More than half of nurses polled for a survey on community nursing say they have missed care in their previous working week.
It was particularly noticeable in relation to health promotion in older people.
March was the worst on record for the number of patients on trolleys in emergency departments, and experts say community nursing deficits are contributing to this.
New research shows that they are so overworked, they are missing out on opportunities to care for their patients.
Dr Amanda Phelan, who carried out the study for UCD, said: "It really indicates a crisis in community nursing.
"And the fact that population health is not being served best because there are lots of preventive and interventions that should be undertaken, but just can't be undertaken due to the pressures that community RGNs and public health nurses are facing on a daily basis."
Mary Leahy, a public health nurse based in Oranmore, Co Galway, said the lack of resources dedicated to community health results in a waste of taxpayers’ money in the long term.
"Because delayed care escalates the level of deterioration, it's invariably going to [result in] the person being sicker and in hospital for longer," she said.
The study estimates that missed care in an older person could have an individual cost of over €18,500, not including nursing home fees of almost €800 a week.
Dr Phelan gave the example of a 75-year-old woman with failing eyesight who falls in her home.
"If you have somebody in that house who is able to advise about the environment, able to ask about that lady's eyesight , refer her on to appropriate professionals, test for diabetes, all of that could be really dealt with a t an earlier point," she said.
One of the main recommendations of the study is that a Commission be established to determine what roles community nurses play in the primary care system.