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Great sex holds the ingredients to heal the
brain damage caused by strokes
or degenerative diseases like Huntington's, a new Canadian study suggests.
The study, published today in the Journal
of Science, shows prolactin, a natural hormone produced after orgasm and
childbirth, stimulates the birth of thousands of new cells in the forebrains
of mice. "The experiment that we did ... suggests that mating itself
may enhance neurogenesis," said study author Sam Weiss, a professor of
medicine at the University of Calgary.
Last year, scientists showed the human
brain makes a faltering effort to heal itself after a stroke by sending new
cells to the damaged area. Dr. Weiss says infusing patients with prolactin
could boost this mechanism.
"Because it can be added directly
into the bloodstream to produce the brain effect, we are preparing to test
how it might help stroke recovery," he said.
If the new cells reach the damaged area
before it scars, the effects of strokes could be reduced. Similar approaches
could someday be used to treat other neurodegenerative diseases, including
Parkinson's and Alzheimer's.
Just over 10 years ago, Dr. Weiss made
newspaper headlines around the world when he discovered the adult brain
contains stem cells, the primitive ancestors of new brain cells. But what
caused these cells to multiply and where they migrated in the brain remained
a scientific mystery.
A few years ago, however, the behaviour
of female mice with an impaired sense of smell offered a clue.
"They seemed to be ignoring their
young," Dr. Weiss says.
Virtually all animals rely on smell, or
olfaction, for sexual attraction and for rearing young.
Humans can distinguish between up to
10,000 different odours, from dung to Chanel No. 5. Smell is particularly
important to mothers. Women with morning sickness suddenly become sensitive
to strong odours, and most mothers rely on smell for recognizing and bonding
with their offspring.
So if new brain cells could be born in
adults, Dr. Weiss suspected it is probably in the olfactory region of
pregnant females. The hunch proved correct.
"We found that during the first week
of pregnancy there was a spike in brain cell production," he says.
The new neurons then migrated to the
olfactory bulb, an area at the front of the brain, where they are necessary
for the adult mouse to remember new odours and to distinguish them from
other similar odours.
Several weeks after conception, the new
growth receded, then spiked again when the mice delivered their offspring.
However, pregnancy was not necessarily
the key ingredient.
When mated with sterile males, the female
mice also produced thousands of new brain cells a week after sex.
"Since there was no embryo, the cause had to be a surge of
hormones," Dr. Weiss says.
The researchers soon zeroed in on
prolactin.
Intriguingly, men also make prolactin
after orgasm. This may explain why the man in the celebrated Viagra
commercial stops to smell the roses after a night of sex -- the number of
scent cells in his brain has doubled. It may also explain why the perfumes
and colognes of lovers often have such deep emotional resonance in their
memories.
"It certainly intrigues one to ask
the question ... might [prolactin] be playing a role in mating behaviours
and in relationships?" Dr. Weiss says.
Creatures with minor differences in their
hormone systems have much different romantic habits. Prairie voles are
monogamous and mountain voles are polygamous. Why the difference? Zoologists
point to a small variation in how the tiny rodents' cells respond to the
hormone vasopressin.
Researchers are also focusing on the
links between smell and brain disease.
For example, one of the first symptoms of
both Parkinson's and Alzheimer's diseases is a loss of olfaction. Scientists
believe if they can increase the population of stem cells in the brains of
such patients, they may reduce the impact of these diseases.
Although new cells normally travel to the
olfactory bulb, they change direction in the event of a brain injury.
"This really holds out the chance
that the brain in adults is plastic enough to make a repair," said
Robert Dempsey, chairman of neurosurgery at the University of
Madison-Wisconsin Medical School.
Researchers are also finding other
promoters of brain cell growth. Last year, a study showed chemicals known as
EGF and FGF improved the ability of mice who suffered strokes to navigate a
maze. However, these chemicals must be injected directly into the brain,
while prolactin can be injected into the bloodstream.
While it may take years for scientists to
unravel the benefits of prolactin, people can safely conduct experiments of
their own. "This just shows what sex therapists have known for
years," said Marianne White, a Chicago sex therapist and author.
"A healthy sex life makes the brain
sharper." - Brad Evenson
National
Post 3 January 2003
Late-life
lovin' indicates
more than just mojo
Declining sexual activity in old age has more to do with
ill health than lack of desire, new research has found.
A wide-ranging study of sexuality and health among older adults in the
United States, published in Thursday's edition of The New England Journal of
Medicine, examines sexual attitudes, behaviours and problems among men and
women between the ages of 57 and 85.
Based on 3,005 participants, the survey found that many men and women
remain sexually active – participating in vaginal intercourse, oral sex
and masturbation – in their 60s, 70s and 80s.
The frequency of sexual activity among the study's cohort was similar to
that reported among 18-to-59-year-olds in a 1992 National Health and Social
Life Survey, the researchers noted.
Sexual activity does decline with age, but that is usually the result of
not having an intimate partner or experiencing problems with physical
health.
“Physical health is more strongly associated with many sexual problems
than is age alone,” said Stacey Lindau, the University of Chicago
gynecologist who led the study. “If you have a partner, the frequency of
sexual activity doesn't change that much across age groups.”
