Impairment in the body's internal clock, ultimately disrupting a person's sleep-wake cycle, is just one of the potential symptoms of dementia.

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Even relatively small amounts of light can reset the body's internal clock, so find as dark an environment as possible when traveling.

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Gene Block, a professor of psychiatry and biobehavioral sciences at University of California, Los Angeles, and colleagues found that by middle age, the signal the master body clock in the brain sends out to other internal clocks to help resynchronize the different processes gets weaker.

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