Tuesday, June 30, 2009

Daily sex improves sperm quality

Daily sex helps to reduce sperm DNA damage and improve fertility

Amsterdam, The Netherlands: Daily sex (or ejaculating daily) for seven days improves men's sperm quality by reducing the amount of DNA damage, according to an Australian study presented today (Tuesday) to the 25th annual meeting of the European Society of Human Reproduction and Embryology in Amsterdam.

Until now there has been no evidence-based consensus amongst fertility specialists as to whether or not men should refrain from sex for a few days before attempting to conceive with their partner, either spontaneously or via assisted reproduction.

Dr David Greening, an obstetrician and gynaecologist with sub specialist training in reproductive endocrinology and infertility at Sydney IVF, Wollongong, Australia, said: "All that we knew was that intercourse on the day of ovulation offered the highest chance of pregnancy, but we did not know what was the best advice for the period leading up to ovulation or egg retrieval for IVF.

"I thought that frequent ejaculation might be a physiological mechanism to improve sperm DNA damage, while maintaining semen levels within the normal, fertile range."

To investigate this hypothesis, Dr Greening studied 118 men who had higher than normal sperm DNA damage as indicated by a DNA Fragmentation Index (DFI). Men who had a more than 15% of their sperm (DFI >15%) damaged were eligible for the trial. At Sydney IVF, sperm DNA damage is defined as less than 15% DFI for excellent quality sperm, 15-24% DFI for good, 25-29% DFI for fair and more than 29% DFI for poor quality; but other laboratories can have slightly different ranges.

The men were instructed to ejaculate daily for seven days, and no other treatment or lifestyle changes were suggested. Before they started, levels of DNA damage ranged between 15% and 98% DFI, with an average 34% DFI when measured after three days' abstinence. When the men's sperm was re-assessed on the seventh day, Dr Greening found that 96 men (81%) had an average 12% decrease in their sperm DNA damage, while 22 men (19%) and an average increase in damage of nearly 10%. The average for the whole group dropped to 26% DFI.

Dr Greening said: "Although the mean average was 26% which is in the 'fair' range for sperm quality, this included 18% of men whose sperm DNA damage increased as well as those whose DNA damage decreased. Amongst the men whose damage decreased, their average dropped by 12% to just under 23% DFI, which puts them in the 'good' range. Also, more men moved into the 'good' range and out of the 'poor' or 'fair' range. These changes were substantial and statistically highly significant.

"In addition, we found that although frequent ejaculation decreased semen volume and sperm concentrations, it did not compromise sperm motility and, in fact, this rose slightly but significantly.

"Further research is required to see whether the improvement in these men's sperm quality translates into better pregnancy rates, but other, previous studies have shown the relationship between sperm DNA damage and pregnancy rates.

"The optimal number of days of ejaculation might be more or less than seven days, but a week appears manageable and favourable. It seems safe to conclude that couples with relatively normal semen parameters should have sex daily for up to a week before the ovulation date. In the context of assisted reproduction, this simple treatment may assist in improving sperm quality and ultimately achieving a pregnancy. In addition, these results may mean that men play a greater role in infertility than previously suspected, and that ejaculatory frequency is important for improving sperm quality, especially as men age and during assisted reproduction cycles."

Dr Greening said he thought the reason why sperm quality improved with frequent ejaculation was because the sperm had a shorter exposure in the testicular ducts and epididymis to reactive oxygen species – very small molecules, high levels of which can damage cells. "The remainder of the men who had an increase in DFI might have a different explanation for their sperm DNA damage," he concluded.

Monday, June 29, 2009

Vibrator use is common, linked to sexual health

Two Indiana University studies conducted among nationally representative samples of adult American men and women show that vibrator use during sexual interactions is common, with use being reported by approximately 53 percent of women and 45 percent of men ages 18 to 60. Not only is vibrator use common, but the two studies also show that vibrator use is associated with more positive sexual function and being more proactive in caring for one's sexual health.

