Dementia and Alzheimer's disease are now the leading cause of death in England and Wales.
Of the 529,655 deaths registered in 2015, 11.6% were attributed to dementia or Alzheimer's, according to the Office for National Statistics (ONS).
Among those aged 80 or over, dementia and Alzheimer's disease account for 13.7% of deaths among men, and 21.2% of deaths among women.
An ageing population and better diagnosis is thought to have lead dementia and Alzheimer's knocking Ischaemic Heart Disease (when blood vessels become narrower or blocked due to cholesterol deposits) from the top disease.
Ischaemic Heart Disease accounted for 11.5% of deaths in 2015.
However, when the figures are broken down by gender, they show that heart disease is still the leading cause of death for men, while dementia and Alzheimer's disease were certified as the main cause of death among women.
Commenting on the figures, Hilary Evans, chief executive of Alzheimer's Research UK, said: "These figures once again call attention to the uncomfortable reality that currently, no one survives a diagnosis of dementia.
"Dementia is not an inevitable part of ageing, it's caused by diseases that can be fought through research, and we must bring all our efforts to bear on what is now our greatest medical challenge."
The mortality rate for dementia and Alzheimer's has more than doubled in the past five years, figures show.
Meanwhile, improvements in treatment, diagnosis and awareness of other diseases has caused their mortality rates to fall since 2001.
After dementia and Alzheimer's, and Ischaemic Heart Disease, the other most common causes of death are chronic lower respiratory disease (such as Emphysema or Chronic Bronchitis), lung cancer ,and cerebrovascular diseases such as strokes.
Martina Kane, senior policy officer at the Alzheimer's Society, said: "While there remains no cure for the condition, everyone who develops it will sadly still have the disease when they die.
"It is therefore essential that people have access to the right support and services to help them live well with dementia and that research into better care, treatments and eventually a cure remain high on the agenda."
When all forms of cancer are grouped together, the disease was the most common cause of death in 2015, accounting for 27.9% of all deaths.
For people aged under 35 suicide is the leading cause of death.
Meanwhile, breast cancer remains the leading cause of death for women, aged 35 to 49.