancy) and physical fitness (handgrip strength) data were collected. CRP, IL-6 and leptin were measured with ELISA, using standard equipment and procedures, in accordance with manufacturers' instructions.

RESULTS

Full data were available for 257 children (52.1% girls). The rank values of right 2D:4D and IL-6 were included in the analyses. Right 2D:4D was correlated only with IL-6 at a bivariate level (r=0.216, p=0.012) in girls. At a linear multivariate level, this association remained significant, even after adjusting for several potential confounders such as age, Tanner stage, maternal education level, body mass index, maternal smoking during pregnancy, duration of pregnancy, protein-, carbohydrate-, fat-intake and physical fitness (β±SE=0.220±0.066, p=0.001).

CONCLUSIONS

Right 2D:4D was found to be associated with IL-6 in girls. Right 2D:4D may be a valuable, simple screening tool of low-grade inflammation in children.

The association between metacarpal ratio, radiographic hand and knee osteoarthritis and its progression after meniscectomy

OBJECTIVE

To examine whether the ratio of the second and fourth metacarpal bone length (MC2:MC4) in subjects with prior meniscectomy of the knee is associated with radiographic hand and knee osteoarthritis (OA) and its progression.

DESIGN

We assessed 219 subjects (175 men and 44 women) twice with a follow-up time ranging from 4 to 10 years. Participants had all undergone prior meniscectomy. The subjects were of mean (SD) 53 (11) years of age at the first radiographic examination. One observer measured the metacarpal lengths of both hands. We used the average MC2:MC4 from left and right hand divided into tertiles as the exposure variable, using the highest tertile, i.e., "female" pattern as reference category. Radiographic OA of both hands and knees and its progression were evaluated on subject level as our outcomes. We used logistic regression to evaluate the possible association of MC2:MC4 with hand and knee OA and its progression with adjustment for age, sex, body mass index, and follow-up time.

RESULTS

We found no statistically significant association between the lower MC2:MC4 tertile "male" pattern and prevalent hand OA (odds ratio [OR] 0.70; 95% confidence interval [CI] 0.24-1.99) and prevalent knee OA (OR 1.08; 95% CI 0.56-2.07). Neither did we find any corresponding significant association for the progression of hand OA (OR 0.89; 95% CI 0.34-2.32), nor knee OA (OR 0.69; 95% CI 0.33-1.46).

CONCLUSIONS

We did not detect any association between MC2:MC4 and radiographic hand and knee OA and its progression in subjects with prior meniscectomy.

Digit ratio (2D:4D) and competition level in world-class female gymnasts

In this study the relationship between the digit ratio (2D:4D) and artistic gymnastics performance and competition level was investigated in a sample of Caucasian world-class female gymnasts (n = 145). The sample was divided into three competition events (compulsories, free work, final score). Within each event three performance groups (lowest, middle, and highest) were based on the competition scores gathered at the World Championships at Rotterdam, the Netherlands, in 1987. Lengths of the digits were measured on X-rays of the left hand. Several anthropometric dimensions were measured and from those measurements an androgyny index (Bayer & Bayley) and somatotype components (endomorphy, mesomorphy, ectomorphy) were calculated. Although significant differences in some anthropometric characteristics between the performance level groups within each competition event were observed, no significant differences in the 2D:4D ratios were found between the performance level groups, varying from 0.918 ± 0.020 to 0.924 ± 0.020. Also, no significant correlations were observed between the 2D:4D ratio and anthropometric, androgyny, and somatotype characteristics, r varying from r = -0.11 to r = +0.12. It can be concluded that in this sample the 2D:4D digit ratio, unlike other anthropometric characteristics, is not a discriminating factor for the performance in artistic gymnastics performance on a world-class level.

The ratio of second to fourth digit length (2D:4D) and coronary artery disease in a Han Chinese population

BACKGROUND

The association between index finger to ring finger length ratio (2D:4D) and cardiac disorders has been reported, however it has not been discussed in terms of coronary artery disease (CAD). We investigated whether 2D:4D could be used as a marker for predisposition to CAD as assessed by coronary angiography in Chinese men and women.

