CHICAGO (CNN) -- The American Medical Association admitted Wednesday its journal failed to disclose that the authors of a sex study had been paid by the maker of the drug Viagra.

A study in Wednesday's edition of the Journal of the American Medical Association reported that a significant percentage of American men and women experienced sexual dysfunction.

The journal did not point out that Edward Laumann, a University of Chicago sociologist and the lead author of the study, and his co-author, Raymond Rosen, had been paid by Pfizer Inc. to review clinical trial data on Viagra before the impotency drug was submitted for government approval.

Laumann was quoted as saying the study "gives us a base for explaining why we had this enormous response to Viagra."

Dr. Phil Fontanarosa, a JAMA editor, said the connection would be noted in a subsequent issue.

"It was an oversight on the part of JAMA," AMA spokesman Scot Roskelley said. "The authors did disclose it, the person who was looking at it just didn't catch it."

The survey found that for millions of Americans, sex isn't so hot.

It found that sexual dysfunction afflicts 43 percent of women and 31 percent of men, with problems including a lack of interest in sex and the inability to have an orgasm.

As grim as the survey's findings are, the results could offer hope to millions, many of whom think they're the only ones having trouble in bed, said Laumann.

"Often they don't even admit it to their partners. It's the old 'I've got a headache' instead of 'I don't feel like having sex,"' he said.

The researchers said problems with sex are often coupled with everything from emotional and health problems to lack of time, job pressures and money trouble. But they said they aren't sure which comes first -- stress or problems with sex.

The researchers based the findings on the 1992 National Health and Social Life Survey, a compilation of interviews with 1,749 women and 1,410 men.

The participants, ages 18 to 59, were asked if they had experienced sexual dysfunction over several months in the previous year. Sexual dysfunction was defined as a regular lack of interest in or pain during sex or persistent problems achieving lubrication, an erection or orgasm.

Lack of interest was the most common problem for women, with about a third saying they regularly didn't want sex. Twenty- six percent said they regularly didn't have orgasms and 23 percent said sex wasn't pleasurable.

About a third of men said they had persistent problems with climaxing too early, while 14 percent said they had no interest in sex and 8 percent said they consistently derived no pleasure from sex.

Overall, 43 percent of women and 31 percent of men said they had one or more persistent problems with sex. Researchers had expected the overall numbers to be closer to maybe 20 percent for each sex.

Researchers said those in the survey who experienced sexual dysfunction often were more likely to be unhappy and more likely to describe their satisfaction with the partnership as unsatisfactory, Laumann said.

The Associated Press contributed to this report.