Age regression is a sexual fetish for some individuals. Individuals with this fetish often enjoy mainstream age regression stories, although there are also specific stories that cater to the fetish and even some pornographic films in which an elderly person becomes a young adult again. Age regression fetish fiction follows several frequent plots, playing on the same themes as mainstream age regression but usually taking it to sexualized extremes. Often, an arrogant, cruel or otherwise errant character is regressed - in other words, "cut down to size". Other times, a character who is unable or unwilling to cope with adult responsibilities will have their adulthood revoked by various means, either forcibly or by choice. In either case, the newly regressed character may be taunted and humiliated, or they may be pampered and babied, sometimes including breast feeding and lengthy diapering scenes. In some stories the character is regressed all the way back into the womb, leading to a related fetish, unbirthing. Sometimes, the age regression is temporary. Other times, the character is stuck as a child or teen and will begin a new life. Occasionally, transgender elements are part of these fetish stories as well, as the characters find themselves not just younger but with a new sex. Aside from the more obviously sexual aspects of fetish stories, they often differ from mainstream age regression stories in other ways. While mainstream age regression or bodyswap stories almost always end with the protagonist returned to normal, in fetish fiction it's more likely for the character to remain stuck in a younger body. Also, while mainstream age regression fiction often features characters turned into blissfully unaware infants (these stories typically concern another character's frantic attempts to turn the person back into an adult), in fetish fiction the regressed characters are rarely fully mentally regressed to an infant's level, as they would lose awareness of what had happened to them. They usually retain at least some of their adult memories, but they now find themselves unable to speak, control their bodily functions, etc. This plays into the fetishist's fantasies of loss of control, while for those without the fetish, the loss of speech and bowel control is generally a horrifying concept. Age-related bodyswap stories are also popular with age regression fetishists.
The age regression fetish typically arises from a desire to escape the stresses of adult life. Some age regression fetishists had happy childhoods they now wish to return to, while others had unhappy childhoods they now want to "do over". While it's mostly an adult fetish, it's not unheard of for teens to have the fetish also. The fetish is generally not well accepted in mainstream society, and age regression fetishists typically keep their desires a secret, often even from their lovers.
The age regression fetish is closely related to the adult baby fetish, but while it can be probably said that all adult babies have an age regression fetish to some degree (in that they enjoy the fantasy of becoming children), not all age regression fetishists are adult babies (in that not all of them are excited by wearing diapers or engaging in other aspects of ageplay.)