WEDNESDAY, July 30 (HealthDay News) -- If you are single and in your 40s, it might be a healthy idea to get hitched.

A new Scandinavian study found unmarried middle-aged people are more likely to develop cognitive impairment than their partnered counterparts.

But before you head to the chapel, consider a couple of caveats. "One wonders if the association is the other way around," that those destined to have trouble thinking show symptoms decades before and therefore have trouble with relationships, said Dr. Sam Gandy, chairman of the Alzheimer's Association's National Medical and Scientific Advisory Council.

There's even more to consider. Another study, this one from Israel, suggests that ruminating about life could actually protect your brain. If you're alone, then, perhaps you should worry about it.

In the study of partnered and non-partnered people, said to be the first of its kind, Swedish researchers examined 1,449 Finnish people who were questioned in midlife and then again in 1998, an average of 21 years later.

The results of both studies were expected to be released Wednesday at the Alzheimer's Association 2008 International Conference on Alzheimer's Disease in Chicago.

Almost 10 percent of those in the study were diagnosed with some form of cognitive impairment in 1998; 48 had Alzheimer's disease.

Those who lived with a partner in midlife were less likely to be cognitively impaired than all the others (including those who were widowed, single, divorced or separated).

After the researchers adjusted their figures to take into account the effects of factors such as weight, physical activity and education, those with partners still had a 50 percent lower risk of showing signs of senility in later life compared to those who lived alone. Those who stayed single their whole lives had a doubled risk of dementia, while those who were divorced from midlife onward tripled their risk.

It's not clear why being single is riskier for the brain. "Cognitive and intellectual stimulation has been reported to be protective against dementia in general," said study author Krister Hakansson, of the Karolinska Institutet in Stockholm. "Living in a couple means that you are confronted with other ideas, perspectives and needs. You have to compromise, make decisions and solve problems together with someone else, which is more complicated and challenging. It is probably easier to get stuck in your own habits and routines if you live by yourself."

But this theory only partially explains the results since those who were widowed and didn't remarry had a much higher risk of dementia, Hakansson noted.

In the other study, Israeli researchers looked at about 9,000 participants in a multiple-year study of heart disease among male civil servants in Israel.

Those who reported that they were most likely to not "ruminate" about family difficulties in midlife were more likely to suffer from dementia in old age. More than one in five of those who ruminated the least had signs of senility, compared to 14 percent of those who "usually ruminate."

Those who ruminated the most about work difficulties were also the least likely to suffer from dementia.

Why the difference? "One possible explanation could be that some forms of rumination may be associated with effective problem-solving and are a form of cognitive activity," said study co-author Dr. Ramit Ravona-Springer, of the Sheba Medical Center in Ramat Gan. "Cognitive activity has been demonstrated to be associated with decreased risk for dementia."

More information

Learn more about Alzheimer's from the Alzheimer's Association  .

THURSDAY, July 31 (HealthDay News) -- In the past 17 years, there has been an overall decrease in risky sexual behaviors among U.S. teens, a new government study shows.

The rates of having sexual intercourse or multiple sex partners have been dropping, while the use of condoms has been increasing, U.S. health officials reported Thursday.

However, the rates of risky sexual behaviors among some groups, including blacks and Hispanic students, hasn't changed since the 1990s, according to this week's issue of Morbidity and Mortality Weekly Report, a publication of the U.S. Centers for Disease Control and Prevention.

"Progress has been made in the last 17 years in decreasing kids' risk for HIV- and STD-related infections," said study co-author Laura Kann, chief of CDC's Surveillance and Evaluation Research Branch in the Division of Adolescent School Health. "However, despite the positive changes, many students still engage in HIV- and STD-related risk behaviors."

Using data from the CDC's Youth Risk Behavior Surveys, Kann's team looked at sexual behavior among high school students from 1991 to 2007.

During that period, HIV-related sexual risk behaviors decreased. The prevalence of sexual experience dropped by 12 percent, from 54.1 percent to 47.8 percent; the prevalence of having multiple sexual partners decreased by 20 percent, from 18.7 percent to 14.9 percent; and the prevalence of current sexual activity went down 7 percent, from 37.5 percent to 35 percent.