The studies, led by researchers at the Center for Sexual Health Promotion in IU's School of Health, Physical Education and Recreation, are the first to publish data about vibrator use from nationally representative samples of the U.S. population. This lack of data has existed despite a longstanding practice by many physicians and therapists to recommend vibrator use to help treat sexual dysfunctions or to improve sexual enjoyment.

One study surveyed women. The other surveyed men. Both were published this week by the "Journal of Sexual Medicine," a leading peer-reviewed journal in the area of urology and sexual health.

"The study about women's vibrator use affirms what many doctors and therapists have known for decades -- that vibrator use is common, it's linked to positive sexual function such as desire and ease of orgasm, and it's rarely associated with any side effects," said Debby Herbenick, associate director of the Center for Sexual Health Promotion.

Michael Reece, director of the Center for Sexual Health Promotion, said the studies are important for the contributions they make to an understanding of the sexual behaviors and sexual health of adults in today's society.

"The study about male vibrator use is additionally important because it shows that vibrator use is also common among men, something that has not been documented before," Reece said. "Also, both studies help us to further understand the way in which American consumers are turning to the marketplace for products that promote their sexual health, and that has important economic implications."

The studies are the first to document insights into how and why people use vibrators, examine side effects and to explore associations with sexual health behaviors, sexual enjoyment and quality of life measures.

The studies were funded by Church & Dwight Co. Inc., maker of Trojan® brand sexual health products. Here are some of the findings from the studies, which involve survey responses from 2,056 women and 1,047 men ages 18-60.

For women:

More than half of the women (52.5 percent) had used a vibrator with nearly one in four having done so in the past month.

Vibrator users were significantly more likely to have had a gynecological exam during the past year and to have performed genital self-examination during the previous month.
Vibrator use was positively related to several aspects of sexual function (desire, arousal, lubrication, orgasm, pain and overall function) with recent vibrator users scoring themselves higher on most sexual function domains, suggesting more positive sexual function.

Most women (71.5 percent) reported having never experienced any side effects associated with vibrator use. Those side effects that were reported were typically rare and of a short duration.

For men:

The prevalence of men who had incorporated a vibrator into sexual activities during their lives was 44.8 percent, with no statistical differences between the rates of vibrator use between men who identified as heterosexual and those who identified as gay or bisexual.

Heterosexual men most commonly reported having used vibrators during foreplay or intercourse with a female partner, with 91 percent of those who had used a vibrator reporting that they had done so during such activities with women.

Of men who have used vibrators, 10 percent had done so in the past month, 14.2 percent in the past year and 20.5 percent more than one year ago.

Men who reported having used vibrators, particularly those with more recent use, were more likely to report participation in sexual health promoting behaviors, such as testicular self-exam.

Men who had used vibrators recently also scored themselves higher on four of the five domains of sexual function, as measured by the International Index of Erectile Function (erectile function, intercourse satisfaction, orgasmic function and sexual desire).

The study specifically sought to establish nationally representative rates of vibrator use among men and women in the United States. Vibrators are electrical devices that produce pulses of variable amplitude and frequency to enhance sexual arousal in men and women by stimulating the genitals. Marketed widely to women through the Internet, women's magazines, boutiques and in-home sex toy parties, they also are available in drug stores and other mainstream retailers.

Hot or not? Men agree. Women don't.

Rating attractiveness: Study finds consensus among men, not women

There is much more consensus among men about whom they find attractive than there is among women, according to a new study by Wake Forest University psychologist Dustin Wood.

The study, co-authored by Claudia Brumbaugh of Queens College, appears in the June issue of the Journal of Personality and Social Psychology.

"Men agree a lot more about who they find attractive and unattractive than women agree about who they find attractive and unattractive," says Wood, assistant professor of psychology. "This study shows we can quantify the extent to which men agree about which women are attractive and vice versa."

More than 4,000 participants in the study rated photographs of men and women (ages 18-25) for attractiveness on a 10-point scale ranging from "not at all" to "very." In exchange for their participation, raters were told what characteristics they found attractive compared with the average person. The raters ranged in age from 18 to more than 70.

