Aging may not be quite as gradual as it seems.

A new study from Stanford University in California has revealed that there are two periods when aging seems to accelerate.

These two spurts tend to occur around age 44 and again at age 60, the study found.

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In the study, 108 participants ranging from 25 to 75 years old gave blood and biological samples over the course of several years, according to a Stanford University press release.

The researchers analyzed more than 135,000 molecules and microorganisms (bacteria, viruses and fungi), finding that most of them don’t change in a "gradual, chronological fashion."

"We’re not just changing gradually over time; there are some really dramatic changes," said Michael Snyder, PhD, professor of genetics and the study’s senior author, in the release.

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"It turns out the mid-40s is a time of dramatic change, as is the early 60s. And that’s true no matter what class of molecules you look at."

The findings were published in the journal Nature Aging last month.

Dr. Brittany Ferri, a New York-based occupational therapist with the National Council on Aging, agreed that aging doesn't always happen steadily.

"Big changes can happen at certain points in your life," Ferri, who was not involved in the study, told Fox News Digital. "People tend to experience shifts that will impact their health going forward."

In their 40s, people are likely to face more stress or make lifestyle changes that could affect their well-being, and by the 60s, age-related changes will impact the organs and immune system, according to Ferri.

"With aging happening in distinct stages, certain phases will bring noticeable shifts in how the body functions," she added.

These "abrupt changes" can have an impact on people’s health as they age, the study found.

"During your 40s and 60s, key molecules and microbes related to heart health and the immune system change considerably," Ferri told Fox News Digital after reviewing the findings. 

"In your 40s, changes in molecules that affect how your body processes fats and alcohol could raise your risk of heart disease if they’re not managed well," she went on.

"In your 60s, shifts in your immune system can make you more prone to age-related health problems."

The researchers noted that they were not surprised by the shift in the early 60s, as this is a time when age-related diseases and conditions tend to emerge.

The surge in the mid-40s, however, was not expected. While they initially thought this shift was due to menopause or perimenopause in women, they realized it was also occurring for men at that age.

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"This suggests that while menopause or perimenopause may contribute to the changes observed in women in their mid-40s, there are likely other, more significant factors influencing these changes in both men and women," first author Xiaotao Shen, PhD, a former Stanford Medicine postdoctoral scholar, said in the release. 

"Identifying and studying these factors should be a priority for future research."

The main limitation is that these changes could be caused by lifestyle or behavioral factors that tend to emerge in the 40s and 60s, Snyder acknowledged.

Looking ahead, the team plans to conduct further research into these aging spurts.

They also emphasized the importance of healthy behaviors to counteract these changes.

"That could look like increasing exercise to protect your heart and maintain muscle mass at both ages or decreasing alcohol consumption in your 40s as your ability to metabolize alcohol slows," the researchers wrote.

Added Snyder, "I’m a big believer that we should try to adjust our lifestyles while we’re still healthy."

For those in their 40s, it's important to eat healthy, manage stress, and cut back on alcohol to support the changes in metabolism and heart health, according to Ferri. 

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"In your 60s, try to focus on staying active to help boost your immune system and stay at a healthy weight," she recommended.

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The Stanford study was funded by the National Institutes of Health and the Stanford Data Science Initiative. 

Fox News Digital reached out to the researchers for comment.