METHODS

This study included 1764 persons divided into 4 groups, 441 cases with CAD and 441 persons without CAD as control in each sex of the same age. Finger lengths were measured twice for both hands using electronic calipers. Student t test was used to detect the difference of 2D:4D among groups. The receiver operator characteristic curves (ROCs) were used to detect the diagnostic effect of 2D:4D for CAD.

RESULTS

There were no significant differences in age among the four groups. A significant difference of 2D:4D ratios between right and left hand were observed only in men in both control and CAD groups. On the right hand in the control group and on both hands in the CAD group, the 2D:4D ratios were higher in women than in men (all, P < 0.001). In men with CAD, mean 2D:4D was higher than mean 2D:4D in control men (right hand 0.962±0.042:0.927±0.038; left hand 0.950±0.044:0.934±0.048; both hands, P < 0.001), but this was not observed in women. No relationship was found between 2D:4D and age (all, P >0.05). The area under the curve of right hand 2D:4D in male was 0.72 (95% CI 0.683-0.753, p<0.001), while it was 0.602 (95% CI 0.565-0.639, p<0.001) in left hand.

CONCLUSIONS

The present study showed an association between high 2D:4D ratio and CAD in both hands in men. There were no significant differences in mean 2D:4D between women with CAD and controls.

Genetic association suggests that SMOC1 mediates between prenatal sex hormones and digit ratio

Men and women differ statistically in the relative lengths of their index and ring fingers; and the ratio of these lengths has been used as a biomarker for prenatal testosterone. The ratio has been correlated with a wide range of traits and conditions including prostate cancer, obesity, autism, ADHD, and sexual orientation. In a genome-wide association study of 979 healthy adults, we find that digit ratio is strongly associated with variation upstream of SMOC1 (rs4902759: P = 1.41 × 10(-8)) and a meta-analysis of this and an independent study shows a probability of P = 1.5 × 10(-11). The protein encoded by SMOC1 has recently been shown to play a critical role in limb development; its expression in prostate tissue is dependent on sex hormones, and it has been implicated in the sexually dimorphic development of the gonads. We put forward the hypothesis that SMOC1 provides a link between prenatal hormone exposure and digit ratio.

The left hand second to fourth digit ratio (2D:4D) does not discriminate world-class female gymnasts from age matched sedentary girls

Introduction

The second to fourth-digit-ratio (2D:4D), a putative marker of prenatal androgen action and a sexually dimorphic trait, has been suggested to be related with sports performance, although results are not univocal. If this relation exists, it is most likely to be detected by comparing extreme groups on the continuum of sports performance.

Methods

In this study the 2D:4D ratio of world-class elite female artistic gymnasts (n = 129), competing at the 1987 Rotterdam World-Championships was compared to the 2D:4D ratio of sedentary age-matched sedentary girls (n = 129), alongside with other anthropometric characteristics including other sexually dimorphic traits such as an androgyny index (Bayer & Bayley) and Heath-Carter somatotype components (endomorphy, mesomorphy, ectomorphy) using AN(C)OVA. 2D:4D was measured on X-rays of the left hand.

Results

Left hand 2D:4D digit ratio in world class elite female gymnasts (0.921±0.020) did not differ significantly from 2D:4D in age-matched sedentary girls (0.924±0.018), either with or without inclusion of potentially confounding covariates such as skeletal age, height, weight, somatotype components or androgyny index. Height (161.9±6.4 cm vs 155.4±6.6 cm p<0.01), weight (53.9±7.6 kg vs 46.2 6.3 kg p<0.01), BMI (20.51±2.41 kg/m² vs 19.05±1.56 kg/m²), skeletal age (15.2±1.1 y vs 14.5±1.2 y p>0.01), somatotype components (4.0/3.0/2.9 vs 1.7/3.7/3.2 for endomorphy (p<0.01), mesomorphy (p<0.01) and ectomorphy (p<0.05) respectively) all differed significantly between sedentary girls and elite gymnasts. As expressed by the androgyny index, gymnasts have, on average, broader shoulders relative to their hips, compared to the reference sample. Correlations between the 2D:4D ratio and chronological age, skeletal age, and the anthropometric characteristics are low and not significant.

