The good news: Adults between the ages of 50 and 90 are having more sex than ever before, according to a new British study. The bad news? There has been a corresponding rise in HIV, syphilis, chlamydia, and other STDs among these older adults. Here's what you should know about the "dramatic" uptick:

How much more sex are older people having?
Adults 50 and older are having more sex than ever before, according to the Student British Medical Journal. In the U.K., a whopping 80 percent of people in this age range report being sexually active.

What changed?
A couple of things. "Drugs that correct erectile dysfunction in aging men have made sex a reality for many more adults," says Caitlin Bronson at Third Age. Online dating also plays a role. Adults 50 and over are the "fastest-growing" demographic for online dating, notes Britain's Daily Mail, allowing older divorcées or those who have lost their spouses to connect with other singles. 

And the STD rates for older adults have gone up?
Indeed. Twenty percent of the United Kingdom's HIV cases are in patients age 50 and up, up from 11 percent in 2001. There's been a similar uptick in STDs in the U.S. According to the CDC, roughly 2,550 cases of syphilis among adults ages 45 to 65 were reported in 2010, up from 900 a decade earlier. And cases of chlamydia among that group of Americans jumped to 19,600 in 2010, compared to 6,700 in 2000

Why is this?
Unsafe sex. Some older women who can no longer get pregnant may believe contraceptives are unnecessary, notes the Daily Mail, and older men feel may feel that using a condom contributes to erectile disfunction. "You never have to retire from sex," clinical psychologist Judy Kuransky tells CNN. "But you should always behave as the 20- to 30-year-olds do. You need to be cautious." 

Sources: CNN, Daily Mail, Third Age, Web MD