Longevity doesn't just mean living longer. It means living differently.

The longer people live, the more their careers resemble winding roads instead of straight lines, according to longevity expert Andrew Scott.

Scott has experienced this roundabout route first-hand. An economics professor at London Business School, Scott spent the first half of his career lecturing on business cycles, monetary policy and fiscal policy. His evolution from plain-vanilla economist to leading expert on aging and longevity began mid-career.

"I was teaching a course on big issues for the world economy," Scott explains. "I would give a talk about an aging society, and I realized something was missing."

Emerging data on aging showed that people were living longer, healthier lives—which to Scott seemed like a wonderful thing. "It meant fewer parents snatched away mid-life. It meant more grandparents, even great-grandparents, meeting their grandchildren," he says. Yet the prevailing research around aging had turned living longer into something profoundly negative: "It was like, 'Oh, look at all these old people, we can't afford them; they get ill, they have a pension, this is a crisis.'"

Where others saw crisis, Scott saw an opportunity to reimagine how modern humans find meaning in longer lives—a concept that became the basis for his 2016 book, The 100-Year Life, co-written with London Business School colleague Lynda Gratton. The bestseller explored what our life paths will look like—and how we will support ourselves financially—as more of us live into our 90s and beyond.

Scott, the newest fellow at the TIAA Institute, recently sat down with the Institute's head, Surya Kolluri, for a wide-ranging conversation on longevity. Below is an excerpt, edited for brevity and clarity.

Surya Kolluri: What's been the most surprising thing you've learned about aging?

Andrew Scott: That aging is malleable. Research is always ongoing, but it looks like only 20% of how we age is pinned down by genetics, which means the rest is therefore luck or environment or your behavior. So more and more of healthcare is going to be outside of hospitals. It's about what we eat, how we exercise, how we sleep. We are seeing a whole bunch of new products and new providers aimed at our health outside of the hospital system.

Kolluri: One of the themes of your book is that as people live longer, we'll shift from a traditional three-stage life—education, work and retirement—to a multi-stage life. Can you elaborate on what this means?

Scott: The three-stage life has a very simple financial model. You get your education, then you start work, then you retire. Retirement happens at roughly the same age for everyone, so everyone needs roughly the same financial advice and holds roughly the same portfolio.

But in the multi-stage life, the accumulation and decumulation pattern is much more complicated. You could spend your 20s studying or traveling or doing a start-up, and then focus on making money later—or you could flip it around. You might have to take a break from work in your 50s to look after someone who is ill, so then you'll decumulate. Then hopefully, you can go back to work, and you'll be accumulating again.

Kolluri: As you know, TIAA serves a lot of educational institutions. What do higher education institutions need to do to support education across a longer lifespan?

Scott: If we're working longer, we're going to need more education. And if you superimpose onto that some of the technology trends that are happening, it reaffirms the need for lifelong learning. Who provides it? One option is 100% colleges and universities. They are obsessed with age 18 to 23, but as more and more people from older categories need education, there is an enormous market to expand into. But it can't just be a three-year degree at age 50, because that's going to be very expensive. There's plenty of scope for new providers and new products to cover a whole spectrum of options, including bite-size education. Maybe you're working in a new role, and you just need to update your skills. There could be something you do online for a sort of micro-credential course.

Kolluri: Thank you very much for joining us, Andrew.