Investors are pouring money into health startups that aim to beat aging.

While some companies focus on creating drugs for age-related diseases like Alzheimer's and Parkinson's, others aim to address the more visible components of aging, such as muscle loss and skin health.

But regulators have yet to define aging, meaning the path to treatments remains hazy.

Progress is nevertheless being made, several executives told Business Insider. Here's what you should know.

Investors are pouring money into health startups that aim to beat aging.

There's just one small problem.

Health regulators, including the US Food and Drug Administration, have yet to define aging as a medical condition. In and of itself, growing old is not an illness in need of treatment. Rather, it is a set of still poorly understood ailments that crop up in old age — from diseases like Alzheimer's and cancer to conditions like muscle decay and hair loss — that can dramatically curb a person's quality of life.

"Aging is the single greatest risk factor for some of the worst diseases on earth," Ben Kamens, the founder and CEO of a new antiaging startup called Spring Discovery, recently told Business Insider.

Indeed, as we get older, the risk of many diseases — including cancer, heart disease, and Alzheimer's — skyrockets. But without an agreed-upon definition of aging, the path forward for therapies, drugs, or other interventions that aim to treat it remains somewhat obscure, according to the authors of a recent paper summarizing the outcomes of an international meeting on antiaging therapies convened by the National Institutes of Health.

That means one of the "ultimate goals" of studies that test antiaging treatments is "FDA approval for an aging-related indication," the authors concluded.

The FDA is working on criteria for such an indication, according to executives at several longevity companies who spoke with Business Insider anonymously because the agency has yet to make the list of criteria public.

Part of that work, the executives said, includes creating a list of the hallmark components of aging. It includes elements like frailty, muscle loss, and reduced cognitive function, they said. (An FDA representative declined to discuss details of the agency's work on the matter because those plans were not public.)

In the meantime, longevity is a hot and growing area for nascent companies. And people at those companies say now is the best time to be in the field. Here's why.

Longevity is more than skin deep

Scientists at the longevity company Alkahest study blood plasma to create drugs that fight age-related disease. Getty Images/Joern Pollex

Dozens of new companies have flocked to the antiaging field in recent years. As of last fall, investors had bet $850 million on antiaging and longevity startups in 2018, nearly triple the amount they contributed to the field the entire year prior, according to an October report from the CB Insights. Before 2016, the longevity field was almost nonexistent, the report's authors concluded.

But in the absence of a formal definition of senescence, insiders at these longevity companies must decide whether to place their bets on one of several aspects of aging. Most seem to either focus on aging's visible components, such as hair loss and skin elasticity, or narrow in on conditions that manifest beneath the surface, such as diseases like Alzheimer's, cancer, and arthritis.

Those who are betting on the less visible are concentrating their efforts on speeding up the process of creating better drugs for age-related diseases.

A longevity company called Alkahest, for example, screens blood plasma for proteins that could eventually be used to create targeted drugs for a type of eye disease that crops up in old age.

Elizabeth Jeffords, Alkahest's chief commercial and strategy officer, told Business Insider that while the company initially considered focusing on the more visible symptoms of aging, it ultimately decided to home in on age-related disease.

"We did this soul-searching," Jeffords said, eventually strategically deciding to focus the team's effort "to where it could do the most good, and that's in these critical disease-related aging areas."

Relatedly, the researchers at Spring Discovery and Insilico Medicine are trying to hasten the drug-discovery process using advanced data-analysis tools.

Read more: The man who helped build Silicon Valley's premier education startup is diving into the antiaging fight with a fresh $18 million

Other startups aim to allow people to preserve their own personal fountains of youth. Forever Labs, for example, lets customers bank their stem cells, which naturally regenerate and can develop into many different cell types, including muscle and brain cells.

Yet these startups all lack a clearly defined illness that their therapies would treat. They face another obstacle, too: designing the kinds of studies that would enable them to assess whether their treatments work.

The fight to 'unlock a whole new set of tools'

A startup called Forever Labs lets people bank their own stem cells. Getty Images/Spencer Platt

Designing studies to test whether antiaging treatments are effective "poses a unique set of challenges," the National Institutes of Health researchers concluded in their paper.

The aging population is highly diverse, for example. Also, most people will develop several conditions and diseases as they age.

But within the past year, researchers at several leading health organizations including the World Health Organization, the European Medicines Agency, and the FDA have all taken strides to improve these efforts.

The World Health Organization, for example, recently added "aging-related" to its international list of diseases. Last year, the European Medicines Agency published a paper that seeks to come up with an official definition for frailty, which is currently regarded simply as weakness or infirmity, for use in clinical trials.

Robert Temple, the FDA's deputy center director for clinical science, told Business Insider that while he could not confirm which aspects of aging the agency would ultimately use to assess potential treatments, regulators were thinking about both age-related diseases and other age-related effects, like the loss of skin elasticity or the fading of muscle tone.

Official definitions notwithstanding, the folks behind antiaging companies say now is the most exciting time to be in the field.

And when endpoints for aging do eventually service, they'll "help unlock a whole new set of tools," Spring Discovery's Kamens said.

"It's going to happen at some point."