Research Article
Smoking and the Reduced Life Expectancy of Individuals With Serious Mental Illness

https://doi.org/10.1016/j.amepre.2016.06.007Get rights and content

Introduction

People with serious mental illness experience substantially reduced life expectancy, likely due in part to their higher smoking rates relative to the general population. However, the extent to which smoking affects their life expectancy, independent of mental illness, is unknown. This study quantifies the potential contribution of smoking to reduced life expectancy among individuals with serious psychological distress (SPD), a measure that screens for serious mental illness in national surveys.

Methods

A cohort of 328,110 U.S. adults was examined using the 1997–2009 National Health Interview Surveys linked to the 2011 National Death Index. Cox models were used to estimate mortality hazard ratios for current smoking, former smoking, and SPD and construct life tables by smoking and SPD status. The smoking-attributable fraction of deaths by SPD status was calculated. Analyses were conducted in 2015.

Results

Among those with SPD, being a current smoker doubles the risk of death. Current smokers with SPD lose 14.9 years of life relative to never smokers without SPD. Among never smokers, having SPD reduces life expectancy by 5.3 years. Thus, smoking may account for up to two thirds of the difference in life expectancy between smokers with SPD and never smokers without SPD. One third of deaths among those with SPD can be attributed to smoking.

Conclusions

The life expectancy difference between current smokers with SPD and never smokers without SPD is primarily due to smoking. Aiding individuals with serious mental illness to avoid smoking will translate into sizeable gains in life expectancy.

Introduction

The annual risk of death for individuals with psychiatric disorders is more than twice that of the general population.1 Those with mental illness lose 10 years of potential life on average1 and their quality of life is reduced by the contribution of these disorders to overall disability.2 Many with serious mental illness die from unnatural causes such as suicide or accidents. High levels of psychological distress are associated with suicide ideation and completion,3, 4 and more than 40,000 U.S. deaths are due to suicide each year.5 However, a large proportion of deaths among those with psychiatric disorders is ultimately due to chronic diseases such as heart disease, cancer, and stroke.6

This poor physical health is attributed to a combination of factors.7, 8, 9 Those with serious mental illness are disproportionately living in poverty or lack housing, and are subject to health risks associated with social deprivation. Patients with psychiatric disorders are less likely to receive adequate physical health care than the mentally healthy. Some antipsychotic medications come with hazardous side effects. Finally, those with serious mental illness are more likely to engage in harmful health behaviors such as poor diet, alcohol or substance abuse, and smoking.6, 10, 11, 12, 13, 14

Both substantial burdens to health, serious mental illness and smoking are highly associated with each other.2, 15, 16 Serious mental illness can be broadly defined as having at least one DSM-IV diagnosis and functional impairment in the past 12 months.17 National surveys screen for serious mental illness using the Kessler six-item scale for non-specific serious psychological distress (SPD). High scores significantly predict DSM-IV diagnoses, such as bipolar disorder and major depressive disorder, with associated impairment.17, 18, 19 Like diagnosable psychiatric disorders, SPD is highly associated with increased mortality and comorbidity with smoking.20, 21, 22 Approximately 42% of adults with SPD are current smokers.21 This is lower but on the same order of magnitude as smoking prevalence among those with bipolar disorder (46%) and schizophrenia (59%).23 Overall adult smoking prevalence in the U.S. is less than 20%.24

Although tobacco use contributes to early death among those with psychiatric disorders, the extent to which smoking affects excess mortality, independent of mental illness, is unknown. Several mortality studies comparing populations with and without psychiatric disorders adjust for confounding due to smoking but are restricted to veterans,25, 26 California-based or non-U.S. patient populations,6, 27 and middle-aged or elderly individuals.28, 29, 30, 31 These studies show that psychiatric disorders increase mortality risk even after accounting for smoking, but have not quantified the specific contribution of smoking to mortality relative to mental illness.

This study uses nationally representative data to estimate:

  • 1

    the relative rates of death for smoking and SPD adjusting for covariates; and

  • 2

    the impact of smoking on all-cause mortality and life expectancy among people with and without SPD in the U.S.

Section snippets

Data Source and Measures

The National Health Interview Survey (NHIS) surveys the civilian, non-institutionalized U.S. population. Since 1997, NHIS has identified adults with SPD by asking respondents about the frequency over the past month with which they have felt:

  • 1.

    nervous;

  • 2.

    hopeless;

  • 3.

    restless or fidgety;

  • 4.

    so sad or depressed that nothing could cheer them up;

  • 5.

    that everything is an effort; and

  • 6.

    worthless (Kessler six-item scale).

Each item is scored 0–4 based on the response none of the time, a little of the time, some of the

Results

Table 1 presents study population characteristics according to SPD status. People with SPD comprised 3.1% of the population. From 1997 to 2011, 38,266 participants (9.5%) died at follow-up, including 15.4% of individuals with SPD and 9.2% of individuals without SPD. Average follow-up time was 8.2 years. Mean age at baseline was 49.5 years and 49.8 years for the SPD and non-SPD samples, respectively. Participants with SPD were significantly more likely to be smokers, less likely to have quit,

Discussion

This study adds to the literature by quantifying the potential contribution of smoking to reduced life expectancy among people with serious mental illness. The findings that mental illness and smoking both independently reduce life expectancy corroborate previous research.1, 41 Smoking may account for up to two thirds of the difference in life expectancy between current smokers with SPD and never smokers without SPD, independently contributing to as much as 9.6 years of potential life lost,

Conclusions

The need to effectively address smoking among mentally ill populations is critical.50, 51, 52 Global disparities in smoking, mortality, and life expectancy outcomes by mental health status have persisted for decades. Although smoking rates have declined substantially for the general U.S. population, comparable declines have not been observed among those with mental illness.53 People with mental illness continue to smoke at higher rates, with greater intensity, and with less success in quitting.

Acknowledgments

No financial disclosures were reported by the authors of this paper.

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