http://www.dundee.ac.uk/iea/Davey_Smith.htm
Sex and death: are they related? Findings from the Caerphilly cohort study
George Davey Smith, professor of clinical epidemiology, Stephen Frankel, professor of epidemiology and public health medicine, John Yarnell, senior lecturer
Department of Social Medicine, University of Bristol, Bristol, BS8 2PR, b Department of Epidemiology and Public Health, Queen's University of Belfast, Belfast BT12 6BJ

Objective: To examine the relation between frequency of orgasm and mortality.
Study design: Cohort study with a 10 year follow up.
Setting: The town of Caerphilly, South Wales, and five adjacent villages.
Subjects: 918 men aged 45-59 at time of recruitment between 1979 and 1983.
Main outcome measures: All deaths and deaths from coronary heart disease.
Result: Mortality risk was 50% lower in the group with high orgasmic frequency than in the group with low orgasmic frequency, with evidence of a dose-response relation across the groups. Age adjusted odds ratio for all cause mortality was 2.0 for the group with low frequency of orgasm (95% confidence interval 1.1 to 3.5, test for trend P=0.02). With adjustment for risk factors this became 1.9 (1.0 to 3.4, test for trend P=0.04). Death from coronary heart disease and from other causes showed similar associations with frequency of orgasm, although the gradient was most marked for deaths from coronary heart disease. Analysed in terms of actual frequency of orgasm, the odds ratio for total mortality associated with an increase in 100 orgasms per year was 0.64 (0.44 to 0.95).
Conclusion: Sexual activity seems to have a protective effect on men's health.

The ratio of 2nd to 4th digit length and male homosexuality.
Robinson SJ, Manning JT.
Population and Evolutionary Biology Research Group, School of Biological Sciences, University of Liverpool, L69 3BX, Liverpool, UK

Sexual orientation may be influenced by prenatal levels of testosterone and oestrogen.
There is evidence that the ratio of the length of 2nd and 4th digits (2D:4D) is negatively related to prenatal testosterone and positively to oestrogen.
We report that (a) 2D:4D was lower in a sample of 88 homosexual men than in 88 sex- and age-matched controls recruited without regard to sexual orientation, (b) within the homosexual sample, there was a significant positive relationship between mean 2D:4D ratio and exclusive homosexuality, (c) overall, there was a decrease in 2D:4D from controls to homosexual men to bisexual men and (d) fraternal birth order, a positive predictor of male homosexuality, was not associated with 2D:4D in a sample of 240 Caucasian men recruited without regard to sexual orientation and 45 homosexual men.
Further work is needed to confirm the relationships between 2D:4D and sexual orientation. However, these and other recent data tend to support an association between male homosexuality and high fetal testosterone. Very high testosterone levels may be associated with a sexual preference for both men and women.

The ratio of 2nd to 4th digit length: a predictor of sperm numbers and concentrations of testosterone, luteinizing hormone and oestrogen.
Manning JT, Scutt D, Wilson J, Lewis-Jones DI.
Population Biology Research Group, School of Biological Sciences, The University of Liverpool, UK.

The differentiation of the urinogenital system and the appendicular skeleton in vertebrates is under the control of Hox genes. The common control of digit and gonad differentiation raises the possibility that patterns of digit formation may relate to spermatogenesis and hormonal concentrations.
This work was concerned with the ratio between the length of the 2nd and 4th digit (2D:4D) in humans. We showed that (i) 2D:4D in right and left hands has a sexually dimorphic pattern; in males mean 2D:4D = 0.98, i.e. the 4th digit tended to be longer than the 2nd and in females mean 2D:4D = 1.00, i.e. the 2nd and 4th digits tended to be of equal length.
The dimorphism is present from at least age 2 years and 2D:4D is probably established in utero; (ii) high 2D:4D ratio in right hands was associated with germ cell failure in men (P = 0.04); (iii) sperm number was negatively related to 2D:4D in the right hand (P = 0.004); (iv) in men testosterone concentrations were negatively related to right hand 2D:4D and in women and men LH (right hand), oestrogen (right and left hands) and prolactin (right hand) concentrations were positively correlated with 2D:4D ratio and (v) 2D:4D ratio in right hands remained positively related to luteinizing hormone and oestrogen after controlling for sex, age, height and weight