"From our experience in the hospitals, patients would tend to put off elective surgeries," said Dr. Clarence Yeo of the Killiney Family & Wellness Clinic. But he noted, "For emergencies, they will still go."
He tends to see more patients at his clinic with respiratory conditions, such as allergies, over the period.
But the tradition of offerings may be waning somewhat.
Read MoreSingapore Julyexports down, sales to US, China pick up
"In the past, there was more burning around. Almost everywhere you go, you'd see incense paper on the floor, grass, trees and roads. Piles of ashes could be seen along the walking paths too," Linsay Tan, a 22-year-old student, said via email.
While as a child she practiced burning offerings and became a vegetarian for the month, "for the past five years, at least, I don't really celebrate this festival," she said.
Others also noted that the festival isn't as compelling for the younger generation.
"Personally I don't [make offerings], but my parents and the generation before did," Dr. Yeo said. "For the younger generations, they are maybe not so familiar with the festival. It won't make much difference to them."
Read MoreSingapore saleno longer a top draw for tourists
Many may now focus less on superstitious aspects -- such as appeasing angry spirits -- and more on offerings to the ancestors. But Dr. Yeo doesn't expect the festival will vanish.
"In some Asian or Chinese families which are still quite traditional, then the tradition tends to carry on. It's been around for hundreds of years. I don't think it will die off," he said.
Indeed, the success of the 2005 horror film The Maid, one of the offerings of Singapore's small film industry and the recipient of a European film award, suggests the holiday isn't likely to lose too much of its attraction. The film, written and directed by Kelvin Tong, broke the city-state's box office record for horror films on its opening weekend. It follows a Philippine domestic helper as she arrives in Singapore during Hungry Ghost month and makes the mistake of stepping on the ashes of a burnt offering, spurring one of the less-than-benevolent spirits to latch on to her.
Read MoreIs Singapore's income inequality gap narrowing?
Modern Singapore cares enough for its ghosts that Tong revisited them in his 2007 comedy Men in White, although the film was panned by critics.
The gates of hell are set to close on August 24 this year. The final day generally brings a spurt of offerings meant to entice the hungry ghosts back to the other side of the fence.
—By CNBC.Com's Leslie Shaffer; Follow her on Twitter @LeslieShaffer1