A recent study published in Biological Psychology provides new insights into the link between loneliness and cardiovascular health. The research found that loneliness is associated with reduced heart rate variability during acute social stress, which suggests a decreased ability of the autonomic nervous system to regulate cardiovascular function. This effect was more pronounced in women than in men.
Loneliness is a deeply personal experience defined by a gap between the social connections an individual desires and what they actually have. It is not simply about being alone; rather, it reflects the subjective distress of feeling disconnected or unsupported by meaningful relationships. This sense of isolation, whether physical or emotional, has significant implications for mental and physical health.
Beyond feelings of unhappiness, loneliness is linked to a higher risk of chronic illnesses, particularly cardiovascular diseases such as heart attacks and strokes. Despite its importance, the physiological mechanisms that connect loneliness to such outcomes remain unclear, prompting researchers to explore the deeper biological underpinnings of this link.
“I have been focusing on the health impacts of loneliness for more than a decade. Over the years, our research team has conducted a series of population studies demonstrating that loneliness is a significant risk factor for various adverse health outcomes. Among these, cardiovascular health has consistently shown the strongest and most robust associations,” said
study author Bin Yu, an associate professor of health psychology at Tianjin University.
“Building on these findings, we turned our attention to the physiological mechanisms underlying the link between loneliness and cardiovascular health. Atypical cardiovascular reactivity to acute stress has been identified as a potential pathway contributing to negative cardiovascular outcomes. Previous studies have explored cardiac measures such as heart rate, blood pressure, and cardiac impedance in response to stress, but heart rate variability has been largely overlooked.”
Heart rate variability—a measure of the time differences between heartbeats—is an important indicator of autonomic function. High variability suggests a healthy, adaptable system, while reduced variability is linked to poor cardiovascular outcomes.
“Heart rate variability reflects autonomic nervous system functioning and its reactivity to stress is believed to play a critical role in cardiovascular health,” Yu explained. “This gap motivated us to conduct this study, focusing on cardiovascular reactivity to acute social stress among younger adults.”
The researchers recruited 97 college students aged 17 to 29, ensuring all participants were in good physical health and free from significant recent life events. Before the experiment, participants adhered to guidelines to avoid smoking, alcohol, and caffeine for 24 hours and abstained from eating for one hour. Of these, 92 participants (52 women) provided usable data after exclusions for poor-quality measurements.
To measure loneliness, the team used the revised UCLA Loneliness Scale, which assesses how often individuals feel disconnected from others. Participants also completed assessments of neuroticism, social network size, and mood to control for potential confounding factors.
The researchers induced acute social stress using the Trier Social Stress Test, a well-established protocol. This test involved a five-minute public speaking task followed by a mental arithmetic challenge, performed in front of evaluators who maintained a cold and evaluative demeanor. Heart rate variability and heart rate were monitored throughout the experiment using electrocardiogram equipment. The data were analyzed to compare participants’ physiological responses during baseline, stress, and recovery periods.
The researchers found that loneliness was associated with diminished heart rate variability reactivity during social stress, even after accounting for factors such as age, sex, and neuroticism. This reduced variability indicates that the autonomic nervous system of lonely individuals may be less effective at regulating cardiovascular responses under stress. In simpler terms, their bodies showed less flexibility in adapting to the demands of a stressful situation.
“During stress, cardiac measures such as heart rate and blood pressure typically increase, and earlier research has shown that lonely individuals may exhibit exaggerated or blunted reactivity to social stress,” Yu told PsyPost. “However, the implications of exaggerated or blunted reactivity for cardiovascular health remain debated.”
“In contrast, heart rate variability generally decreases under stress, and blunted cardiovascular reactivity is widely recognized as detrimental to cardiovascular health. Our study is the first to demonstrate that lonely individuals are more likely to exhibit blunted cardiovascular reactivity to acute social stress. These findings provide a potential physiological explanation for the link between loneliness and poorer cardiovascular health outcomes.”
Interestingly, the researchers observed notable differences between men and women. Women who reported higher levels of loneliness exhibited more significant reductions in heart rate variability reactivity, while no such association was found in men. This sex-specific pattern aligns with previous findings suggesting that women may rely more on social connections for stress regulation, making them more vulnerable to the physiological effects of loneliness.
“Overall, the findings were in line with our expectations,” Yu said. “However, we were slightly surprised to observe sex differences in the results. Specifically, the association between loneliness and cardiovascular reactivity was more pronounced among women. This opens a new avenue for understanding how gender might moderate the health effects of loneliness.”
Additionally, the study found that loneliness was linked to reduced heart rate reactivity during stress, further supporting the idea that loneliness affects the autonomic nervous system’s stress response. Importantly, the findings emphasize loneliness as a subjective experience, distinct from objective measures of social isolation such as the size of one’s social network.
As with all research, the study has limitations. Its cross-sectional design means the researchers could not establish a causal relationship between loneliness and reduced cardiovascular reactivity. Longitudinal studies would be needed to determine whether loneliness directly leads to these physiological changes or whether other factors are involved. The relatively small sample size, though adequate for this type of research, limits the generalizability of the results to broader populations.
“Most evidence linking loneliness to cardiovascular health comes from studies on older populations,” Yu noted. “While our findings suggest that the detrimental effects of loneliness may manifest earlier in life than previously thought, it is important to note that our sample consisted of young adults. As such, these results may not generalize to other age groups, particularly older adults. Future research should explore these associations across the lifespan to provide a more comprehensive understanding.”
Additionally, the study’s reliance on a laboratory setting may not fully capture how loneliness affects cardiovascular responses in real-world scenarios. To address this, Yu and his colleagues plan to use wearable technology to monitor heart rate variability in everyday life.
“Advances in wearable technology now enable real-time heart rate variability monitoring, allowing us to conduct ecological momentary studies that capture cardiovascular responses to social stress in naturalistic settings,” Yu said. “Such research promises to provide deeper insights into how loneliness impacts cardiovascular health in everyday life.”
“Although this is only an experimental study that preliminarily reveals the underlying mechanisms linking loneliness and cardiovascular health, accumulated evidence indicates that loneliness and social isolation significantly increase the risk of heart attack, stroke, and even early death,” he added. “As a member of the WHO Advisory Group on Social Connection, I would like to appeal to the public to recognize that reducing loneliness by fostering social connections is far more important for both physical and mental health than previously thought.”
The study, “Loneliness is associated with diminished heart rate variability reactivity to acute social stress in younger adults,” was authored by Yunlong Song, Zhengqi Sun, Fengping Luo, and Bin Yu.
