Social Isolation Rivals Hypertension as Mortality Risk Factor

Megan Brooks

September 17, 2013

Social isolation is a risk factor for premature death that rivals more traditional mortality risk factors of smoking and high blood pressure, a study shows.

Investigators at the University of California Berkeley–University of San Francisco Joint Medical Program in San Francisco found that social isolation predicted mortality for both sexes, as did smoking and high blood pressure.

The "power of isolation as a marker of poor health cannot be ignored," lead investigator Matthew Pantell, MD, and colleagues write.

The study was published online September 12 in the American Journal of Public Health.

More Social Isolation, Increased Mortality

According to investigators, although clinicians routinely monitor biological risk factors, they rarely assess patients' social isolation or engagement.

"Understanding the relative predictive value of social isolation with respect to mortality would contribute to a fuller understanding of potentially modifiable risk factors," the authors write.

For the study, the researchers analyzed data on 16,849 adults participating in the Third National Health and Nutrition Examination Survey (NHANES III) and the National Death Index.

The researchers used the Social Network Index (SNI) to measure social isolation. Participants received a score of 0 or 1 for each SNI domain (marital status, frequency of contact with other people, participation in religious activities, and participation in other club or organization activities). Scores ranged from 0 to 4, with 0 representing the highest level of social isolation and 4 representing the lowest level.

The researchers found that low SNI scores (indicating greater social isolation) were predictive of mortality among men (hazard ratio [HR], 1.62; 95% confidence interval [CI], 1.29 - 2.02) and were associated with a risk for mortality similar to that of smoking (HR, 1.72; 95% CI, 1.48 - 2.00) and higher than that of high blood pressure (HR = 1.16; 95% CI, 1.02 - 1.32).

Similarly, social isolation was also an important predictor of mortality among women (HR, 1.75; 95% CI, 1.38 - 2.23), as were smoking (HR, 1.86; 95% CI, 1.64 - 2.12) and high blood pressure (HR, 1.32; 95% CI, 1.17 - 1.48).

"Gradients in risk were observed for women and men, with increasing isolation associated with a greater risk of mortality," the researchers write.

Modifiable Risk Factor

Given overlapping hazard ratios, social isolation factors are "not necessarily better" predictors than traditional factors, but they are "at least equally important. Sensitivity analyses confirmed the strength of the predictive value of social isolation for both men and women," they note.

In models incorporating all of the clinical and individual social variables assessed, unmarried status and infrequent religious activity predicted mortality among both men and women. In addition, lack of group memberships predicted mortality among men, and infrequent social contact predicted mortality among women.

"Our results emphasize the value of identifying social isolation as a potentially modifiable risk factor" for premature death, the researchers write.

In reality, however, a patient’s social history is often "inadequately" explored in healthcare encounters. The researchers believe 4 brief questions included in the modified SNI scale, or a similar set of questions, could help clinicians identify individuals at higher risk for mortality.

"In a busy clinical setting, adding these items to standardized screening questions administered electronically or by nonmedical clinic staff and highlighting patients' responses for the physician when a threshold is reached would not add substantially to clinician burden, and it could potentially help in discerning which patients have worse health outcomes and targeting those patients for increased surveillance," the authors conclude.

The authors have disclosed no relevant financial relationships.

Am J Public Health. Published online September 12, 2013. Abstract


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