Heroin remains the drug of choice for WA's injecting drug users, with just under two-thirds of users reporting the drug as "very easy" to get.
Deputy director of the National Drug and Alcohol Centre at Curtin University Simon Lenton said the average age of the illicit drug users had been increasing in recent years.
In 2009, the mean age of those users sampled was 35, increasing to 37 in 2010, 40 last year and 41 this year.
"The sample we're accessing is a group that is getting older," Professor Lenton said.
Seventy-four per cent of the illicit drug users named heroin as the drug of choice.
Professor Lenton said heroin availability had been increasing since the heroin shortage of 2000-2001, but purity was not increasing at the same rate and was "patchy" at best.
This year's sample recorded 59 per cent of respondents suggesting heroin was very easy to obtain, with only 6 and 3 per cent respectively telling researchers it was difficult or very difficult to obtain.
More than a third of users said current purity was medium, with 30 per cent suggesting it was low.
"Purity is nothing like we saw in the heroin glut prior to 2001," Professor Lenton said.
Figures released by WA Police in September showed 22 people had died from a suspected drug overdose this year and 14 of those deaths were suspected to be from heroin.
WA recorded the highest percentage nationwide of users driving after taking an illicit drug, primarily either heroin or cannabis.
The extent of their drug use was not recorded.
For the year to September 7, WA Police charged 331 people for driving while impaired by an illicit drug, up from 153 last year.
After difficulties bringing together a sample of ecstasy users last year for a related study, WA researchers recruited 25 people this year from regular psychostimulant users in addition to 65 regular ecstasy users.
Professor Lenton attributed the problem with recruiting to the low availability of ecstasy in WA.
Only 12 per cent of people sampled in WA used ecstasy on a weekly or more frequent basis in comparison with the national average of 27 per cent.
The figures from the Illicit Drug Reporting System and Ecstasy and Related Drug Reporting System will be presented to a national drug conference in Sydney today.