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American Journal of Forensic Medicine & Pathology:
doi: 10.1097/PAF.0000000000000094
Original Articles

Body Mass Index and Suicide

Austin, Amy E. BHlthSc (Hons)*†; van den Heuvel, Corinna PhD*; Byard, Roger W. MD*†

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Author Information

From the *Discipline of Anatomy and Pathology, The University of Adelaide; and †Pathology, Forensic Science SA, Adelaide, South Australia, Australia.

Manuscript received July 8, 2013; accepted January 21, 2014.

The authors report no conflicts of interest.

Reprints: Amy E. Austin, BHlthSc (Hons), Discipline of Anatomy and Pathology, Level 3, Medical School North Bldg, The University of Adelaide, Frome Rd, Adelaide, South Australia 5005, Australia. E-mail: amy.austin@adelaide.edu.au.

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Abstract

It has been suggested that there is a connection between depression and an increased body mass index (BMI). As depression is related to suicide, a South Australian cohort study was performed to test whether a high BMI may also characterize victims of suicide. Body mass indexes from 100 consecutive cases of suicide (male-to-female ratio, 1:1) taken from the files of Forensic Science South Australia in Adelaide, Australia, were compared with BMIs from 100 sex- and age-matched control cases, where deaths were due to accidents, homicides, or natural diseases. No significant differences in BMIs and BMI categories were found between the 2 groups. However, when cases were subclassified according to the method used, BMIs were noted to be considerably lower in hangings than in both the control group as well as in victims who died of alternative means of suicide (P < 0.001). An association between an increased BMI and suicide could not be substantiated in this local study. However, the reasons for the decreased BMIs in hangings require further consideration that may assist in understanding more about particular victim subgroups.

As suicide, or the act of killing oneself, constitutes a significant component of preventable mortality in many communities,1 any potential contributing factors should be investigated. In addition to being associated with victims of suicide, depression has also been linked to a high body mass index (BMI),2–5 although the precise reasons for the latter association remain unclear,6 and it has also been termed “controversial.”7

Body mass has increased globally, with the prevalence of obesity (BMIs ≥30 kg/m2) in Australia more than doubling in 2 decades.8–10 Whereas the effects of obesity on population morbidity and mortality are well recognized,10–16 the association with mental illness is less clear-cut. Although obesity has been linked to depression,2–5 it is not known whether this is a primary or a secondary phenomenon; that is, does obesity lead to depression because of underlying metabolic and endocrine derangements, or does obesity result from depression because of reduced physical activity and/or alteration in dietary intake? However, if there is a cause-and-effect relationship, the “obesity epidemic” should be associated with a significant increase in the incidence of depressive illness and therefore also of suicide.

In order to further explore possible links between BMI and suicide in South Australia (SA), the following primary and community-based study was undertaken.

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MATERIALS AND METHODS

The pathology files at Forensic Science SA in Adelaide, Australia, were searched for 100 consecutive cases of suicide involving 50 males and 50 females, from October 2008 to December 2009. In addition, 100 sex- and age-matched controls of accidental, homicidal, or natural deaths were also selected over the same period. All victims with evidence of pregnancy, dismemberment, incineration, and/or significant postmortem changes precluding accurate measurements of weight and/or height were excluded from analyses. All cases had undergone police and coronial investigations, with formal autopsy examination. Case details were reviewed, and the sex, age, weight, and height of victims, as well as the means of suicide, were collated. Body mass indexes were calculated according to a standard formula (the weight in kilograms divided by the square of the height in meters [kg/m2])8 and were also classified as underweight (BMIs <18.5 kg/m2), normal weight (BMIs 18.5–24.9 kg/m2), overweight (BMIs 25.0–29.9 kg/m2), and obese (BMIs ≥ 30.0 kg/m2).

Forensic Science SA is the South Australian state forensic facility where medicolegal autopsies are performed at the direction of the state coroner. The population served is approximately 1.6 million.

