BOSTON (CBS) – Many diseases and conditions we associate with old age are increasingly showing up at earlier ages.

Katy Meagher of West Roxbury was just 24 years old when she was diagnosed with melanoma. “I felt very alone. It was just one of the more scary things, a real wake up call,” she said. She had to have the cancerous mole removed, which left a significant scar, as well as lymph nodes from under her arm.

Dr. Mark Itskowitz, an internist, said cases like Katy’s are no longer unusual. “I’ve seen patients in their 20s with melanoma. There has been a striking increase incidents,” he said. “We can prevent non melanoma skin cancer with sun screen, but unfortunately, the studies suggest that sun screen doesn’t prevent melanoma. Avoidance of ultra violet radiation is our best strategy to prevent melanoma.”

Many other diseases are now showing up in patients at earlier ages, such as osteoporosis. “When I take women in their twenties and she tells me she had severe low weight . . . then even at a young age they can develop osteoporosis,” Dr. Rick Donahue of Personal Health MD in the Back Bay said.

Alzheimer’s is another disease that can strike young, hitting as early as the 40s. “When someone has early onset Alzheimer’s, it’s not as common but it’s more aggressive,” said Dr. Donahue. “The mind needs to be exercised and we think if it is exercised in a healthy way, it is going to be less apt to have many brain diseases, such as Alzheimer’s.”

Strokes can happen as early as the twenties and thirties. The biggest threat is high blood pressure that goes unchecked. “You can’t feel it. You can’t see it,” said Dr. Donahue. “Being overweight, salt, alcohol, and stress are the four modifiable risk factors.”

Some public health experts now worry that today’s younger generation could be the first to have a shorter life expectancy than their parents. “I am seeing what we used to think of as old age diseases in younger ages,” added Dr. Donahue.

The surge in type 2 diabetes is a perfect example. The good news, according to Dr. Itskowitz, is we have more control over our destiny than we might think. “Lifestyle modification is so important,” Dr. Itskowitz said.