The Food and Drug Administration (FDA) plans to loosen the rules for approving new treatments for Alz­heimer’s disease.

Drugs in clinical trial would qualify for approval if people at very early stages of the disease subtly improved performance on memory or reasoning tests, even before they developed any obvious impairments. Companies would not have to show the drugs improved daily, real-world functioning.

For more than a decade, the only way to get Alzheimer’s drugs to market was with studies showing they improved a patient’s ability to function in daily activities.

The plan, published in The New England Journal of Medicine, could help millions of people at risk of developing the disease by speeding the development and approval of drugs that might slow or prevent it.

The change could also be a boon for the pharmaceutical industry and researchers. They often have felt stymied by regulations that left them uncertain of how to get drugs tested and approved for people early in the course of the disease.

The FDA would require firms to study the drugs after they are on the market to show they benefit patients. But these studies might not be randomized clinical trials and so would not be as rigorous as the studies that led to approval.