Written by Shereen Hussein & Jonathan Samet, Editors-in-Chief of Population Health Metrics

As the world marks World Population Day 2025, we are called not only to reflect on population dynamics and demographic shifts, but also to reconsider the often overlooked drivers of health and wellbeing that affect all communities, globally. This year’s celebration aligns with a powerful new global initiative: the WHO Commission on Social Connection has released a groundbreaking report, From Loneliness to Social Connection – Charting a Path to Healthier Societies. The report positions social connection as a fundamental component of population health, on par with physical and mental health, and no less urgent.

Social connection, as the report defines it, encompasses the structural, functional, and quality dimensions of our relationships with others. It is not merely about how many people we interact with, but how those interactions meet our needs for support, belonging, and trust. Yet, despite being an intrinsic part of human wellbeing, social connection has long been overlooked in population health research and public policy. Former US Surgeon General Vivek Murthy, co-chair of the WHO Commission, called attention to loneliness in his 2023 report: Our Epidemic of Loneliness and Isolation. The U.S. Surgeon General’s Advisory on the Healing Effects of Social Connection and Community.  Generally, however, the issue is ignored and under-researched, an omission with real consequences.

The WHO report paints a sobering picture. Between 2014 and 2023, an estimated one in six people globally experienced loneliness, with the highest rates observed among adolescents and young adults; 20.9% of 13–17-year-olds and 17.4% of 18–29-year-olds. Older adults are not exempt: about one in three are socially isolated, meaning they lack sufficient social contact and roles. The burden is especially acute in low-income countries, where nearly one in four people report feeling lonely. Beyond age and geography, marginalised populations, people with disabilities, migrants, LGBTIQ+ individuals, face a disproportionate risk of social disconnection.

The consequences of this growing crisis are profound. Social disconnection is not just emotionally distressing; it is deadly. The report estimates that loneliness contributes to 871,000 deaths globally each year, with links to cardiovascular disease, type 2 diabetes, depression, cognitive decline, and early mortality. These effects are not just comparable to, but in some cases exceed, the health risks posed by smoking and obesity. Economically, the cost of loneliness and social isolation, through reduced productivity, increased healthcare use, and diminished educational outcomes, is only beginning to be understood, but is clearly substantial.

And yet, despite this impact, we lack the tools and systems to adequately measure or respond to social disconnection. This is particularly true in low- and middle-income countries (LMICs), where existing metrics may not capture culturally specific expressions of loneliness or forms of social engagement. In many parts of the world, there isn’t even a word that distinguishes between "loneliness" and "solitude", making measurement and intervention complex but all the more necessary. The WHO report identifies this lack of standard, cross-cultural, and life-course-sensitive measurement tools as a major gap in current research—a gap that must be filled if we are to respond effectively.

As Co-Editors-in-Chief of Population Health Metrics, we see this as a moment of opportunity. Our journal is committed to advancing the science of population health through robust, innovative, and inclusive research. In light of the WHO's call to action, we particularly encourage the submission of manuscripts that explore the role of social connection in shaping population-level health outcomes. This includes large-scale epidemiological studies that capture the structural and functional dimensions of social ties, as well as investigations into how connection intersects with mental health, chronic disease, aging, and mortality.

Equally vital are efforts to develop and validate better tools for measuring social connection across diverse cultural and demographic contexts. We know that what constitutes a meaningful connection varies with age, gender, geography, and cultural norms. Adolescents may define connection through digital interactions, while older adults may rely on community networks or intergenerational households. Research that recognizes and captures this diversity will be key to designing equitable interventions.

There is also an urgent need to evaluate interventions and policies aimed at fostering social health, from national loneliness strategies to community-based programmes and digital technologies. The WHO report showcases promising examples from several high-income countries, but there is still little evidence about what works in different settings, especially in LMICs, where community structures and informal networks may play a more central role. As researchers, we must ask: what are the most effective, scalable, and sustainable ways to rebuild connection in a fragmented world?

Ultimately, the case for social connection is not just scientific, it is ethical. In a world grappling with aging populations, mental health challenges, and widening inequalities, fostering social connection is both a moral imperative and a public health necessity. The WHO report reminds us that human beings are inherently relational; our health and survival depend not only on medicine or infrastructure, but on each other. To quote the report’s foreword: “Connection is not just a nice idea. It is fundamental.”

This World Population Day, let us commit to expanding our understanding of health to fully cover social connections and health. Let us build evidence, develop measurement tools, and evaluate interventions that reflect the real, lived experience of connection, or the lack of it. Let us recognize social health as a core concern of population health.

Population Health Metrics stands ready to support this mission by publishing and disseminating research that can inform policy, empower communities, and improve lives. We invite our community, epidemiologists, public health practitioners, sociologists, demographers, and more, to join us in this critical endeavour.

For more on the WHO Commission on Social Connection and to read the full report,

visit: https://www.who.int/groups/commission-on-social-connection

To submit your manuscript to Population Health Metrics,  click here.

 Read these  relevant articles:

1. Living arrangements and lonely life expectancy: a multistate life table based on Markov chains

2. How impact factors, including the COVID-19 pandemic, change the quality of life of the elderly 

3. Regional variations in Italy’s COVID-19 death toll: a descriptive analysis of excess mortality and associated factors from 2020 to 2021