By Kassandra I Alcaraz, et al, American Journal of Epidemiology

Social isolation—a measure of an individual’s (limited) social contact and networks—is detrimental to health and well-being (1–4). Berkman and Syme (5) developed the Social Network Index, a summary measure of social isolation derived from several components: marital status, participation in church groups and other groups, and number and frequency of contact with close friends/relatives. In age-adjusted analyses, they found that men and women who were the most isolated had 2.3-fold and 2.8-fold higher risks of premature mortality, respectively, than the least isolated (5). Dozens of subsequent studies using various social isolation measures have examined associations with overall mortality, with weighted mean effect sizes between 1.29 and 1.83 (4).

The prevalence of social isolation differs across population subgroups (3, 6), yet evidence on its association with mortality across subgroups is limited. Research has found black-white differences in the health-protective associations of religious involvement (with protective associations being stronger among blacks) (7–9) and number of social contacts (with protective associations being stronger among whites) (9). However, the extent to which these racial differences persist using a measure of social isolation (i.e., one that considers both religious participation and interpersonal relationships) is unknown. Additionally, findings from research examining sex differences in the association between social isolation and mortality have been inconsistent. Some studies, comprising mostly white adults, have suggested that the association between social isolation and all-cause mortality may be similar for women and men (10, 11), although other studies have suggested that social isolation is more deleterious for men (1, 12). Many studies examining sex differences have been hindered by limited statistical power (13–16), and the literature lacks robust evidence on the association between social isolation and mortality by race and sex. Liu (6) studied 9,246 older adults and found the association between social isolation and all-cause mortality to be weakest among white men and strongest among black women. Schoenbach et al. (14) examined social isolation and all-cause mortality in 2,059 adults and found an association only among white men; the association became nonsignificant after adjustment for potential confounders.

The American Cancer Society’s Cancer Prevention Study II (CPS-II) cohort provides an opportunity to examine associations between social isolation and mortality in race-sex subgroups (i.e., black women, black men, white women, and white men) because of its large sample size, comprehensive risk factor assessment, and long-term follow-up for mortality. Using CPS-II data, we compared associations of social isolation with all-cause, cardiovascular disease (CVD), and cancer mortality among sex-race subgroups. Such findings can inform unanswered questions about the role of social isolation in mortality in these subgroups and might be useful in identifying and intervening with patients who are vulnerable to premature death.

RESULTS

Social isolation exposure

In our study population, black women were the most likely to be unmarried; black men and black women were the most likely to have few close friends/relatives; white men were the most likely to attend religious services infrequently; and black men and white men were the most likely to participate in clubs/groups infrequently (Table 1). Overall, race seemed to be a stronger predictor of social isolation score than sex, as both white men and white women were more likely to be in the least isolated category than black men and black women. In all race-sex subgroups, the proportion of current smokers increased and the proportion of persons with at least a high school education decreased with increasing social isolation (Table 2).

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Authors: Kassandra I Alcaraz, Katherine S Eddens, Jennifer L Blase, W Ryan Diver, Alpa V Patel, Lauren R Teras, Victoria L Stevens, Eric J Jacobs, Susan M Gapstur

Read more at: American Journal of Epidemiology, Volume 188, Issue 1, January 2019, Pages 102–109, https://doi.org/10.1093/aje/kwy231

Published: 16 October 2018