In addition, the use of condoms among sexually active students increased 33 percent, from 46.2 percent to 61.5 percent, Kann said: "All that is good news."

But some groups haven't seen a decrease in risky sexual behavior, Kann added. "For example, black students still have the highest prevalence of sexual experience with multiple sex partners and current sexual activity than any of the other subgroups," she noted.

The prevalence of sexual experience among black students hasn't decreased since 2001, Kann said. "Among Hispanic students, we didn't see any changes since 1991 in sexual experience, multiple partners or current sexual activity," she added.

Among male students, the prevalence of sexual experience and multiple sex partners hasn't gone down since 1997, Kann said. "Current sexual activity didn't change since 1991," she said.

More effort is needed to reach black and Hispanic male students, Kann said. "We really need to focus our efforts on these groups in particular, but not to the exclusion of everyone else," she noted.

Another report in the same publication called for state and local education agencies to encourage schools to provide HIV prevention education. In addition, they should work to increase the number of teachers who teach HIV prevention, the report added.

In 2006, most high schools who participated in the CDC survey said they offered some HIV prevention education. However, few schools taught all the 11 topics covered by the CDC's program, according to the report.

Moreover, schools should have a policy to help protect the rights of students and faculty who are HIV-positive.

More information

For more on HIV/AIDS, visit the U.S. Centers for Disease Control and Prevention.

WEDNESDAY, July 30 (HealthDay News) -- Researchers have uncovered a potential cause for postpartum depression, at least in mice.

According to the study, from assistant researcher Jamie Maguire and lead researcher Istvan Mody, both of the David Geffen School of Medicine at the University of California, Los Angeles, dysregulation of a particular class of proteins called GABA receptors on the surface of certain neurons in the brain may induce post-delivery mood disorders ranging from "baby blues" to postpartum psychosis.

The findings immediately suggest a possible therapeutic intervention, the authors noted. They also provided researchers with a new animal model for studying the biology and treatment of the disease -- a valuable research tool that could accelerate the development of new treatments.

Yet the work was not performed in humans, stressed Dr. Bernard Carroll, scientific director of the Pacific Behavioral Research Foundation in California. Just because these animals appear to suffer from a disease akin to postpartum depression, he said, does not mean the two conditions are identical.

"We have to remember that the model is not the disease," he said.

The results were published in the July 31 issue of Neuron.

The protein at the heart of this study, the GABA receptor (type A), serves an inhibitory role in the nervous system, dampening the effect of excitatory neurotransmitters in response to its substrate, GABA. These receptors can bind to more than one molecule, however, and one particular class of molecules called neurosteroids can modulate the receptors' activity.

Neurosteroids are produced in the central nervous system from steroid hormones such as progesterone. During pregnancy, the levels of reproductive hormones (including progesterone) rise sharply, only to drop to pre-pregnancy levels shortly after delivery. As a result, neurosteroid levels also rise and fall.

Maguire and Mody wanted to see what happens to GABA receptors in the brains of mice undergoing the hormonal swings associated with pregnancy. By comparing virgin, pregnant and postpartum mice, the pair discovered that GABA receptor abundance (and function) falls during pregnancy and then returns to pre-pregnancy levels following birth.

That makes sense from a homeostatic point of view, Maguire explained. For the body to maintain a constant level of GABA receptor-derived inhibition, receptor abundance must stay more or less in synch with neurosteroid levels.

"If you want to maintain a constant level of inhibition, with more neurosteroids, you need fewer receptors," she explained. "After pregnancy, when hormone levels drop off, you need more receptors to maintain that level. If you cannot maintain that level after pregnancy, that's when the disorders manifest."

She and Mody reached that conclusion using mice genetically engineered to lack a particular component of the GABA receptor -- that is, mice that cannot adjust GABA receptor levels in response to changing hormone levels. By comparing these mutants to normal mice, the pair discovered that dysregulation of the normal changes in GABA receptor levels lead to mouse behaviors akin to postpartum depression, such as anxiety and depression, with a concomitant decrease in pup survival.