Conclusion

Although other anthropometric characteristics of sexual dimorphism were significantly different between the two samples, the present study cannot discriminate sedentary girls from world-class female gymnasts by means of the left hand 2D:4D ratio.

The relationship between second-to-fourth digit ratio and female gender identity

INTRODUCTION

Gender identity and the second-to-fourth finger length ratio (2D : 4D) are discriminative between the sexes. However, the relationship between 2D : 4D and gender identity disorder (GID) is still controversial.

AIM

The aim of this study is to investigate the relationship between 2D : 4D and score on the Gender Identity Scale (GIS) in female-to-male (FtM) GID subjects.

METHODS

Thirty-seven GID-FtM with testosterone replacement therapy from our clinic were included in this study. As controls, 20 male and 20 female volunteers participated from our institution (medical doctors and nurses). We photocopied left and right hands of the participants and measured the second and fourth finger lengths. Gender identity was measured with the GIS.

MAIN OUTCOME MEASURES

2D : 4D digit ratio and GIS in male, female, and GID-FtM subjects.

RESULTS

The 2D : 4D (mean ± standard deviation) in male, female, and GID-FtM were 0.945 ± 0.029, 0.999 ± 0.035, and 0.955 ± 0.029 in right hand and 0.941 ± 0.024, 0.979 ± 0.040, and 0.954 ± 0.036 in left hand, respectively. The 2D : 4D was significantly lower in male controls in both hands and GID-FtM in the right hand than in female controls (P < 0.05, analysis of variance). Multiple linear regression analysis revealed that "consistent gender identity" score in the higher domain in GIS and "persistent gender identity" score in the lower domain are statistically significant variables correlating with 2D : 4D in the right hands among biological females.

CONCLUSIONS

The finger length ratio 2D : 4D in GID-FtM was significantly lower than in female controls in the right hand in this study. 2D : 4D showed a positive correlation with GIS score. Because 2D : 4D influences are assumed to be established in early life and to reflect testosterone exposure, our results suggest a relationship between GID-FtM and perinatal testosterone.

Meta-analysis of digit ratio 2D:4D shows greater sex difference in the right hand

OBJECTIVES

Our aims are, first, to describe the sex difference in the length ratio of the second and fourth digits (2D:4D), which likely reflects prenatal testosterone levels in humans. Second, to infer the loss of reliability observed in 2D:4D based on self-measured finger lengths.

METHODS

We used random-effects meta-analysis of 2D:4D based on expert-measured finger lengths (116 samples with 13,260 females and 11,789 males).

RESULTS

We find a moderate sex difference (with lower 2D:4D for males), which shows substantial heterogeneity (which is unrelated to age). The sex difference is moderated by the type of finger length measurement and by hand. Measurement involving the distortion of soft tissue leads to a significantly larger sex difference than finger length measurement avoiding this. The sex difference in 2D:4D is larger in the right hand than in the left. The reliability of self-measured 2D:4D in the BBC internet study, by far the largest study on 2D:4D, is estimated to be 46% of that of expert-measured 2D:4D.

CONCLUSIONS

Right-hand 2D:4D might be a better indicator of prenatal androgenisation than left-hand 2D:4D. The view that 2D:4D has allometric properties (Kratochvil L, Flegr J. 2009. Differences in 2nd to 4th digit length ratio in humans reflect shifts along the common allometric line. Biol Lett 5:643-646.) is not supported. Bone lengths contribute to the sex difference in 2D:4D. In addition, there might be a sex difference in fingers' soft tissue, which should be investigated. Because of measurement unreliability, correlations between 2D:4D and variables of interest are about one-third smaller in the BBC internet study than in studies in which 2D:4D is based on expert-measured finger lengths.

