Police officers and sheriff’s deputies in Colorado are increasingly under physical attack, according to new crime statistics, and they blame a number of factors.

A swelling population, an overall increase in crime, more interactions with the mentally ill, rising drug abuse and growing hostility toward police are among the reasons for the increase in assaults cited by law enforcement.

“It’s layer upon layer,” said Steve Johnson, chief deputy at the Douglas County Sheriff’s Office. “They just contribute to a volatile situation in which law enforcement officers are the first line of defense. They have to go in and address those things.”

Assaults against Colorado law enforcement officers increased nearly 42 percent between 2012 and 2016, according to the Colorado Bureau of Investigation’s annual crime report, which was released Wednesday.

“I do feel like with what has been going on across the nation the last several years there are more people who are willing to be resistant to police,” said Alamosa Police Chief Duane Oakes, the president of the Colorado Association of Chiefs of Police.

The rising number of assaults against officers comes as Colorado’s overall crime rate is increasing too. In 2016, Colorado’s overall crime rate rose 3.4 percent per 100,000 people, the CBI reported.

The rising overall crime rate was blamed, in part, on the state’s fast-growing population. And some believe increasing altercations with police go hand in hand with increasing levels of crime.

“When crime goes up, assaults on police officers go up,” said Sgt. Bob Wesner, president of the Aurora Police Association.

In 2016, 1,172 Colorado officers were assaulted and 641 were injured, the CBI’s Crime in Colorado 2016 report said. In 2012, 827 officers were assaulted and 511 were injured, the report said.

CBI data on law enforcement assaults relies on statistics reported by 244 agencies in the state. However, not every agency collects assault data, including the Aurora Police Department. And the data compiled relies on officers to fill out reports, which some don’t do if they believe the attacker had no ill intention. For example, an officer might shrug off a push or slap from a person struggling with mental illness or dementia.

In 2016, a few especially violent attacks against officers made headlines: Douglas County sheriff’s Det. Dan Brite was shot in the chest while responding to a report of a suicidal man, and Aurora Officer Eric Ortiz was shot in the face while approaching a suspect after reports of domestic violence.

But most officers are attacked in less lethal ways.

In the assaults that were reported in 2016, most of the officers — 830 — were hit, kicked or punched, and the attacks often occurred as officers were responding to disturbances, attempting arrests or handling prisoners, according to the CBI report.

Last month, the Aurora Police Association, the union that represents rank-and-file officers, awarded an officer for his actions in an assault that never made headlines, Wesner said.

Officer Hayden Jonsgaard encountered a man who was high on drugs and was combative with officers, who tried to shock him with a stun gun. But the man continued to resist and tried to choke Jonsgaard, who had to fight to free himself, Wesner said.

“That’s a prime example of an assault on a police officer that people don’t know about,” he said. “The public hears about them when the assaults involve guns or knives and officers are severely injured.”

In Denver, there were 183 assaults on officers in 2016, a 74 percent jump in five years, according to data on simple and aggravated assaults provided by the department.

“Assaults on police officers are just unacceptable, and it’s disheartening that officers are being killed and injured while working to protect their communities,” the department’s public information office said in an emailed statement.

The statement also said it’s impossible to prevent all assaults, but the police department does all it can to help officers resolve dangerous situations.

Frank Gale, executive director of the Colorado Police Officers Foundation and a spokesman for the Colorado Fraternal Order of Police, said even minor assaults take a toll on departments through lost manpower and the trauma that can eventually lead to post-traumatic stress disorder.

The foundation increasingly is asked to provide services to officers to help them cope with the job, he said.

The FOP does not collect data on assaults, but Gale said members talk about the violence.

“People are more confrontational when they’re encountered by law enforcement,” Gale said. “They’re more uncooperative and more resistant and act out more violently.”

More and more police departments are giving their officers crisis intervention training to help them navigate the volatile situations they encounter with people suffering from mental illness, Oakes said.

It’s necessary for law enforcement agencies to improve community relations to help reduce attacks on officers. People are less likely to resist when they know and trust the officers, Oakes said.

While assaults against officers are on the rise in Colorado, the number of officers killed while on duty remains relatively low.

In 2016, three Colorado officers were killed in the line of duty compared with four in 2015 and one in 2014. Line-of-duty deaths include officers killed in car wrecks and from assaults or medical problems that are related to work.

No Colorado law enforcement officer had been killed in the line of duty this year as of June 30, although the number of officer deaths has increased nationally, according to a report released Thursday by the National Law Enforcement Officers Memorial Fund.

Sixty-five federal, state and local officers were killed on the job across the U.S. during the first six months of 2017, compared with 50 during the same period last year, the report said. Of the 65 deaths this year, 26 were killed in traffic accidents, 23 were killed by gunfire and 16 died of other causes such as suffering cardiac arrest on the job, stabbings, drownings and three who died as a result of illnesses contracted during the 9/11 rescue efforts.