NEW YORK (Reuters Health) - As people age, they experience shrinkage in the part of the brain responsible for inhibiting appropriate behavior -- which may explain why your great-aunt asks embarrassing questions about your weight and older people seem to have fewer qualms about making racist remarks than younger individuals do, an Australian researcher suggests.

Other consequences of atrophy in this brain region, known as the frontal lobes, may include a greater risk of depression and a tendency toward problem gambling, according to Dr. William von Hippel of the University of Queensland.

In the October issue of Current Directions in Psychological Science, von Hippel reviews research on how changes in executive function, or the ability to plan and control thoughts and actions, may negatively affect older people's behavior.

Studies have shown that older people tend to be more prejudiced than younger individuals, von Hippel notes, but this may be because they are less able to muffle the "automatic or unintentional stereotypical thoughts (that) appear to be common in most people." In fact, he adds, tests of the ability to ignore distraction found that the worse an older person's ability to focus, the more likely they were to express prejudice.

Older people also are more likely to exhibit "off-target verbosity," von Hippel points out, or talking a great deal about topics unrelated to the current conversation. Research suggests that adults of all ages rely on their ability to inhibit inappropriate comments to interact with others socially, he notes, while older people may begin to lose this ability. This could explain their greater likelihood of asking about private topics in public situations, he said.

Similar loss of function could put older people at greater risk of becoming depressed, he adds; for many people, the ability to control "rumination," or brooding about problems without doing anything to solve them, is a key mechanism for avoiding depression, and if this ability is lost with age, the risk of depression may increase.

Tests of brain function found that among people with late-onset depression, loss of inhibition was linked to increased rumination, but the relationship wasn't seen among older people with early onset depression.

Similarly, von Hippel writes, not everyone faces an increased risk of becoming a problem gambler with aging, but individuals who have struggled throughout their lives to control their tendency to gamble may be at risk. He and his colleagues have demonstrated that among impulsive older gamblers, executive function and problem gambling are linked, but the link does not appear in less impulsive older people.

Older people show stronger executive function earlier in the day, he notes, so one way of coping with the social effects of frontal lobe atrophy could be to encourage them to schedule important activities for the morning hours. Both aerobic exercise and caffeine consumption could also boost executive function among older adults, he adds.