Dementia has overtaken heart disease as the leading cause of death for Australian women, while the number of fatal drug overdoses has peaked above the levels of the late 1990s heroin epidemic, data from the Australian Bureau of Statistics has shown.

Heart disease remains the leading cause of death overall, causing 12% of all deaths in Australian in 2016, but the rate of death by heart disease has decreased by a third in the past decade while rates of dementia have risen.

“Improvements in treatments and prevention of heart disease have contributed to increased life expectancy, but this has also led to increased deaths from conditions such as dementia which affect predominantly very elderly Australians,” the ABS director of health and vital statistics, James Eynstone-Hinkins, said.

Data released on Wednesday also showed the highest number of fatal drug overdoses since 1999, the height of the heroin epidemic, although the majority of overdoses were attributed to prescription opioids.

“In 2016, an individual dying from a drug-induced death in Australia was most likely to be a middle-aged male, living outside of a capital city who is misusing prescription drugs such as benzodiazepines or oxycodone in a polypharmacy (the use of multiple drugs) setting,” the ABS said.

“The death was most likely to be an accident. This profile is quite different from that in 1999, where a person who died from a drug-induced death was most likely to be younger (early 30s) with morphine, heroin or benzodiazepines detected on toxicology at death.”

Benzodiazepines, a depressant found in anxiety and insomnia medication, was the substance most commonly associated with fatal overdoses and found to be present in 36.7% of acute drug deaths in 2016.

Prescription painkillers, such as oxycodone, morphine, codeine and other opioids, were present in 30% of deaths. Psychostimulants such as methamphetamines, MDMA and speed were present in 20.1% of deaths. Amphetamines are five times more likely to be present at a fatal overdose in 2016 than in 1999.

Heroin was found in 20% of fatal drug overdoses.

Professor Michael Farrell from the National Drug and Alcohol Research Centre said the demographic of those most likely to die from a fatal drug overdose suggested “there’s a big probability that there’s a reasonable number of this cohort that are the ageing heroin-using population”.

There has been a significant increase in the number of drug-related deaths since 2011, coinciding with an increase in the illicit use of prescription medication.

Farrell said Australia should review its guidelines around prescribing opioids.

“What we don’t want to do is end up where the US is with a prescription opioid epidemic,” he said.

Of the fatal drug overdoses in 2016, 22% are believed to be intentional.

Psychostimulant drugs such as methamphetamines and ecstasy had the lowest rate of intentional overdose, and Farrell said an increase in deaths caused by that class of drug was likely due to an increase in use combined with an increase in purity.

Three people died after overdosing on pills drawn from the same “bad batch” of MDMA in Melbourne in January.

The rate of deaths by suicide dropped slightly in 2016 from a high in 2015, but still accounted for 11.7 deaths per 100,000 people.

“It’s a pleasing figure to see that there are fewer deaths by suicide, but it’s still eight deaths a day,” Lifeline director Alan Woodward said. “Behind those statistics are people and in each of those cases there are family members, friends, work colleagues, school communities, who are acutely impacted by death by suicide.”

The Indigenous suicide rate remains twice that of the broader Australian population.

Suicide was the fifth-leading cause of death for Aboriginal and Torres Strait Islander people, behind heart disease, diabetes, chronic lower respiratory diseases and lung cancer. Rates of death were 1.6 times higher for heart disease, 4.9 times higher for diabetes, 2.7 times higher for respiratory diseases and 2.1 times higher for lung cancer.

The overall standardised death rate for Aboriginal and Torres Strait Islander people was 60% higher than non-Indigenous people.

• In Australia, the crisis support service Lifeline is on 13 11 14. In the UK the Samaritans can be contacted on 116 123. In the US, the National Suicide Prevention Lifeline is 1-800-273-8255. Other international suicide helplines can be found at www.befrienders.org.