Researchers believe the findings could provide an important incentive for
doctors to discuss sexual activity with their aging patients.
“This is a public-health issue because sexual problems may be a warning
sign or consequence of an underlying health issue,” said Georgeanne
Patmios, of the National Institute on Aging, a partner in the study.
Women with diabetes were less likely to be sexually active, the study
found, and men with the disease often suffered erectile difficulties.
Dr. Lindau said physicians should be aware of this connection, and also
take into account that older men and women may stop taking medication for
other ailments if it negatively affects their sex lives.
“If we regard older people as asexual, we really miss an opportunity to
do important counselling and interventions,” she said.
But few doctors are having those conversations, she said. Of those
surveyed, only 38 per cent of men and 22 per cent of women had discussed sex
with their doctors since the age of 50.
Dr. Lindau would like to see physicians begin asking aged patients if
they are sexually active, how their sex lives are going, or if there is
anything preventing them from having sex.
The most commonly reported reason for sexual inactivity among individuals
with a partner was the male partner's physical health.
“It may comfort people to know that they are not alone in enjoying
sexual activity as they age or in experiencing sexual problems, some of
which could be alleviated with medical attention,” said Dr. Lindau.
The number of older adults engaging in sexual activity may be surprising
for younger generations who prefer to picture their grandparents playing
shuffleboard than pitching woo.
Even among the oldest respondents – those between the ages of 75 and 85
– 54 per cent of sexually active persons reported having sex at least two
to three times per month, and 23 per cent reported having sex once a week or
more.
Fifty-eight per cent of sexually active respondents in the youngest age
group – between 57 and 64 – reported engaging in oral sex within the
past 12 months, as did 31 per cent in the oldest age group.
And over all, 52 per cent of men and 25 per cent of women in a
relationship reported masturbating in the past 12 months, as did 55 per cent
of men and 23 per cent of women who were single.
There were, however, some differences between respondents depending on
gender.
Women were more likely than men to rate sex as “not at all important”
(35 per cent of women compared with 13 per cent of men). Forty-one per cent
of respondents in the oldest age group also characterized sex as
unimportant.
Among those surveyed, more men than women reported having had a sexual
experience in the previous 12 months, but Dr. Lindau said this is explained
by the fact that men tend to have younger partners. This could mean that
more female respondents were widowed, she said, or involved with partners
whose advanced age meant they had more serious health problems.
Linda Waite, co-director of the Center on Demography and Economics of
Aging at the National Opinion Research Center at the University of Chicago,
another partner in the study, said the results will have more relevance as
the number of people over the age of 60 increases.
“The baby boomers are just starting to reach these ages and this will
tell us what older adults experience and how they feel about it,” she
said.
The survey, conducted between July, 2005 and March, 2006, is based on the
responses of 1,550 men and 1,455 women who were asked about social and
marital history, sexual activity and function, and physical and mental
health.
Dr. Lindau said the findings show that older adults retain an interest in
and need for sexual fulfilment, even as sexual experience becomes more
physically problematic.
“It raises the question, what benefits are gained from sexual contact
with one's partner?” she said. “We need to understand that better.”
Sex products for the silver-haired set There are birth control
pills targeted at teens, condoms marketed to college boys and little blue
pills directed at middle-aged men.
But the next big demographic target for sexual products, contraceptives
and libidinal aids could be women over the age of 60, according to
researchers at the University of Chicago.
“When I ask my patients about ways of addressing sexual problems they
are very receptive,” said Stacy Lindau, an assistant professor of
obstetrics and gynecology who led a study of sexuality among older adults
published in today's New England Journal of Medicine.
Her study found that 14 per cent of men between the ages of 57 and 85
reported taking a prescription or non-prescription medication to improve
their sexual function, but only one per cent of women did the same.
As the population ages, Dr. Lindau believes there will be an increased
demand for medical intervention among a population of women who expect to
maintain healthy sex lives well into old age.
Forty three per cent of women surveyed reported low levels of desire, 39
per cent had difficulty with vaginal lubrication, and 34 per cent reported
an inability to climax. The most prevalent sexual problem for men was
erectile dysfunction, a condition that is already addressed by several
products on the market, including the hugely popular Viagra.
Chanelle Gallant, a psychotherapist and manager of Good for Her, a
women-oriented Toronto sex shop, said she believes there is a large market
for sex products aimed at the grey-haired set.
Ms. Gallant said her store has many customers over the age of 60, but
that she expects to see more as the population of baby boomers enter their
retirement years.
“We really make an effort to carry erotic titles, DVDs and books, that
reflect older folks,” she said. “It's not always easy to do. I think
that shift is still to come.”
Dr. Lindau said there are several clinical trials in the U.S. looking for
medical interventions for women, largely focused around libido issues and
vaginal dryness, which can result during changes in estrogen levels
post-menopause.
“We currently do not have any FDA-approved medicine therapies for women
and it would be interesting to see how these data inform research and
development about those issues,” she said. - by Siri Agrell
GLOBE
& MAIL 2007 August 22
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