In 1938, researchers at Harvard began tracking 724 men from radically different backgrounds: one group from Harvard's undergraduate classes, the other from Boston's poorest neighborhoods. They gathered health records, conducted in-person interviews every few years, asked detailed questions about their lives, and eventually expanded the study to include spouses and over 1,300 descendants of the original participants.
The Harvard Study of Adult Development is now 87 years old, making it the longest scientific study of happiness and health ever conducted. And after analyzing vast medical records, hundreds of interviews, brain scans, and questionnaires spanning nearly nine decades, the researchers arrived at a conclusion that surprised almost everyone.
Robert Waldinger, the study's current director, put it simply: "Close relationships, more than money or fame, are what keep people happy throughout their lives."
But the finding went deeper than that. When researchers gathered everything they knew about participants at age 50, it wasn't their cholesterol levels that predicted how they would age. It wasn't their exercise habits or their diet. "It was how satisfied they were in their relationships," Waldinger explained. "The people who were the most satisfied in their relationships at age 50 were the healthiest at age 80."
Those strong relationships protected participants' brains, too. People in secure, supportive relationships in their 80s maintained sharper memories than those in high-conflict relationships or social isolation, even when they experienced the same level of physical pain. "Good relationships don't just protect our bodies," Waldinger noted in his TED talk, which has been viewed 44 million times. "They protect our brains."
Social Connection vs. Everything Else
The Harvard study isn't an outlier. A growing body of research reveals that social connections aren't just nice to have—they're as crucial to longevity as the health behaviors we've spent decades quantifying and optimizing.
A meta-analysis examining studies that averaged seven years found that people with larger social networks were about 45% less likely to die during the study period. The effect size was striking enough that researcher Marta Zaraska, in her book Growing Young: How Friendship, Optimism, and Kindness Can Help You Live to 100, argues we've been overlooking a critical part of wellness by focusing only on diet and exercise.
The comparison to other health risks is stark. Research published in the Proceedings of the National Academy of Sciences found that the magnitude of social isolation's effect on mortality is "comparable to that of smoking and exceeds those of many other known risk factors of mortality, such as obesity or physical inactivity."
Another comprehensive review covering more than 300,000 participants found that having strong social support increases survival by 50%—a benefit as powerful as quitting a 15-cigarette-a-day smoking habit.
University of North Carolina researchers examined how social relationships affect concrete physical health markers like inflammation, blood pressure, and abdominal obesity. They found that in adolescence, social isolation increased the risk of inflammation by the same amount as physical inactivity. Throughout adulthood, social integration protected against these biomarkers that lead to chronic disease.
The cardiovascular effects are particularly dramatic: loneliness and social isolation are associated with a 29% increased risk of heart disease and a 32% increased risk of stroke. Socially isolated people were more than twice as likely to develop hypertension—a risk greater than that of diabetes.
The biological mechanisms are well-documented. Loneliness triggers chronic stress responses, increasing cortisol and inflammation while weakening immune function. In one study, participants who were socially isolated were 45% more likely to become ill when deliberately exposed to a cold virus. Meanwhile, positive social connections trigger the release of oxytocin, which lowers cortisol, reduces pain, and even promotes the growth of new brain cells.
The Fitness Industry: A Case Study in Quantification
So if social connection rivals or exceeds exercise and diet in determining how long and how well we live, why can you track every calorie burned but have no idea whether your friendships are healthy?
The answer lies partly in the history of the wellness industry itself—and what could be profitably measured and sold.
The modern wellness movement traces back to the late 1950s, when Dr. Halbert L. Dunn, often called the father of the movement, defined "high-level wellness" as "a condition of change in which the individual moves forward, climbing toward a higher potential of functioning." Dunn's framework was explicitly individualistic—wellness was about your unique journey toward optimization, not about community health or social bonds.
