Quick summary

Noticeable memory loss doesn't always mean Alzheimer's disease. All adults forget names, lose keys, and can't remember what they walked into a room to retrieve. Although many people reach their 80s and 90s with sharp minds, some forgetfulness is considered a normal side effect of busy, stressed lives and aging bodies.

But there's a degree of the problem that's more serious -- though not severe enough to be defined as dementia. It's a subtle decline in mental ability known as mild cognitive impairment (MCI).

People with MCI can have noticeable trouble with language (including speaking, reading, and writing), reasoning, judgment, and memory. But generally they can manage their daily affairs independently and may not even seem impaired to those who don't know them well. According to the Mayo Clinic, 12 percent of those over age 70 have MCI.