Those momentary memory lapses that typically accompany aging may not be so normal after all. A new study links common forgetfulness in old age to strokes and Alzheimer’s disease.

Researchers at Rush University Medical Center in Chicago studied the mental acuity 354 Catholic nuns, priests and brothers for 16 years. Autopsies conducted after their deaths revealed that brain lesions caused by abnormal proteins and neurofibrillary tangles were present among all the participants who showed even mild or moderate mental decline during the study. These proteins and tangles are hallmarks of Alzheimer’s disease. Researchers also noted evidence of stroke in all those with mild or moderate mental decline.

The good news, according to researchers, is that the mild memory lapses associated with old age did not predict the development of Alzheimer’s. They also did not correlate with dementia at the end of the study. Also, not all participants had the same level of lesions. This suggests there could be other causes for mental decline in the years before death. The report appears in the Sept. 15 issue of the journal Neurology.