The fitness tracking boom took this individualism and made it quantifiable. When Fitbit launched its first device in 2009, tracking steps, distance, and estimated calories burned, it tapped into decades of fitness-focused culture. The Japanese walking craze of the 1960s introduced the 10,000-step ethos. The jogging boom of the 1970s made pedometers surge in popularity. Dieters had long tracked calories through programs like Weight Watchers, founded in 1963.
By the time Fitbit went public in 2015, the company was valued at $4 billion, reaching $9.7 billion by year-end. The broader fitness tracker market has exploded since then—industry revenue hit $41.94 billion in 2021 and is projected to reach $114.36 billion by 2028.
The success of fitness tracking wasn't accidental. It offered something profoundly appealing: clear, objective numbers that told you whether you were winning or losing at health. Steps, calories, heart rate, sleep cycles—all quantified, all optimizable, all focused on what you as an individual could control.
Why Social Health Got Left Behind
Social connections resisted this quantification for several interconnected reasons, each rooted in how capitalism and individualism shaped wellness culture.
First, the problem of measurability. Steps and calories are discrete, objective units. How do you quantify the depth of a friendship? The quality of emotional support? The strength of community ties? These are inherently relational and contextual—far messier than data points from an accelerometer.
Second, the individualism problem. The modern wellness industry is built on what researchers call "robust individualism"—the idea that health is a personal responsibility achieved through self-discipline and the right purchases. Yoga, meditation, and herbal medicine were stripped from their communal cultural contexts and repackaged as premium products for individual consumption.
As wellness researcher Sirin Kale notes, wellness culture has consistently been structured around "three tenets: robust individualism, distrust of Western medicine and a commitment to self-optimisation." Relationships don't fit this framework. You can't optimize a friendship alone. Community connection by definition requires looking beyond yourself.
Third, the capitalism problem. Researchers Tamara K. Nopper and Eve Zelickson coined the term "wellness capitalism" to describe how employee health became a profitable industry focused on monitoring individual behaviors rather than addressing systemic factors affecting wellbeing.
The wellness industry, valued at $4.9 trillion globally in 2019 and projected to reach nearly $7 trillion by 2025, profits from selling you solutions to problems—both real and imagined. Strong social connections, by contrast, don't require subscriptions or premium upgrades. They require time, vulnerability, and investment in other people—activities that don't generate quarterly earnings reports.
As one wellness critic puts it, the industry "conveniently reduces systematic problems to the individual and frames stress as a personal problem rather than a systematic feature of the workplace." Your gym can sell you solutions for being out of shape. What would it sell you for being lonely?
The Cost of Not Measuring
The absence of social health metrics isn't just an interesting oversight—it has real consequences for how we live and what we prioritize.
Harvard study director Robert Waldinger notes that in 2018, the average American spent 11 hours every day on solitary activities like watching television and listening to the radio. During a 29-year period, that translates to 4,851 days interacting with media—compared to just 58 days spent with a friend.
Before the COVID-19 pandemic, about one in three people globally reported being chronically lonely. The pandemic increased these numbers, but it didn't create the crisis—it merely exposed how fragile our social infrastructure had become.
The U.S. Surgeon General issued a national advisory in May 2023 calling loneliness and social isolation an "epidemic" and a public health concern on par with smoking and obesity. Yet while we have detailed frameworks for measuring and improving physical fitness, social health remains unmeasured, untracked, and largely unaddressed.
We manage what we measure. Without metrics for social health, we default to optimizing what is measured—steps, calories, sleep cycles—while our relationships atrophy from neglect.
What Measurement Changes
The fitness tracking revolution demonstrated something crucial: measurement changes behavior.
Studies using Fitbit activity data revealed that users got significantly more daily physical activity than non-wearable users. The act of tracking created awareness, which created accountability, which changed behavior. Community features like step challenges and leaderboards transformed fitness from a solitary pursuit into a social motivator.
University of North Carolina researcher Kathleen Mullan Harris summarized the implication: "Based on these findings, it should be as important to encourage adolescents and young adults to build broad social relationships and social skills for interacting with others as it is to eat healthy and be physically active."