Treatment with THIP (Gaboxadol), a GABA receptor agonist originally intended to treat sleep disorders, ameliorated these effects in mice containing decreased levels of GABA receptors.

"Our thinking is that postpartum depression, and maybe premenstrual syndrome and premenstrual dysphoric disorder, may be due to impaired trafficking of these [GABA] receptors to the [neural] membrane," Mody said.

The next step, he said, is to determine whether human postpartum depression is caused by a similar defect.

"We don't know if this is the same mechanism in humans, but I think all indications are there," Mody said. "The women that are affected by the disorder, the hormone levels are not changed, they are not different than in unaffected women. So, we are confident that it must be the receptor trafficking mechanism that is affected, because the changes in hormone levels are pretty normal."

Dr. Julio Licinio, chairman of the department of psychiatry and behavioral sciences at the University of Miami Miller School of Medicine, praised the research as "very interesting," particularly its development of a new animal model of postpartum depression, which can aid both research and drug development.

"This is probably the strongest [animal] model I have seen in a long time," he said.

More information

For more on postpartum depression, visit womenshealth.gov.

THURSDAY, July 24 (HealthDay News) -- Since 1996, the life expectancy of HIV patients in developed countries taking antiviral therapy has increased more than 13 years, and deaths have dropped by almost 40 percent, researchers report.

Despite these gains, life expectancy still falls short by some 20 years, compared with people in the general population. Life expectancy among injection drug users and those who start their treatment late is even shorter.

"People on [antiretroviral therapy] can live a fairly long life," said lead researcher Robert Hogg, from the British Colombia Centre for Excellence in HIV/AIDS in Vancouver. "If they are a woman, they can marry and have a child, and see the child grow up. If they're going to school, they can graduate from university, or they can continue to have a full adult life expectancy."

The report was published in this week's special HIV/AIDS issue of The Lancet.

For the study, Hogg's team collected data on 43,355 HIV patients from Europe and North America who participated in 14 studies. Among these patients, 18,587 started treatment in 1996 to 1999, another 13,914 began treatment in 2000 to 2002, and 10,584 started treatment between 2003 and 2005.

During the study period, 2,056 patients died. However, mortality decreased from 16.3 deaths per 1,000 person-years in 1996 to 1999 to 10 deaths per 1,000 person-years in 2003 to 2005. In addition, life expectancy for someone starting treatment at age 20 increased more than 13 years, from 56.1 years in 1996 to 1999 to 69.4 years in 2003 to 2005, the researchers found.

For some HIV patients, life expectancy is even shorter. For example, those who start treatment later in disease progression, life expectancy is 52.4 years, compared with 70.4 years for patients treated early. In addition, life expectancy among injection drug users is also lower at 52.6 years, compared with people who acquired HIV is another way at 64.7 years.

In addition, women had a longer life expectancy compared with men (64.2 versus 62.8 years). This may be due to women starting their treatment earlier, Hogg's group suggests.

"This sort of a mind shift for people, even physicians and researchers, that when you look at this life expectancy for these people is even longer than expected," Hogg said.

Rowena Johnston, vice president for research at the Foundation for AIDS Research, thinks that antiretroviral treatment has transformed HIV/AIDS from an early death sentence to a manageable chronic illness.

"One of the most striking successes of HIV/AIDS research has been the development of antiretroviral therapy that significantly extends the lives of people living with HIV," Johnston said.

Increasingly longer life expectancy is obviously a boon to patients and doctors, but it comes with increased risk of side effects and other difficulties associated with taking these medications for long periods of time, Johnston said. "Clearly, though, the benefits outweigh the risks," she added.

"Longer life expectancies are shifting what has been the traditional portrait of AIDS, such as body-wasting along with numerous rare infections, into a condition that is increasingly associated with some of the manifestations we traditionally think of with older age, like cancers, heart disease, kidney and liver disease, and insulin resistance," Johnston said.

However, Johnston thinks that many HIV patients continue to fall through the cracks. "What we haven't managed to do as well is to increase numbers of people getting tested, so that they find out about their HIV infection early enough to reap these benefits," she said.

More information

For more on HIV/AIDS, visit the U.S. National Library of Medicine.