Far from the "grumpy old men" stereotype, people may actually become more trusting -- and happier -- with age, a new study suggests.

"When we think of old age, we often think of decline and loss," study co-author Claudia Haase, an assistant professor of human development and social policy at Northwestern University, said in a university news release.

"But a growing body of research shows that some things actually get better as we age," she said. "Our new findings show that trust increases as people get older and, moreover, that people who trust more are also more likely to experience increases in happiness over time."

In the study, Haase and colleagues looked at nearly 200,000 people across 83 countries and found a link between aging and higher levels of trust.

The findings held steady for over 30 years, which suggests that this association is not restricted to certain generations, the researchers said.

"For millennials, generation X, and baby boomers alike, levels of trust increase as people get older," said Haase, who is also director of Northwestern's Life-Span Development Lab. "People really seem to be 'growing to trust' as they travel through their adult years."

Focusing on the United States, they then followed more than 1,200 Americans. Again, people tended to become more trusting as they aged, according to the study.

The findings were published online this month in the journal Social Psychological and Personality Science.

Why the increase in trust with age?

"We know that older people are more likely to look at the bright side of things," Haase said. "As we age, we may be more likely to see the best in other people and forgive the little letdowns that got us so wary when we were younger."

Of course a rise in trust levels has its bad side, sometimes putting older adults at higher risk for scams and fraud.

However, the researchers found no evidence that those negatives detract from the benefits of being more trusting. The positive link between trust and well-being was consistent across a lifetime, the study authors said, suggesting that trust is not usually a liability in old age.

"Our findings suggest that trust may be an important resource for successful development across the life span," Haase concluded.