Before the participants judged the photographs for attractiveness, the members of the research team rated the images for how seductive, confident, thin, sensitive, stylish, curvaceous (women), muscular (men), traditional, masculine/feminine, classy, well-groomed, or upbeat the people looked.

Breaking out these factors helped the researchers figure out what common characteristics appealed most to women and men.

Men's judgments of women's attractiveness were based primarily around physical features and they rated highly those who looked thin and seductive. Most of the men in the study also rated photographs of women who looked confident as more attractive.

As a group, the women rating men showed some preference for thin, muscular subjects, but disagreed on how attractive many men in the study were. Some women gave high attractiveness ratings to the men other women said were not attractive at all.

"As far as we know, this is the first study to investigate whether there are differences in the level of consensus male and female raters have in their attractiveness judgments," Wood says. "These differences have implications for the different experiences and strategies that could be expected for men and women in the dating marketplace."

For example, women may encounter less competition from other women for the men they find attractive, he says. Men may need to invest more time and energy in attracting and then guarding their mates from other potential suitors, given that the mates they judge attractive are likely to be found attractive by many other men.

Wood says the study results have implications for eating disorders and how expectations regarding attractiveness affect behavior.

"The study helps explain why women experience stronger norms than men to obtain or maintain certain physical characteristics," he says. "Women who are trying to impress men are likely to be found much more attractive if they meet certain physical standards, and much less if they don't. Although men are rated as more attractive by women when they meet these physical appearance standards too, their overall judged attractiveness isn't as tightly linked to their physical features."

The age of the participants also played a role in attractiveness ratings. Older participants were more likely to find people attractive if they were smiling.

Wednesday, June 10, 2009

Young men scarce, are more likely to play the field

In places where young women outnumber young men, research shows the hemlines rise but the marriage rates don't because the young men feel less pressure to settle down as more women compete for their affections.

But when those men reach their 30s, the reverse is true and proportionately more older men are married in areas where women outnumber men.

Daniel Kruger, a University of Michigan researcher who studies evolution and how it relates to contemporary behavior, looked at the 50 largest metropolitan areas in the United States to test his hypothesis on how the balance between women and men affects marital patterns. Results showed that men aged 20-24 are more likely to cruise than to commit if they live in an area with more women than men.

One would think that rationally, fewer young men than women would naturally lead to proportionately more young men getting married, but that's not the case.

"Marriage patterns aren't rational because men and women have somewhat different reproductive strategies," Kruger said. "Men have a greater reproductive benefit than women from having a greater quantity of relationships. If they can leverage their scarcity into attracting multiple short-term partners, they will not have as much of an incentive to settle down."

There are about nine unmarried men for every 10 unmarried women in Birmingham, Memphis, New Orleans, and Richmond-Petersburg, Virginia, Kruger says. Philadelphia, Washington, DC, Baltimore, and New York metropolitan areas are tied for the next region where women are relatively most plentiful. In these areas, about 84 percent of the men aged 20-24 are unmarried. In Las Vegas, San Diego, Salt Lake City, Austin, and Phoenix, there are about nine unmarried women for every 10 unmarried men. In these areas, about 77 percent of the men aged 20-24 are unmarried.

Once those young men hit their 30s, they tend to shift from seeking short-term relationships to entering into committed relationships. That's because when women evaluate partners for short-term relationships they value physical features signaling the kind of genes that would be passed on to potential offspring, which may be the only legacy of men who don't stick around for child rearing. These physical features decline as men age, making it more difficult to lure women into uncommitted relationships.

"You see a complete reversal in the pattern," Kruger said, and thus, proportionately more older men are married when women outnumber men.

So, does this mean that middle aged women in these cities get a break? Not really, Kruger says. The higher marital rates for older men likely benefit women who are substantially younger than their husbands, because older men still prefer partners with higher reproductive potential.

