No one has yet determined exactly how to light up the brain's passion centers. But research shows that couples feel more attracted to one another after they've engaged in novel, challenging activities—like being tied together in a three-legged race—than after taking part in a routine pleasurable activity like sharing an ice-cream sundae. Fisher says it probably has something to do with challenge that causes a surge in dopamine. Rock climbing isn't necessary; Aron and his wife recently found it quite arousing to go to a bar for the first time in 10 years. "It was challenging for us just to walk in and figure out what to order," he says. Making it a point to celebrate good things together, like job promotions or prestigious awards, also has been shown to fuel passion, probably because of that shared dopamine surge. Practice helps, too. "Any kind of sexual stimulation drives up dopamine in the brain," Fisher explains, "and orgasms release oxytocin to trigger feelings of deep attachment."
Still, as baby boomers heading into their 60s are just beginning to realize, Mother Nature makes them feel less driven for sex when reproduction is no longer on the agenda. Testosterone levels naturally decline in both men and women, making them feel less in the mood, and less often. And common middle-age medical problems like diabetes, enlarged prostate, and heart disease can disrupt blood flow to sex organs, making it difficult for men to achieve and maintain erections even with Viagra or Cialis. A host of medications, too, can interfere with sexual functioning.
Prostate cancer treatments, which can permanently damage nerves that cause erections, present the biggest challenge in terms of robbing men of their sexuality. "At best, Viagra helps about half of those with no function," Morgentaler says. But perseverance can pay off. "Susan," 65, a writer in Manhattan who prefers to remain anonymous, donned "black lace teddies and stiletto heels worthy of a 20-year-old" and initiated oral sex twice a week for several years after her husband's prostate surgery. "At first, he looked at me hopelessly," she recalls, "trying to get to that place where his libido had been. Last year, we were finally able to have intercourse again."
For women, the plunging estrogen levels that occur during menopause often lead to vaginal wall thinning and dryness, which can make sex uncomfortable or downright painful. Menopausal mood swings can also be a mood killer. Susan has had to contend with both of these problems but worked with her doctor to find solutions; they opted to slowly lower her dose of hormone replacement therapy instead of her going cold turkey, for example, and she experimented with different over-the-counter lubricants. But many women are uncomfortable broaching the subject of sexual difficulties, and more than 90 percent of doctors don't ask, according to a 2007 survey conducted by the Women's Sexual Health Foundation.
Speak up. "Most gynecologists say they have very little training in the area of intimacy and sexual function," says Lisa Martinez, the foundation's executive director, "yet women expect these doctors to take the lead." After being treated for breast cancer last year, Martinez, 53, initiated conversations with her doctors about her mastectomy scar, vaginal dryness caused by an antiestrogen drug, and the extreme fatigue she felt from chemotherapy—all of which put a big damper on her sex life. She included her husband in these discussions to put him at ease.
Among the best concrete ways to extend a pleasurable sex life: Stay in peak form as long as possible. "I suspect just as good sex promotes good health, good health promotes good sex," says gynecologist Stacy Tessler Lindau, whose findings in the University of Chicago study showed that diabetics, for instance, were more likely to experience lack of pleasure or difficulty maintaining erections. The study also found that a man's physical health was the most common reason couples gave up. Sexually transmitted diseases can lead to painful intercourse and lubrication problems years later, according to a study published last month in the Journal of Sexual Medicine. Beyond the obvious—practicing safe sex—McCarthy recommends such healthful lifestyle habits as keeping regular sleep patterns, maintaining a healthy body weight, and following a nutritious diet of whole grains, lean protein, and fruits and vegetables. Plus, avoid excess alcohol, known to interfere with sexual function, and exercise regularly to improve blood flow and increase energy.