Step one should be a checkup. Mild cognitive complaints often stem from high blood pressure or chemical, hormonal, or metabolic imbalances. A few simple blood tests can detect most of those, including problems with the liver, kidney, or thyroid; abnormal blood sugar or blood sodium levels; iron or vitamin B12 deficiency; or, rarely, an infection. More profound dementia may stem from a serious but potentially treatable condition such as an abnormal buildup of brain fluid or a narrowing of blood vessels leading to the brain.

In fact, cognitive effects are an underappreciated consequence of many physical ailments. British researchers last year found, for example, that chronic pain makes it more likely that people will forget appointments, bills, and other responsibilities. So detecting and controlling physical problems may help provide better mental focus.