The NYPD has stepped up patrols in subway stations, reinforcing its transit cops with precinct officers after a spate of slashings this year, police officials said yesterday.

A criminologist described the number of attacks as alarming and said police need to figure out if there is an underlying cause before they can reverse things. Some New Yorkers said the rash of attacks worried them and has made them more aware of potential danger.

Stephanie Ferrera, a 21-year-old student at Hunter College, said she hasn’t stopped riding the trains alone, but is now a bit more nervous when doing so.

“I try not to think about it, but it’s definitely in the back of my mind because of my size,” said Ferrera, who lives in West Harlem. “There’s not much you can do about it; you have to get around.”

Guerlane Bernadeo, 31, said she was reassured by the extra police presence. She stood on the Broadway-Lafayette D train platform, the same station where a woman was attacked last week.

“I haven’t changed any of my habits. But I have noticed that there’s more security so I feel safe,” said Bernadeo, a cosmetics project manager from Freeport, Long Island.

There were six slashings in the subway in January, compared with three for the first month of 2015, police said. One was random; the others followed arguments or were robberies.

“We’ve increased the number of patrols, working more with precinct officers,” NYPD Transit Chief Joseph Fox said. “[We] have plans in place to increase the visibility, more precinct officers on platforms.”

Dozens of straphangers waited on the platform of the 110th Street No. 2 station yesterday, where a 27-year-old man was slashed one day earlier.

The man was attacked after he told a loud, visibly intoxicated woman to be quiet, Fox said. The woman then called her boyfriend, who came down into the station and got into a fight with the man, before apparently cutting him.

The attack followed a random slashing in NoHo on Jan. 25, where a 71-year-old woman was cut on the left side of her face by a man who didn’t say anything to her before lunging. A 21-year-old Brooklyn man was arrested in that attack.

“I’m not afraid, really. You just have to be aware,” said Yelanetzi Nunez, a 29-year-old student from East Harlem. “Some people are dangerous, but there are dangerous people outside the subway too.”

The number of slashings this year in such a short period of time is concerning, said Joseph Giacalone, a retired NYPD detective who lectures at John Jay College of Criminal Justice.

“I think it’s something other than one or two crazy people. It could be something more nefarious,” he said, such as gang initiations. “The likelihood of becoming a victim is very small. However, six in [a month] is off the charts and something everyone needs to be made aware of.”

Officials, on the other hand, said the recent slashings don’t appear to be gang-related or copycat attacks, noting they typically follow disputes.

Police Commissioner Bill Bratton, speaking on “The John Grambling Show” yesterday, called January’s slashings an “aberration.”

“Your chance of becoming a victim is one in a million,” said Fox. “Having said that, our subway transportation system is the heart of our city. It’s also a place where people want to enjoy their commute, and the thought of a crime happening on a subway car can be very intimidating.”

Correction: An earlier version of this story stated that an arrest had been made in the 110th Street subway slashing. No arrest had been made at the time of publication.

(With Rebecca Harshbarger)