There was at least one scientific study, by authors who don't want it used to condemn homosexuality.

Summary: Study at the height of the AIDS death rate found that homosexuality led to shortened lifespan. AIDS death rate has declined dramatically, but there has not been a followup study.

Here's a politifact analysis: https://www.politifact.com/virginia/statements/2012/jun/07/b...

More recently, a 2014 pro-LGBT study claimed to show a shortened lifespan, attributed to prejudice: https://www.medicaldaily.com/can-prejudice-kill-you-lesbian-... though this failed replication ("No effect found") https://www.sciencedirect.com/science/article/pii/S027795361...