The offspring of Alzheimer’s patients are more prone to developing their own memory problems earlier in life, according to new research from the Boston University School of Medicine.

Middle-aged study subjects all carried the gene APOE-e4, which is strongly associated with Alzheimer’s disease. One group had at least one parent with Alzheimer’s, while the other group carried the gene but had no history of the disease in their family. The group with a family history of Alzheimer’s performed much worse on visual and verbal memory tests; researchers called the difference in memory between the two groups “surprising” — like comparing 55-year-olds to 70-year-olds.

While the group with a family history of Alzheimer’s performed poorly on the memory tests, researchers say their cognitive abilities were still well within a normal range. And though APOE-e4 is only implicated in roughly 50% of Alzheimer’s cases, researchers say this new knowledge could help determine when Alzheimer’s truly sets in and when the most effective time to begin treatment of the disease would be.