Statistical analyses were conducted using IBM SPSS Statistics for Windows (version 18.0). Categorical variables of interest were compared via Pearson χ2 tests to determine differences by sex, manners of deaths, methods of suicide, and BMI categories. Continuous variables of interest were compared via Student paired-samples and 1-sample t tests to determine differences by BMIs, and the normality of distributions was checked via Shapiro-Wilk tests. Differences were considered statistically significant when P < 0.05.

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RESULTS

The average BMI in the suicide group was 26.6 kg/m2 (median, 25.3 kg/m2; range, 17.3–53.6 kg/m2), which was not significantly different to that of the control group with 26.8 kg/m2 (median, 26.5 kg/m2; range, 14.9–46.0 kg/m2) (P = 0.72). The average BMIs by sex in victims of suicide compared with controls is shown in Figure 1. However, after separating victims into different methods of suicide (Table 1), BMIs were found to be significantly lower in hanging deaths (mean, 24.2 kg/m2; median, 23.6 kg/m2; range, 17.3–34.3 kg/m2) than in both the control cases (mean, 27.1 kg/m2; median, 27.0 kg/m2; range, 15.8–46.0 kg/m2) and in victims who died of alternative means of suicide, including drug overdoses, carbon monoxide toxicities, plastic bag asphyxias, and jumps from heights or motor vehicle/train deaths (P < 0.001).

TABLE 1
TABLE 1
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FIGURE 1
FIGURE 1
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The sexes did not differ significantly in BMI categories (χ23 = 5.25, P = 0.15), and there were no significant differences in BMI categories between cases and controls overall (χ23 = 5.19, P = 0.16). However, significant case-control discrepancies were again observed for hangings (χ23 = 12.60, P < 0.01). The hanging group was more likely to have BMIs in the underweight and normal weight categories than controls and less likely to have BMIs in the overweight and obese categories (Fig. 2).

FIGURE 2
FIGURE 2
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DISCUSSION

Epidemiologic features of suicide vary greatly and are influenced by factors such as the sex, age, and race of victims, as well as by cultural practices and beliefs.1 The association of depressive illness with suicide is well acknowledged. However, the relationship of depression to BMI and suicide is less clear-cut. This is perhaps not surprising, given that data on the association between depression and BMI are derived from individual studies that include multiple cohorts, over varying time periods.

In the current study, no significant differences in BMIs could be demonstrated between local suicide victims and those who had died of accidents, homicides, or natural diseases (Fig. 1). In fact, once the suicide cases had been subdivided according to the method used, it became clear that those who had died of hanging had significantly lower BMIs than both the control group (Fig. 2 and Table 1) and other victims of suicide (Table 1).

Suicidal behavior and, in particular, methods of suicide vary among and even within populations.1,17 Factors that influence the choice of method include knowledge of the particular lethal effects of a substance or activity and the availability of the material or device that is being used.18–21 While the methods of suicide that require physical effort and agility may not be accessible to individuals with markedly increased BMIs, no significant differences in BMIs could be demonstrated among the suicide victims overall (Fig. 1), except for the hanging group (Fig. 2 and Table 1). Although the reasons for the significantly lower BMIs in hangings compared with control cases and other victims of suicide are not determinable from the present study, such discrepancies may be related to disordered eating, including reduced appetites and thus reduced dietary intakes associated with depressive illnesses and/or possible drug and/or alcohol abuse.

Further problems may occur in the overall assessment of suicides if available data for attempted suicides are relied on. Factors of concern include how and when a record of BMI and/or a suicide attempt was obtained, particularly if this was not immediately before the nonfatal episode or was self-reported. This may result in substantial discrepancies, as well as biased analyses and interpretations. Also, large sample sizes do not necessarily equate to population-based or representative studies, as selected samples or inadequate secondary data sources may mask or overlook critical case details.

