Alexander C. Tsai, MD, PhD *; Michel Lucas, PhD, RD *; Ayesha Sania, PhD; Daniel Kim, MD, DrPH; Ichiro Kawachi, MD, PhD
Note: All authors had full access to all of the data in the study and agreed with the decision to submit the manuscript for publication.
Acknowledgment: The authors thank their colleagues in the Channing Division of Network Medicine, Department of Medicine, Brigham and Women's Hospital and at Harvard Medical School for their assistance with the HPFS data and for reviewing the analysis protocol, findings, statistical code, and manuscript.
Grant Support: By the NIH (P01CA055075). Dr. Tsai was supported by NIH K23MH096620 and, with Dr. Kawachi, by a seed grant from the Robert Wood Johnson Foundation Health and Society Scholars Program. Dr. Kim was supported by NIH R00HL089459.
Disclosures: Authors have disclosed no conflicts of interest. Forms can be viewed at www.acponline.org/authors/icmje/ConflictOfInterestForms.do?msNum=M13-1291.
Reproducible Research Statement:Study protocol: Available at www.hsph.harvard.edu/hpfs. Statistical code: Available from Dr. Tsai (e-mail, firstname.lastname@example.org). Data set: External collaborator information is available at www.hsph.harvard.edu/hpfs.
Requests for Single Reprints: Alexander C. Tsai, MD, PhD, Center for Global Health, Room 1529-E3, Massachusetts General Hospital, 100 Cambridge Street, 15th Floor, Boston, MA 02114; e-mail, email@example.com.
Current Author Addresses: Dr. Tsai: Center for Global Health, Room 1529-E3, Massachusetts General Hospital, 100 Cambridge Street, 15th Floor, Boston, MA 02114.
Dr. Lucas: Centre de Recherche du Centre Hospitalier Universitaire de Québec, Université Laval, 2875, Boulevard Laurier, Edifice Delta II, Bureau 600, Québec City, Québec G1V 2M2, Canada.
Dr. Sania: Room 911, Building 3, Harvard School of Public Health, 677 Huntington Avenue, Boston, MA 02115.
Dr. Kim: Department of Health Sciences, Bouvé College of Health Sciences at Northeastern University, 360 Huntington Avenue, Robinson Hall Room 316J, Boston, MA 02115.
Dr. Kawachi: Department of Social and Behavioral Sciences, Harvard School of Public Health, 677 Huntington Avenue, Kresge Building, 7th Floor, Boston, MA 02115.
Author Contributions: Conception and design: A.C. Tsai, I. Kawachi.
Analysis and interpretation of the data: A.C. Tsai, M. Lucas, A. Sania, D. Kim, I. Kawachi.
Drafting of the article: A.C. Tsai.
Critical revision of the article for important intellectual content: A.C. Tsai, M. Lucas, A. Sania, D. Kim, I. Kawachi.
Final approval of the article: A.C. Tsai, M. Lucas, A. Sania, D. Kim, I. Kawachi.
Provision of study materials or patients: I. Kawachi.
Statistical expertise: A.C. Tsai, M. Lucas, A. Sania, I. Kawachi.
Obtaining of funding: A.C. Tsai, I. Kawachi.
Administrative, technical, or logistical support: I. Kawachi.
Collection and assembly of data: I. Kawachi.
Suicide is a major public health problem. Current thinking about suicide emphasizes the study of psychiatric, psychological, or biological determinants. Previous work in this area has largely relied on surrogate outcomes or samples enriched for psychiatric morbidity.
To evaluate the relationship between social integration and suicide mortality.
Prospective cohort study initiated in 1988.
34 901 men aged 40 to 75 years.
Social integration was measured with a 7-item index that included marital status, social network size, frequency of contact, religious participation, and participation in other social groups. Vital status of study participants was ascertained through 1 February 2012. The primary outcome of interest was suicide mortality, defined as deaths classified with codes E950 to E959 from the International Classification of Diseases, Ninth Revision.
Over 708 945 person-years of follow-up, there were 147 suicides. The incidence of suicide decreased with increasing social integration. In a multivariable Cox proportional hazards regression model, the relative hazard of suicide was lowest among participants in the highest (adjusted hazard ratio [AHR], 0.41 [95% CI, 0.24 to 0.69]) and second-highest (AHR, 0.52 [CI, 0.30 to 0.91]) categories of social integration. Three components (marital status, social network size, and religious service attendance) showed the strongest protective associations. Social integration was also inversely associated with all-cause and cardiovascular-related mortality, but accounting for competing causes of death did not substantively alter the findings.
The study lacked information on participants’ mental well-being. Some suicides could have been misclassified as accidental deaths.
Men who were socially well-integrated had a more than 2-fold reduced risk for suicide over 24 years of follow-up.
National Institutes of Health and Robert Wood Johnson Foundation.
Suicide is a major cause of death and is increasing in incidence, especially among middle-aged men. Identify-ing modifiable risk factors might lead to effective interventions.
In a 24-year prospective cohort study, middle-aged men were less likely to commit suicide if they scored highly on measures of social integration. Marriage, frequent attendance at religious services, and having a large social network seemed especially protective.
Participants were born between 1913 and 1948. Types and amounts of social interaction among men born more recently may differ from those of earlier generations.
The degree of social integration should be considered in studies of suicide.
Appendix Table 1. Social Integration Index
Table 1. Baseline Sample Characteristics, by Social Integration Category Measured in 1988*
Table 2. Suicides During 1988–2012
Cumulative incidence of suicide, by social integration category measured in 1988.
Table 3. Relative Hazard Ratios for Suicide During 1988–2012, by Social Integration Category Measured in 1988
Table 4. Relative Hazard Ratios for Suicide During 1996–2012, by Social Integration Trajectory From 1988 to 1996
Table 5. Relative Hazard Ratios for Suicide During 1988–2012, by Social Integration Components Measured in 1988
Appendix Table 2. Relative Hazard Ratios for Suicide During 1988–2012, by Social Integration Category Measured in 1988: Sensitivity Analysis
Appendix Table 3. Deaths During 1988–2012, by Social Integration Category Measured in 1988
Appendix Table 4. Relative Hazard Ratios for Competing Mortality Outcomes During 1988–2012, by Social Integration Category Measured in 1988
Appendix Table 5. Relative Hazard Ratios for Competing Mortality Outcomes During 1988–2012, by Social Integration Category Measured in 1988: Participants With Any History of Cancer or Serious Cardiovascular Condition at Baseline Excluded
Appendix Table 6. Subdistribution Relative Hazard Ratios for Suicide During 1988–2012, Accounting for Competing Mortality Risks
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Tsai AC, Lucas M, Sania A, Kim D, Kawachi I. Social Integration and Suicide Mortality Among Men: 24-Year Cohort Study of U.S. Health Professionals. Ann Intern Med. 2014;161:85–95. doi: 10.7326/M13-1291
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Published: Ann Intern Med. 2014;161(2):85-95.
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