Millions of elderly Americans are becoming highly addicted to anti-anxiety medicines that treat depression, anxiety and sleep issues, a new study had warned.

Figures compiled by the University of Michigan show that one in four older patients who are prescribed the class of drugs known as benzodiazepines never stop using them.

Of the close to 50 million US adults aged 65 or older, about nine percent are prescribed benzos such as Xanax and Valium - more than any other age group - and the rate of use only increases with age.

These drugs are being increasingly scrutinized as drivers of America's addiction epidemic, alongside opioids, as more and more Americans struggle to get off them.

But the Michigan team warn no attention is being paid - by the general public and doctors - to the hardest-hit group: the elderly, who may be reluctant to experiment with less powerful forms of treatment.

Sedatives that treat depression, anxiety and sleep issues may be highly addictive for older adults, a new study has warned (file image)

Benzos, prescribed under names such as Valium and Xanax, are recommended for short-term treatment among older adults because they are easily flushed from the body.

For the study, the team looked at the use of the pills by low-income older adults, who were 78 years old on average, in Pennsylvania.

The participants were part of the Supporting Seniors Receiving Treatment and Intervention (SUSTAIN) program, which helps older adults with drug costs.

Researchers interviewed the adults to check for a variety of mental health issues including depression, anxiety and any sleeping difficulties.

They also calculated a medication possession ratio (MPR) of how many days' supply they had been prescribed to how many days the prescription was valid.

An MPR of 30 percent or more over the course of a year was defined as long-term use.

Close to 600 adults received their first prescription for benzodiazepine between 2008 and 2016 from either primary care physicians or other non-psychiatrists.

The researchers found that around 26 percent of the group still had a current or recent prescription just one year later.

Long-term use was most common among white patients, who were four times more likely to become addicted.

Additionally, the patients who received the largest amounts were the most likely to become long-term users - some had received close to eight months' worth of benzodiazepine.

For every 10 extra days the prescription was written for, long-term use risk doubled.

The National Institutes of Health says the rate of benzos use is highest among older people despite several studies that have shown it increases the risk of car crashes and broken bones.

This is because some of the drugs' side effects include drowsiness and fatigue.

Additionally, a 2014 study published in the British Medical Journal found an association between benzos use in older people and an increased risk of Alzheimer's disease.

Lead author Dr Lauren Gerlach said the rate of adults going on to long-term use is concerning.

'This shows that we need to help providers start with the end in mind when prescribing a benzodiazepine, by beginning with a short-duration prescription and engage patients in discussions of when to reevaluate their symptoms and begin tapering the patient off,' she said.

'We also need to educate providers about effective non-pharmaceutical treatment alternatives, such as cognitive behavioral therapy, for these patients.'

She said that, through interviews, the team found that long-term users were not more likely to have been diagnosed with anxiety or depression but they were more likely to have sleep issues.

However, benzos are not recommended as a replacement for sleep aids because they can cause daytime sleepiness and therefore worsen sleep.

'Since mental health providers see only a very small minority of older adults who have mental health issues, we need to support primary care providers better as they manage these patients' care,' said Dr Gerlach.

'We must help them think critically about how certain prescriptions they write could increase the chance of long-term use.'