In this primary study, the failure to show higher BMIs in suicide cases would be in keeping with the assertion that the association between depression and obesity is neither strong nor simple.6 In fact, the finding of significantly lower BMIs in hanging cases is more in line with a recent cross-sectional study that demonstrated that the obesity-associated gene (FTO rs9939609 polymorphism), which has been identified as a major contributor to obesity in European populations, actually protects against significant depression.7 The discovery of considerably lower BMIs in local hanging deaths once the suicide group had been subdivided according to method suggests a complex interaction that warrants further investigations that may assist in understanding more about specific victim subgroups. This particular finding also reinforces the suggestion that the pooling of subjects may mask critical factors and variables.6

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REFERENCES

1. Austin AE, van den Heuvel C, Byard RW. Suicide in forensic practice—an Australian perspective. Aust J Forensic Sci. 2011; 43: 65–76.

2. Atlantis E, Goldney RD, Eckert KA, et al. Trends in health-related quality of life and health service use associated with body mass index and comorbid major depression in South Australia, 1998–2008. Qual Life Res. 2012; 21: 1695–1704.

3. Bruffaerts R, Demyttenaere K, Vilagut G, et al. The relation between body mass index, mental health, and functional disability: a European population perspective. Can J Psychiatry. 2008; 53: 679–688.

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5. Roberts RE, Deleger S, Strawbridge WJ, et al. Prospective association between obesity and depression: evidence from the Alameda County study. Int J Obes Relat Metab Disord. 2003; 27: 514–521.

6. Faith MS, Matz PE, Jorge MA. Obesity-depression associations in the population. J Psychosom Res. 2002; 53: 935–942.

7. Samaan Z, Anand S, Zhang X, et al. The protective effect of the obesity-associated rs9939609 A variant in fat mass- and obesity-associated gene on depression. Mol Psychiatry. 2013; 18: 1281–1286.

8. Byard RW, Bellis M. Significant increases in body mass indexes (BMI) in an adult autopsy population from 1986 to 2006—implications for modern forensic practice. J Forensic Leg Med. 2008; 15: 356–358.

9. Colagiuri S, Lee CM, Colagiuri R, et al. The cost of overweight and obesity in Australia. Med J Aust. 2010; 192: 260–264.

10. Walls HL, Wolfe R, Haby MM, et al. Trends in BMI of urban Australian adults, 1980-2000. Public Health Nutr. 2010; 13: 631–638.

11. Byard RW. The complex spectrum of forensic issues arising from obesity. Forensic Sci Med Pathol. 2012; 8: 402–413.

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14. Prospective Studies Collaboration, Whitlock G, Lewington S, et al. Body-mass index and cause-specific mortality in 900 000 adults: collaborative analyses of 57 prospective studies. Lancet. 2009; 373: 1083–1096.

15. Faeh D, Braun J, Tarnutzer S, et al. Obesity but not overweight is associated with increased mortality risk. Eur J Epidemiol. 2011; 26: 647–655.

16. Song X, Pitkäniemi J, Gao W, et al. Relationship between body mass index and mortality among Europeans. Eur J Clin Nutr. 2012; 66: 156–165.

17. Byard RW, Houldsworth G, James RA, et al. Characteristic features of suicidal drownings: a 20-year study. Am J Forensic Med Pathol. 2001; 22: 134–138.

18. Byard RW, Markopoulos D, Prasad D, et al. Early adolescent suicide: a comparative study. J Clin Forensic Med. 2000; 7: 6–9.

19. Byard RW, Hanson KA, James RA, et al. Suicide methods in the elderly in South Australia 1981–2000. J Clin Forensic Med. 2004; 11: 71–74.

20. Austin AE, van den Heuvel C, Byard RW. Causes of community suicides among indigenous South Australians. J Forensic Leg Med. 2011; 18: 299–301.

21. Byard RW, Klitte Å, James RA, et al. Changing patterns of female suicide: 1986–2000. J Clin Forensic Med. 2004; 11: 123–128.

Keywords:

suicide; hanging; depression; body mass index; obesity

Copyright © 2014 by Lippincott Williams & Wilkins

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