The ratio of men to women has other aspects, as well. For instance, studies have shown that when women outnumber men, hemlines actually rise, overall, as women to do more to physically attract men. Also, the rates of divorce and out-of-wedlock births are higher, and interests in women's rights increases. Surpluses of men tend to be associated with more conservative social norms and restricted roles for women.

The paper "When Men are Scarce, Good Men are Even Harder to Find: Life History, the Sex Ratio, and the Proportion of Men Married," appears in the current issue of the Journal of Social, Evolutionary and Cultural Psychology (http://jsecjournal.com/krugerproof.pdf) and the paper "Male scarcity is differentially related to male marital likelihood across the life course" appears in the current issue of the journal Evolutionary Psychology (http://www.epjournal.net/filestore/EP07280287.pdf). Kruger is a researcher in the U-M School of Public Health.

Thursday, June 4, 2009

Women may not be so picky after all

Women may not be so picky after all about choosing a mate

EVANSTON, Ill. --- Men and women may not be from two different planets after all when it comes to choosiness in mate selection, according to new research from Northwestern University.

When women were assigned to the traditionally male role of approaching potential romantic partners, they were not any pickier than men in choosing that special someone to date, according to the speed dating study.

That finding, of course, is contrary to well established evolutionary explanations about mate selection. An abundance of such research suggests that women are influenced by higher reproductive costs (bearing and raising children) than men and thus are much choosier when it comes to love interests.

The new study is the latest research of two Northwestern psychologists whose well-reported work on speed dating offers unparalleled opportunities for studying romantic attraction in action.

Deviating from standard speed-dating experiments – and from the typical conventions at professional speed-dating events -- women in the study were required to go from man to man during their four-minute speed dates half the time, rather than always staying put. In most speed-dating events, the women stay in one place as the men circulate.

"The mere act of physically approaching a potential partner, versus being approached, seemed to increase desire for that partner," said Eli Finkel, associate professor of psychology in the Weinberg College of Arts and Sciences at Northwestern and co-investigator of the study.

Regardless of gender, those who rotated experienced greater romantic desire for their partners, compared to those who sat throughout the event. The rotators, compared to the sitters, tended to have a greater interest in seeing their speed-dating partners again.

"Given that men generally are expected -- and sometimes required – to approach a potential love interest, the implications are intriguing," Finkel said.

"Let's face it, even today, there is a huge difference in terms of who is expected to walk across the bar to say 'hi,'" added Northwestern's Paul Eastwick, the study's other co-investigator.

The study is forthcoming in Psychological Science, a journal of the Association for Psychological Science.

Three hundred fifty undergraduates were recruited for the study's speed-dating events. In half of the events, the men rotated while the women sat. In the remaining events, the women rotated. Following each four-minute "date," the participants indicated their romantic desire in that partner and how self-confident they felt. Following the event, the students indicated on a Website whether they would or would not be interested in seeing each partner again.

When the men rotated, the results supported the long-held notion of men being less selective. When the women rotated, this robust sex difference disappeared.

The study draws upon embodiment research that suggests that physical actions alter perception. In one such study, for example, participants who were told to pull an unrelated object toward themselves while evaluating Chinese ideographs rated them as prettier than participants who pushed an unrelated object away from themselves while viewing the symbols.

"The embodiment research shows that our physical activity and psychological processes interface in ways that are outside our conscious awareness," Finkel said. "In conjunction with this previous embodiment research, our speed-dating results strongly suggest that the mere act of approaching a potential love interest can boost desire."

The researchers suggest that confidence also may have affected the results. Approaching a potential date increases confidence, which in turn makes the approacher less selective.

The study presents a clear example of how inconspicuous gender norms (having men rotate and women sit) can not only affect the outcome of a study, but also skew the chances of a speed dater walking away with a potential match.

"Our society is structured in gendered ways that can be subtle but very powerful," Eastwick concluded. The study has implications both for companies that capitalize on the business of dating and for researchers concerned with how social norms may affect research.