Social Isolation Directly Affects Health, Ups Risk of Death

Pam Harrison

November 20, 2018

Social isolation is a robust predictor of all-cause and cardiovascular disease (CVD) mortality in both blacks and whites, and it also predicts cancer-related death among whites, a nationwide cohort of individuals living in the United States indicates.

The study was published online October 16 in the American Journal of Epidemiology. 

"Social isolation is our most well-established social risk factor for poor health and premature death — in fact, it's been called the 'new smoking' in terms of its potential impact on the future of public health," Kassandra Alcaraz, PhD, MPH, American Cancer Society, Atlanta, Georgia, told Medscape Medical News in an email.

Social isolation directly affects health by causing changes in the body such as inflammation.    Kassandra Alcaraz, PhD, MPH

"Based on existing scientific evidence, we believe social isolation directly affects health by causing changes in the body such as inflammation, cognitive decline, hypertension, and poor immune functioning," she said.

"We also think that social isolation indirectly affects health via various mechanisms, such as behavior — people who are isolated may be more likely to smoke or have sleep disturbances — or have psychological implications — isolated people may be more stressed or depressed than others — and it might also affect healthcare utilization because isolated individuals might not have people reminding them to take care of their health," she added.

"In all, we believe both direct and indirect effects of social isolation lead to poorer health outcomes and, ultimately, premature death," Alcaraz emphasized.

Asked what effect social media might have on population health now and in the future, Alcaraz predicted that the long-term adverse consequences on population health may well be "huge" because virtual "connections" are probably no replacement for real-world interactions.

"Younger people might face a greater risk for social isolation and poor health than adults today because if youth are not forming meaningful personal relationships due to over-reliance on technological connections, they might lack the skills to be connected to others in real life as they age," she suggested.

Physicians and other healthcare providers are not really in a position to intervene and help socially isolated patients, Alcaraz acknowledged.

However, "merely recognizing that social isolation can impact health would be a first step both for physicians and people in general, and perhaps patients identified as socially isolated could be referred by physicians for supportive services," as she suggested.

Study Details

The analysis was carried out on 580,182 individuals who took part in the American Cancer Society's Cancer Prevention Study II (CPS-II), in which participants were enrolled in 1982 and followed to 2012.

"The CPS-II baseline questionnaire queried participants on marital status, frequency of church/temple attendance, and club meetings/group activities, and number of close friends/relatives," the authors observe.

Each component of the Social Network Index was weighted equally with a score of 0 signifying the least isolated or 1 for the most isolated. The social isolation score was the sum of its four components and ranged from 0 to 4 for the least to the most isolated.

The authors note that they only assessed participants for their level of social isolation at baseline, and point out that this may well have changed over the 30-year follow-up.

In the study, they first compared the association between social isolation scores and risk of all-cause mortality during the first 15 years of follow-up (1982-1997) and second 15 years of follow-up (1998-2012).

This analysis revealed that the association between social isolation and all-cause mortality was stronger during the first 15 years of follow-up and they thus limited all other analyses to the earlier interlude.

"Overall, race seems a stronger predictor of social isolation score than sex as both white men and women were more likely to be in the least isolated category than black men and women," Alcaraz and colleagues observe.

In both races and in both sexes, investigators documented statistically significant associations between social isolation scores and all-cause mortality.

Specifically, among white women, the risk of all-cause mortality was 84% higher among the most isolated women compared with the least isolated women, investigators note.

This risk was actually higher than it was for white men, where the most isolated men had a 60% higher all-cause mortality risk than the least isolated men (P = .01).

In contrast, among blacks there was no gender difference in the risk of all-cause mortality between the most versus the least isolated, the authors observe.

"Social isolation score was [also] positively associated with CVD mortality in all subgroups," the authors continue, although the association was again stronger among white women than white men (P < .0001).

There was also a positive association between cancer mortality and social isolation scores among white men and women (P < .0001). The risk of death was approximately 25% higher for both sexes for the most versus the least socially isolated men and women.

In contradistinction, no association between social isolation scores and cancer mortality was observed among black men or women, the study authors note.     

Social Isolation Components

Investigators also observed that each component in the social isolation score — being married or not, number of close friends and relatives, club or group participation, and religious service attendance — were all significantly associated with both all-cause and CVD mortality risk.

For example, being unmarried was associated with a 17% higher risk of all-cause mortality and a 25% higher risk of CVD mortality in the overall cohort.

This risk did not differ by race, although being unmarried was more strongly linked to mortality risk among men than among women of both races (P < .01).

Interestingly, the other components of social isolation were also significantly linked to a higher risk of all-cause mortality among white men but not black men, as researchers point out.

Among white women, all components of the social isolation score were associated with a higher all-cause mortality risk, but for black women the number of close friends and relatives was not linked to a higher all-cause mortality risk.

That said, black women who rarely or never attended religious services had a 32% higher mortality risk compared with only 11% of their white counterparts, suggesting the weight of each of the social isolation components differed by race and sex.

The authors have reported no relevant financial relationships.

Am J Epidem. Published online October 16, 2018. Abstract

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