Brief report
Obesity, unexplained weight loss and suicide: The original Whitehall study

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Abstract

Background

Evidence on the association between obesity and suicide is mixed. However, the strength of obesity as a predictor of suicide may be reduced, because of the role of weight changes associated with mental disorders. We tested the hypothesis that both obesity and unexplained weight loss are related to elevated suicide risk.

Methods

A clinical examination with measurements of height, weight and self-reported unexplained weight loss was conducted at baseline for 18,784 men aged 40 to 69. Based on national mortality register data, 61 suicides were identified during the 38-year follow-up.

Results

The age-adjusted hazard ratio for suicide among obese versus normal weight men was 2.22 (95% CI 0.94 to 5.28). Additional adjustment for unexplained weight loss raised this ratio to 2.48 (95% CI 1.04 to 5.92). Unexplained weight loss was associated with a substantial excess risk of suicide irrespective of obesity (age-adjusted hazard ratio 5.38, 95% CI 2.31 to 12.50; age- and obesity-adjusted hazard ratio 5.58, 95% CI 2.37 to 13.13).

Limitations

Inability to take into account the effect of depression as a potential mediating mechanism.

Conclusions

This study provides evidence that both obesity and unexplained weight loss may be important predictors of suicide. Lack of adjustment for weight loss may suppress the observed association between obesity and suicide.

Introduction

While several studies have found an elevated suicide risk among obese people (body mass index (BMI)  30 kg/m2) (Dong et al., 2006, Eaton et al., 2005, Pompili et al., 2006), there are notable exceptions reporting no or even inverse associations between obesity and suicide risk (Mangnusson et al., 2006, Mukamal et al., 2007). Reasons for mixed findings have remained unclear. We hypothesise that failure to take into account the role of weight changes has contributed to inconclusive findings. The rationale for our hypothesis comes from the central role of mental disorders in suicidal behavior. Both clinical and epidemiologic studies suggest a positive link between obesity and depression (Faith et al., 2002, McElroy et al., 2004, Simon et al., 2006). However, studies also show depressive episodes to be associated with weight loss reducing prevalence of obesity among people at elevated risk of suicide (Yorbik et al., 2004). Given this, the strength of current BMI as a predictor of suicide may be reduced in observational data, because of the frequency with which unexplained weight loss is associated with mental disorders. In this study, we examine associations of obesity and unexplained weight loss with risk of suicide mortality in a large occupational cohort, the Whitehall study. We hypothesise that lack of adjustment for weight loss suppresses the observed association between obesity and suicide.

Section snippets

Study population

Data were collected on 19,019 non-industrial London-based male government employees aged 40 to 69 years at screening between September 1967 and January 1970 (response rate 74%). Screening involved the completion of a study questionnaire and participation in a medical examination. Mortality records up to 2005 were successfully flagged for 18,863 men (99.2%). Three men with missing BMI measurements, 32 with missing data for weight loss, and 44 with an unknown cause of death, were excluded from

Results

As shown in Table 1, 4.3% were obese and 2.2% reported unexplained weight loss over the past year among the 18,784 men. Table 2 presents the age-adjusted hazard ratios for each BMI category and weight loss in relation to suicide mortality. The hazard ratio for suicide in obese versus normal weight men was 2.22 (95% CI 0.94 to 5.28) suggesting an excess but statistically non-significant risk. The age-adjusted hazard ratio of suicide mortality in men with unexplained weight loss versus men with

Discussion

In this prospective cohort study of male civil servants, obesity and unexplained weight loss were both independently associated with an increased risk of suicide mortality. The association between obesity and suicide slightly strengthened when adjusted for unexplained weight loss. Our results should be considered as preliminary due to the small number of suicides. However, they provide support for the possibility that weight change, and particularly unexplained weight loss, may suppress any

Role of funding source

The Whitehall II study has been supported by grants from the Medical Research Council; British Heart Foundation; Health and Safety Executive; Department of Health; National Heart Lung and Blood Institute (HL36310), US, NIH: National Institute on Aging (AG13196), US, NIH; Agency for Health Care Policy Research (HS06516); and the John D and Catherine T MacArthur Foundation Research Networks on Successful Midlife Development and Socio-economic Status and Health and the Academy of Finland (project

Conflict of interest

All other authors declare that they have no conflicts of interest.

Acknowledgments

We thank all participating Civil Service departments and their welfare, personnel, and establishment officers; the Occupational Health and Safety Agency; the Council of Civil Service Unions; all participating civil servants in the Whitehall II study; all members of the Whitehall II study team.

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    However, data in the study do not allow one to discern whether BMI in these individuals was low throughout life or whether other specific medical or psychiatric factors contributed to being underweight proximal to the time of suicide. Research attempting to explain the relationship between weight changes and suicide has found that unexplained weight loss, in at least in one study, was associated with an increased risk of suicide (Eloviano et al., 2009). It is also possible that having a medical condition may have conferred risk of suicidal behavior and suicide death in these individuals (independently of being underweight).

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