Aging hits us in our 40s and 60s. But well-being doesn’t have to fall off a cliff.

For the study, Michael Snyder at Stanford University and his colleagues collected a vast amount of biological data from 108 volunteers aged 25 to 75, all of whom were living in California. Their approach was to gather as much information as they could and look for age-related patterns afterward.

This approach can lead to some startling revelations, including the one about the impacts of age on 40-year-olds (who, I was horrified to learn this week, are generally considered “middle-aged”). It can help us answer some big questions about aging, and even potentially help us find drugs to counter some of the most unpleasant aspects of the process.

But it’s not as simple as it sounds. And midlife needn’t involve falling off a cliff in terms of your well-being. Let’s explore why.

First, the study, which was published in the journal Nature Aging on August 14. Snyder and his colleagues collected a real trove of data on their volunteers, including on gene expression, proteins, metabolites, and various other chemical markers. The team also swabbed volunteers’ skin, stool, mouths, and noses to get an idea of the microbial communities that might be living there.

Each volunteer gave up these samples every few months for a median period of 1.7 years, and the team ended up with a total of 5,405 samples, which included over 135,000 biological features. “The idea is to get a very complete picture of people’s health,” says Snyder.

When he and his colleagues analyzed the data, they found that around 7% of the molecules and microbes measured changes gradually over time, in a linear way. On the other hand, 81% of them changed at specific life stages. There seem to be two that are particularly important: one at around the age of 44, and another around the age of 60.

Some of the dramatic changes at age 60 seem to be linked to kidney and heart function, and diseases like atherosclerosis, which narrows the arteries. That makes sense, given that our risks of developing cardiovascular diseases increase dramatically as we age—around 40% of 40- to 59-year-olds have such disorders, and this figure rises to 75% for 60- to 79-year-olds.