Popping a little blue pill doesn't guarantee that an older man will be happy with his sex life, British researchers report.

Men who take drugs like Viagra and Cialis continue to express more concern and dissatisfaction with their overall sex life, compared with men who don't suffer from erectile dysfunction, according to results of a survey conducted by researchers at the University of Manchester.

These men also are more likely to worry about their erections, orgasms, level of sexual desire and frequency of sexual activity, said David Lee, a research fellow on aging at the university's School of Social Sciences.

"Their sexual function improved, but these men weren't reporting that they were any happier with their sexual relations with their partner," Lee said.

Men taking Viagra-type drugs also were more sexually active and more frequently engaged in sexual intercourse, compared to men without erectile dysfunction, the researchers found.

That raises the possibility that the men who ask for Viagra are more preoccupied with sex and, thus, more likely to be critical of their experiences, said Dr. Landon Trost, a urologist with the Mayo Clinic in Rochester, Minn., who specializes in infertility.

Trost noted that Viagra users were more likely to fret about their sex life than both healthy men and men with untreated erectile dysfunction.

"If you have a full head of hair, you worry less about balding. If you are balding, you are likely to be more concerned about hair loss. If you are completely bald, you probably don't worry about it as much," he said. "That's all we're seeing here, I think."

Researchers surveyed more than 2,600 English men between ages 50 and 87, as part of a national survey on aging that occurred in 2012 and 2013, according to the report published in the International Journal of Impotence Research.

These men were asked specific and detailed questions about their sex life, including whether they were taking an oral phosphodiesterase type 5 inhibitor, or PDE5i -- the class of drugs to which Viagra and Cialis belong.

About 7 percent of men reported using a PDE5i drug to enhance their erections over the previous three months, while 21 percent reported that they had untreated erectile dysfunction.

Nine percent of men using a PDE5i reported that they still had problems with erectile dysfunction, according to the survey.

But four out of five PDE5i users reported the drugs having a positive effect on their sex lives. Still, nearly 30 percent of these men said they remained concerned about and dissatisfied with their overall sex life, the researchers found.

By comparison, only 16 percent of men without erectile dysfunction were concerned about their sex life and 18 percent reported being dissatisfied. In men with untreated erectile dysfunction, 19 percent were concerned about their sex life, and 48 percent were dissatisfied with their sex life, the study noted.

Dissatisfaction did not mean less sex, though. About 97 percent of PDE5i users reported sexual activity within the previous year, compared with 88 percent of men without erectile dysfunction.

About 68 percent of men taking a PDE5i said they had frequent sexual intercourse, compared with 50 percent of men who don't have erectile dysfunction.

Part of the problem may be physical. For example, the men taking PDE5i drugs reported more high blood pressure and diabetes, which are physical ailments that can interfere with the ability to achieve orgasm, the authors noted.

But men who use drugs like Viagra likely may also need help dealing with the mental and emotional aspects of their sex life, said Dr. David Samadi, chief of urology at Lenox Hill Hospital in New York City.

"It's not just the mechanical part of sex you have to treat. Getting at the psychological part also is necessary for many men," Samadi said. "The knee-jerk reaction of prescribing Viagra will not always ensure success."

To that end, urologists and infertility experts should recommend that a man concerned about erectile dysfunction receive some sort of therapy or couples counseling alongside their Viagra prescription, Lee said.

"Clinicians should have a more holistic approach to dealing with erectile problems," Lee said. "The use of these drugs should be part of a broader approach to improving men's sexual health."

Even though this was a British survey, Lee expects that American men are facing the same physical, mental and emotional quandaries.

"My suspicion is we'd see something similar in a survey of Americans, because there are inherent concerns among men who use this drug," he said. "I wouldn't think those concerns would be any different in the United States than in the U.K."