There are more than 100 types of dementia, including the well-known Alzheimer's disease and vascular dementia. As described by the royal commissioners, the disease amounts to "a complex and broad set of conditions which can have a devastating impact on people’s lives – those living with dementia, their families, close friends and carers".

By some measures, the disease is already the biggest killer of women. People living with dementia are twice as likely to be admitted to hospital. More than half of people living in residential aged care in 2016 had a diagnosis of dementia.

In 1901, only 4 per cent of Australians were aged 65 or older. By June 2010, this proportion had risen to 13.5 per cent, and is projected to increase to between 21 per cent and 23 per cent by 2041. A massive health challenge looms, for both the ageing generations alive now, and the newcomers, generally from small families, who will provide the workers and the tax revenue to care for their elders.

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Unreliable statistics are a step on the road to undesirable "care". The royal commission has heard many horror stories from the aged-care frontline. Last month The Sydney Morning Herald reported on a study that found people living with dementia in aged-care facilities are being unnecessarily sedated with antipsychotic drugs for more than 200 days at a time, twice as long as the maximum time recommended.

No respecter of rank, dementia's toll has extended from world leaders (Ronald Reagan and Margaret Thatcher), to entertainers (Don Lane, Glen Campbell, AC/DC's Malcolm Young, Charlton Heston), sportsmen (rugby league Immortal Graeme Langlands) and beloved Sydney identities such as publican Doris Goddard. Its toll is not expected to go into reverse any time soon.

One reason Australia conducts a five-yearly census is to best allocate government resources. If Australians cannot rely on accurate statistics on dementia, there can be no proper planning of services. With an accurate picture comes the standard of care we all deserve. It's time to a do a real sample of real Australians.