Terry McDermott, who penned that great series on neuroscientist Gary Lynch earlier this year, has written another illuminating article on Alzheimer’s. The news is bleak: scientists have yet to understand the disease. In fact, we still don’t even know what causes the cellular degeneration in the first place:
It’s been 101 years since Alzheimer’s disease was first theorized, and 30 years since the federal government began funding research on it, spending, to date, more than $8 billion. Private industry has spent billions more. What has been learned?
The answer is perplexing. There have been more than 35,000 scientific papers published on Alzheimer’s just in the last decade. They include hundreds of impressively detailed descriptions of purported disease mechanisms. But in all that wealth of information, there are some rather obvious gaps.
For example, the leading hypothesis of the cause of Alzheimer’s, called the amyloid hypothesis, is centered on the overproduction, or inadequate clearance, in the brain of a protein called beta amyloid. Fragments of the protein aggregate into clumps called plaques. These plaques were first observed more than a century ago by the man after whom the disease is named, Alois Alzheimer.
For most of the century since, scientists have believed the plaques were associated with the disease. But to date, they don’t know whether amyloid plaques are the cause of the disease or a result. They don’t know whether they are vital to the progress of the disease or incidental. They don’t even know whether their presence is indicative of the disease.
A rival idea, called the tau hypothesis, is no more definitive. Where beta amyloid generally aggregates outside brain cells, the protein tau aggregates into fibrous structures, called tangles, inside the cells.
The processes by which either amyloid or tau cause brain cells to malfunction, and in some cases die, are neither well understood nor completely coincident with observations of the disease itself.
It’s now been almost a decade since the decade of the brain, and while we know more than ever about the three pounds of gelatinous flesh inside our head, the lack of scientific progress on major brain diseases has been humbling. Prozac, a drug invented fifty years ago by accident, remains our most effective treatment against depression. Nobody really knows what causes schizophrenia, or if schizophrenia is even a single disease. We have no idea what triggers Parkinson’s. Alzheimer’s remains poorly understood. Autism is a mystery. The list goes on and on. Perhaps one day we’ll be able to fix the brain and prevent its breakdown. But I’m not holding my breath.