TUESDAY, April 28 (HealthDay News) -- Among older adults, the better they're able to read, understand and use health and medical information, the happier they are, suggests a U.S. study.

Researchers asked 383 people 50 and older if they could read and answer questions on medical forms without assistance. They also asked them to rate their level of happiness.

Participants who had the most difficulty reading and understanding medical forms were more than twice as likely to report being unhappy as those with higher literacy levels, the study found.

This finding might have to do with a sense of control, explained lead author Erik Angner, an assistant professor of philosophy and economics at the University of Alabama at Birmingham. Feeling in control -- which could be undermined by poor health literacy -- has been linked to higher happiness scores.

The researchers suggested that improving health literacy should be a critical part of programs designed to boost health among older adults.

The study was published online in the journal Social Indicators Research.

About 90 million Americans have problems understanding and using health information, according to a 2004 Institute of Medicine report.

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