Alzheimer’s disease may be inherited more often than previously known, according to a new study that paints a clearer picture of a gene long known to be linked to the common form of dementia.

The authors of the study, published Monday in the journal Nature Medicine, say that this might even be considered a distinct, inherited form of the disease and that different approaches to testing and treatment may be needed.

Among people diagnosed with Alzheimer’s, researchers recognize familial forms of the disease and sporadic cases. Most cases are thought to be sporadic, which develop later in life. Familial forms, caused by mutations in any of three genes, tend to strike earlier and are known to be rare, accounting for about 2% of all Alzheimer’s diagnoses, or about 1 in 50 cases.

Under the new paradigm, 1 in 6 cases of Alzheimer’s would be considered to be inherited, or familial.