The Rosetto Effect

In the 1950’s, physicians in the small Italian immigrant town of Roseto, Pennsylvania made a remarkable observation: residents of Roseto were dying of heart attacks at much lower rates than those in nearby Bangor. In fact, the risk of dying from a heart attack in Roseto was nearly 50% lower.

Was it their diet? No. They cooked with pig lard, ate pasta and sausages, and drank wine. Researchers could not identify significant differences in their diet, rates of obesity or smoking compared to neighboring towns.

Was it genetics? No. Researchers found that Roseto residents that had moved to other towns suffered the same rates of heart disease as other Americans.

Was it access to health care? No. People in Roseto went to the same doctors and hospitals as those in Bangor.

What set this Italian community apart was their tight-knit social structure:

• Multigenerational households

• High levels of respect for elders

• Strong religious and community ties

• Egalitarian social values with little emphasis on status or materialism

• Low crime

Let that sink in for a moment. Social connection lead to a lower mortality rate from heart disease. This finding became a phenomenon referred to as the "Roseto effect," by which a close-knit community experiences a reduced rate of heart disease and extended life span.

But Roseto isn’t the only place this has been observed.

In 2010, Julian Holt-Lunstad and colleagues published a meta-analysis of 148 studies including 300,000 people. They looked at a variety of measures of social relationships, including marriage status, living alone, size of social network, perception of social support, and perception of loneliness. Their results were incredible: they reported a 50% increased likelihood of survival for participants with stronger social relationships. Look at the figure below from their paper:

Comparison of odds (lnOR) of decreased mortality across several conditions associated with mortality

As you can see, in their analysis social relationships had a stronger association with mortality than smoking, alcohol consumption, physical activity, and obesity.

In 2023, Ryo Nato and colleagues published a meta-analysis of 36 studies that included 1.3 million people. The table below summarizes the hazard ratios of social isolation for all-cause mortality (death from any cause, which is the ultimate outcome in medicine):

As you can see, every single study showed a trend of social isolation increasing the risk of mortality with the majority of the studies being statistically significant. The weighted average (diamond at the bottom) was 1.33. This means a 33% higher mortality was associated with social isolation.

How could social connection lead to better health?

The mechanisms are both behavioral and biological:

• Health behaviors: Socially isolated individuals are more likely to smoke, drink heavily, be physically inactive, and eat poorly (one reference here). In contrast, people with strong social support are more likely to engage in healthy behaviors—such as regular exercise, better diet, and avoiding harmful substances (one reference here).

• Biological: Social isolation increases chronic stress, which elevates cortisol and activates the sympathetic nervous system. Over time, this contributes to hypertension, visceral fat, and insulin resistance. The Jackson Heart Study showed that African Americans with strong social support had a significantly lower incidence of hypertension.

Keep in mind, these are not randomized clinical trials. Both the residents of Roseto and the people in these meta-analyses were not randomly assigned to live in social isolation vs in close-knit communities with all else being equal. Like the data on smoking or VO2 max and their association with health, these data can only tell us correlations, not causation. But the consistency and strength of the associations are hard to ignore.

What does this mean for us?

I would argue that if we want to optimize physical health (let alone mental and emotional health), we need to prioritize social connection. Physical health is not only about sleep, nutrition, and exercise. It’s about prioritizing relationships and investing in community. For me, this means a weekly phone call with a good friend, Wednesday potlucks with families nearby, and riding with a mountain biking group every month. There are so many ways to have social connections and it starts with making it a priority.

Let me end with a story about my 80 yr old mom, who’s tough as nails. She called me this week laying in bed in agonizing leg pain, unable to move, alone, and with the front door locked. Unfortunately, I was an hour away. By the time I arrived, a neighbor’s child had climbed through the bathroom window and unlocked the door. Two different neighbors and her brother were at her bedside having given her pain medication and emotional support. We took her to the hospital and discovered she had a hip fracture. Now she has a new hip and will begin the long journey of rehabilitation. This journey will be made easier by her community: her sister is moving in with her for the next few weeks, her neighbor will walk with her every day, and friends and family will provide food and emotional support. We will do all do our best to make sure she gets back on her feet again—literally. This is the power of social connection.