MAYBE PEOPLE’S DIETS CONTAIN MORE L-SERINE NOW: Risk of dementia is declining, but scientists don’t know why.

Dementia is on the decline, with the risk of developing it dropping 20 percent per decade since the late 1970s, according to a striking new study published Wednesday in the New England Journal of Medicine.

It’s a finding that may be hard to believe, with a tsunami of new dementia cases looming in the near future. By 2025, Alzheimer’s disease alone will rob 7.1 million people older than age 65 of their memories, their ability to function, their very personalities — a 40 percent increase from today. The Alzheimer’s Association has predicted that, by 2050, the disease will cost $1.1 trillion.

But both facts appear to be true. The aging of the baby boomers means that dementia cases will surge to an all-time high — the sheer number of older people who are living longer means that even a drop in the incidence of the disease won’t solve that problem, which will exact a huge health and financial toll. But despite the popular perception that getting old invariably means people go gray and begin to lose their memory, the new data strongly suggest that, over the past few decades, the risk of developing dementia has receded for people with at least a high school education, raising hope that it may be possible to prevent one of the scariest risks of aging.

But it’s probably something else, like fewer people smoking. But given my family history, I’ve started taking L-Serine on the off-chance that it might help and isn’t likely to do any harm.