May 04, 2021
Loneliness among middle-aged men ups their risk of cancer, and being single at the time of diagnosis confers a worse prognosis, suggest results from a longitudinal Finnish study with a mean follow-up of 20 years.
The study also found that although loneliness was associated with an increased risk of cancer, social isolation was not.
It's not clear why loneliness had a stronger association with cancer compared with social isolation, but it could be linked to satisfaction, commented lead author Siiri-Liisi Kraav, MSc, a PhD student at the University of Eastern Finland, Kuopio.
"For many people, their level of social contacts (social isolation) is satisfactory, and it does not necessarily cause suffering. Loneliness, however, by definition includes dissatisfaction with the situation," Kraav told Medscape Medical News.
The mechanisms underlying the association are unclear, but one possibility is inflammation. "It has been proposed that loneliness might disturb hypothalamic–pituitary–adrenal axis (HPA axis) functions and increase low-grade inflammation either directly, via unhealthy lifestyle or depression," she explained.
The findings are a call to action, Kraav suggested. "Loneliness has a lot of adverse health effects; increased cancer incidence is only one of them. So, it would be important to prevent these negative effects by developing effective interventions for loneliness and to routinely screen for loneliness."
The study was published in the May issue of Psychiatry Research.
"There is a large literature linking both social isolation and loneliness to all-cause mortality and cardiovascular outcomes, but less specific to cancer," commented Julianne Holt-Lunstad, PhD, who was not involved in the study.
"Further, many studies just look at isolation or loneliness, but fewer studies include them both among the same sample," she said. "So, this helps us better understand how the experience of social isolation and loneliness influence both the incidence and mortality rates associated with cancer."
Holt-Lunstad, a professor of psychology and neuroscience at Brigham Young University in Provo in Utah, has published extensively on the health impact of loneliness, and more recently, about loneliness and COVID-19 (World Psychiatry. 2021;20:55-56).
The health impact of loneliness and social isolation triggered by the pandemic may not be fully understood for "years or decades to come," Holt-Lunstad told Medscape Medical News. "While I hope the majority of people will be resilient or recover, I suspect at least a subset of the population will have chronic effects. Thus, we need to continue to study this issue and prioritize addressing it in public health."
The Finnish study involved 2570 men, aged 42-61 years, who participated in the Kuopio Ischaemic Heart Disease Risk Factor (KIHD) study.
Baseline variables relating to lifestyle, socioeconomic status, depression, and physical health were assessed along with loneliness and social isolation.
An 11-item Loneliness Scale was used to measure subjective satisfaction with one's social life, feelings of loneliness, and the perceived discrepancy between desired and actual social contacts. Social isolation was measured using a different 10-item scale measuring "the amount and frequency of different social contacts a person has," explained Kraav.
During a mean follow-up of 20.4 years, 649 men (25.3%) developed cancer (hazard ratio [HR], 1.10; P = .028), and 283 died of the disease. Mean age at cancer diagnosis was 70 years, and the most common cancers were prostate (n = 236, 9.2%), lung (n = 87, 3.4%), and colorectal (n = 79, 3.1%).
Participants who were diagnosed with cancer "were older than their healthy counterparts, drank more alcohol, and were more often smokers," noted the authors.
However, multivariate analysis showed that loneliness was associated with total cancer incidence even after adjusting for a long list of covariates, including age, socioeconomic status, alcohol consumption, smoking, physical activity, diet, sleep, depression, high-sensitivity C-reactive protein, systolic blood pressure, cholesterol, body mass index, and cardiovascular disease history.
The association of social isolation with cancer incidence was lost after adjusting for lifestyle variables.
The study also found that among the men who were diagnosed with cancer, those who were single, divorced, or widowed at baseline died earlier than those who were married or living with a partner, at an average of 21.5 vs 23.4 years from baseline (P = .003).
However, the authors acknowledged a study limitation was that loneliness, social isolation, and relationship status were only measured once, at baseline. "It is possible that for some of the participants, numerous changes occurred in their living arrangements and relationships during the follow-up period, and having information about these changes would have enhanced the discussion of possible explanatory mechanisms," state the authors.
Siiri-Liisi Kraav was supported by the Finnish National Agency for Education's scholarship. Kraav and Holt-Lunstad have both reported no conflicts of interest.
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