But how do you encourage something you don't measure? How do you know if you're succeeding at building social health when there's no equivalent to your step count or heart rate variability?
The Harvard study researchers created a tool to help people take inventory of their relationships—mapping who provides different types of support (emotional, practical, fun, security) and identifying gaps. Simply making social connection visible changed how people thought about and invested in their relationships.
A 2023 proposal in the journal Lifestyle Medicine called for national health guidelines for social connection, similar to existing guidelines for diet, exercise, and sleep. The researchers argued that despite the complexity of measuring social connection, "we should not let the complexity hold us back from acting."
Why Now Is the Time
We're finally reaching a point where the tools and understanding exist to quantify social health in meaningful ways.
Research has identified specific dimensions of relationship health: emotional intimacy, trust and security, quality of communication, support exchange, and conflict management. These aren't vague concepts—they're measurable through patterns in how people interact, communicate, and show up for each other.
The data infrastructure exists. We track our steps, our sleep, our screen time. We have calendars full of meetings and contacts full of names. What's missing isn't the ability to measure social health—it's the framework and tools that make that measurement useful and actionable.
Longevity expert Dr. Peter Attia emphasizes that social relationships, emotional health, and sense of purpose are underappreciated "levers" for extending both lifespan and healthspan—the period of life spent in good health. Blue Zones research, examining regions where people live significantly longer than average, consistently identifies robust social networks as a key feature.
The question isn't whether social health can be measured. It's whether we're willing to treat it with the same seriousness we've brought to physical fitness.
What You Can Do Right Now
While comprehensive social health tracking tools are still emerging, you don't need to wait for a "Fitbit for friendships" to start treating your relationships as seriously as your workout routine.
Map your social network. Take an honest inventory of your relationships. Who do you spend time with? Who provides emotional support? Who makes you feel energized versus drained? Where are the gaps? You can't improve what you don't see clearly.
Schedule social time like you schedule workouts. In Okinawa, Japan—one of the world's Blue Zones—elders participate in "moais," small groups of lifelong friends who meet regularly for support and companionship. You don't need a formal structure, but you do need intentionality. Put friend time on your calendar with the same priority as gym time.
Track quality, not just quantity. It's not about how many friends you have or how many social interactions you log. The Harvard study showed that relationship quality at age 50 predicted health at 80—not the size of your social network. One close friend you can truly count on matters more than a dozen superficial connections.
Practice "social fitness" actively. Harvard researchers note that we tend to think once we establish friendships, they'll take care of themselves. They won't. Like physical fitness, social fitness requires ongoing effort and attention.
Recognize that screens aren't connection. The Harvard study reminds us that being social online is not the same as being connected in real life. Phone calls beat text messages. In-person conversations beat phone calls. The depth of connection matters more than the convenience of the medium.
Start treating loneliness like a health risk. If you felt the physical symptoms of high blood pressure, you'd address it. Social isolation carries similar health risks, but we've been conditioned to see it as a personal failure rather than a medical concern. It's neither—it's a measurable health metric that can be improved with intentional action.
The Path Forward
Eighty-seven years of Harvard research, hundreds of supporting studies, and mounting public health data all point to the same conclusion: your relationships matter more for your longevity than your exercise routine, your diet, or your genes.
Yet we live in a world where you can get a detailed breakdown of your sleep stages from last night but have no clear picture of whether your most important relationships are thriving or merely surviving. Where your phone will remind you to stand up and move, but never to call a friend you haven't talked to in months.
The fitness revolution taught us that measurement drives behavior change. Millions of people transformed their health by making the invisible visible—by turning abstract goals into concrete numbers they could track, improve, and celebrate.
It's time to apply that same principle to the health metric that matters most. Not because social connection should become another thing to optimize and stress about, but because when we measure what truly matters, we stop neglecting it in favor of what's merely easy to count.
Your gym will always have metrics for your workout. The question is: when will your social life get the same attention?