Index to ring digit ratio in Saudi Arabia at Almadinah Almonawarah province: a direct and indirect measurement study

The digit ratio, or the relative lengths, of the 2nd and 4th digits (2D :4D) shows a sex difference, with males tending to have lower values in comparison with females. This sex differences arises early in the fetus and may result from the effects of prenatal testosterone and estrogen on the relative growth rate of the 2nd and 4th digits. This study aimed to estimate finger lengths and the 2D:4D ratios for the first time in Saudi Arabian subjects using direct and indirect measurements, and to evaluate the correlations between both indirect and direct 2D:4D with adult testosterone and various sexually dimorphic physical traits. The results revealed the following: (i) mean 2D:4D in Saudi Arabian samples varied from 0.96 to 0.99; (ii) mean 2D:4D was lower for indirect compared to direct 2D:4D; (iii) sex differences in indirect 2D:4D were higher than in direct 2D:4D measurements; (iv) there were no significant correlations between indirect or direct 2D:4D and testosterone level; (v) there were four significant correlations between direct 2D:4D and body size traits but no significant correlations between indirect 2D:4D and body size.

Site specific osteoarthritis and the index to ring finger length ratio

OBJECTIVE

To quantify the relationship between the index to ring finger length ratio second digit:fourth digit(2D:4D) and radiographic osteoarthritis (OA) of the knee.

METHODS

Data from the Clearwater Osteoarthritis Study (COS) were analyzed. We selected a random sample of 236 subjects with knee OA (Kellgren-Lawrence scores >or=2) and compared their finger length ratio pattern with a random sample of 242 controls. Finger length measurements were recorded from digitized hand radiographs. Subjects were classified into three groups: type 1 (index finger longer than ring finger), type 2 (fingers of equal length) and type 3 (index finger shorter than ring finger). Using a case-control design, we calculated odds ratios (OR).

RESULTS

The type 3 finger pattern was significantly associated with knee OA (OR 2.59, 95% confidence interval (CI) 1.54-4.37). Women demonstrated a stronger association of visual type 3 finger pattern and knee OA (OR 4.40, 95% CI 2.62-7.38) compared to men (OR 2.59, 95% CI 1.34-5.00).

CONCLUSIONS

The type 3 finger length pattern is associated, to a statistically significant degree, with OA of the knee. The type 3 finger length pattern (ring finger longer than index finger) appears to be an indicator of OA predisposition. Consideration of this pattern in clinical assessments may be an added aid as clinicians screen patients for OA risk.

Scientometric analysis and bibliography of digit ratio (2D:4D) research, 1998-2008

A scientometric analysis of modern research on the second-to-fourth digit ratio (2D:4D), a widely studied putative marker for prenatal androgen action, is presented. In early 2009, this literature totalled more than 300 publications and, since its initiation in 1998, has grown at a rate slightly faster than linear. Key findings included evidence of publication bias and citation bias, incomplete coverage and outdatedness of existing reviews, and a dearth of meta-analyses in this field. 2D:4D research clusters noticeably in terms of researchers, institutions, countries, and journals involved. Although 2D:4D is an anthropometric trait, most of the research has been conducted at psychology departments, not anthropology departments. However, 2D:4D research has not been predominantly published in core and specialized journals of psychology, but rather in more broadly scoped journals of the behavioral sciences, biomedical social sciences, and neurosciences. Total citation numbers of 2D:4D papers for the most part were not larger than their citation counts within 2D:4D research, indicating that until now, only a few 2D:4D studies have attained broader interest outside this specific field. Comparative citation analyses show that 2D:4D research presently is commensurate in size and importance to evolutionary psychological jealousy research, but has grown faster than the latter field. In contrast, it is much smaller and has spread more slowly than research about the Implicit Association Test Fifteen conjectures about anticipated trends in 2D:4D research are outlined, appendixed by a first-time bibliography of the entirety of the published 2D:4D literature.