IT IS WELL KNOWN that the pandemic has been especially dangerous for people already suffering from conditions such as heart disease, respiratory problems, diabetes and so on. But government statistics show that the most common pre-existing condition among those who died from covid-19 in England and Wales in March and April was not a physical ailment at all. It was dementia, which 25% of the deceased had been living with. Something similar is presumably true in other countries, but Paola Barbarino, chief executive of Alzheimer’s Disease International, an advocacy group, complains that data are scanty. Only Britain and Italy have produced detailed figures, making analysis difficult, and hampering efforts to prepare for any second wave of the pandemic.
That so many people who have died from covid-19 had dementia is partly because both conditions disproportionately affect the elderly and partly because care homes, where many people with dementia live, have been so ravaged by the virus. But the high death rate also reflects the difficulty many people with dementia have in taking hygienic and social-distancing precautions. And the isolation and broken routines that lockdowns have brought have made dementia worse for many. They have hastened the cognitive decline that social interaction can help arrest, and made it harder for families, friends or professionals to provide care. So the number of deaths ascribed to dementia itself has also climbed sharply during the pandemic.
All this is depressing enough for those touched by dementia—including an estimated 50m globally who have the condition (a number expected to rise to 80m by 2030 and 150m by 2050 as the world ages) and their families, friends and carers. Equally depressing is the prospect that the condition has fallen further down the list of health-care priorities during the pandemic. The continuing hunt for a cure and a vaccine for covid-19 will suck resources away from research into the causes and pathology of dementia—which also resembles the coronavirus in that there is no cure and no vaccine.
So news of advances in the understanding of dementia—and of how to mitigate, delay, diagnose and perhaps even cure it—are rare chinks of light in the gloom. Dementia has many causes, of which much the most common is Alzheimer’s disease. And the Alzheimer’s Association International Conference (AAIC), which wound up on July 31st, heard some reasons for hope.
Perhaps the most striking report presented was from the Lancet Commission on dementia prevention, a panel of experts commissioned by the British medical journal, which suggested that as many as 40% of dementia cases might in theory be delayed or prevented by tackling 12 “modifiable” risk factors. This builds on decades of research showing the links between some behaviours and physical conditions and the risk of developing dementia. It has long been known, for example, that, most obviously, a career involving a lot of pummelling to the head, such as boxing or football, increases the risk. So do smoking, high blood pressure, obesity, hearing loss, a low level of education and diabetes. But many experts had put the percentage of dementia cases deriving from such risk factors lower, at 30%. And the new research added three new risk factors: excessive drinking in middle age; head injuries, also in middle age; and exposure to air pollution in later life.
Already there is evidence in some rich countries that the age-specific incidence of dementia is declining, even as the overall prevalence increases as societies get older. New public-health campaigns to counter the pandemic, which will involve tackling many of the same risk factors, are likely to strengthen this trend. Some relatively simple interventions—such as ensuring the hard-of-hearing have access to, and wear, hearing-aids—can make a difference.
One reason why dementia is so hard to treat is that, when it is detected, it is often quite advanced. At present diagnosis normally involves cognitive testing backed up by a number of physical tests. A genetic predisposition to Alzheimer’s can be gauged from a blood test, but to spot the presence of the disease, through the build-up of two characteristic proteins in the brain, requires a lumbar puncture, to examine a person’s cerebrospinal fluid, and a scan of the brain itself.
So another announcement at the AAIC caused some excitement. This was of a simple blood test that could both distinguish between Alzheimer’s disease and other neurodegenerative conditions, and spot those at risk years before symptoms appear. It measures a particular form of one of the proteins, tau, called p-tau217, and was found to predict Alzheimer’s with 96% accuracy.
Earlier in July optimists had been cheered by the news that Biogen, an American firm, had applied to the Food and Drug Administration for approval of a drug called aducanumab. The firm says that, in trials among people with mild cognitive impairments or an early stage of Alzheimer’s, the drug had produced “significant benefits” in some of them on measures of cognition and function such as memory and language and in “activities of daily living”.
Many working in Alzheimer’s research remain sceptical on both counts. Potential blood tests have been hailed before but not achieved the accuracy needed to be clinically useful. And Biogen itself ended clinical trials of aducanumab in March last year because of what it then saw as disappointing trial results, only to resume them in October after a fresh look at the data. And, even on the most optimistic assumptions, neither the diagnostic test nor the therapy will be available for months or even years. To anxious carers worried about how to protect people with dementia from the prolonged danger of coronavirus, they have little hope to offer.