Clinical Briefs: Stress Doesn't Cause Cancer (But It Might Kill You)
With Comments from Russell H. Greenfield, MD. Dr. Greenfield is Medical Director, Carolinas Integrative Health, Carolinas HealthCare System, Charlotte, NC, and Clinical Assistant Professor, School of Medicine, University of North Carolina, Chapel Hill, NC.
Source: Nielsen NR, et al. Self reported stress and risk of breast cancer: Prospective cohort study. BMJ 2005;331:548. Epub 2005 Aug 15.
Goal: To explore the relationship between everyday stress (as opposed to the acute stress of major life events) on the long-term risk of first time incidence of primary breast cancer.
Study Design: Prospective, longitudinal cohort study (the Copenhagen City heart study) with 18 years of follow-up.
Subjects: Danish women initially randomized to participate in the Copenhagen City heart study in 1976 (additional questions were asked of 6,689 women in 1981-1983 [age range 21-91 years], forming the basis of the study reviewed here).
Methods: At the time of secondary evaluation (1981-1983), subjects were asked about their level of stress with regard to intensity and frequency, with results classified as low, medium, and high stress. Subjects were then followed until the date of first diagnosis of primary breast cancer, death, emigration, or the end of follow-up in 1999. The main outcome measure was first time incidence of primary breast cancer.
Results: Ten percent of participants reported high levels of stress, and a higher percentage of women in this group died during follow-up as compared with women in the moderate or low stress groups; however, the risk for development of breast cancer was inversely proportional to both stress intensity and stress frequency. For every increase in stress level on the stress scale employed there was an 8% decreased risk of development of primary breast cancer. The relationship between stress and decreased risk for breast cancer was most notable among women receiving hormone replacement therapy.
Conclusion: High levels of self-reported stress are associated with a lower risk of development of breast cancer over 18 years of follow-up.
Study strengths: Sample size; linkage to civil registry ensuring high degree of follow-up (< 0.1% lost to follow-up) and identification of all cases of breast cancer; prospective design.
Study weaknesses: Single point of measurement applied to 18 years of follow-up (life being dynamic, it is likely there was a change in stress status for most participants over the period of follow-up); data on specific risk factors for breast cancer, including family history, were not obtained.
Of note: Various studies using different designs have examined the potential relationship between acute or daily stress and development of breast cancer, and have produced conflicting results; for the purposes of the study, stress was defined as a feeling of tension, nervousness, impatience, anxiety, or sleeplessness; follow-up was ensured using the civil registry number unique to each Danish citizen; no stress effect was noted in subgroups that included menopausal status, number of children, and alcohol consumption; more women in the high stress group received hormone replacement therapy, had less education and high alcohol intake, and were physically inactive compared with women in the other two groups.
We knew that: In animal studies, stress has been shown to decrease estrogen synthesis, which could explain a reduced rate of breast cancer development (stress can affect signals coming from the hypothalamic-pituitary-gonadal axis by activating the hypothalamic-pituitary-adrenal axis and the sympathetic nervous system); persistent, low-level everyday stress results in sustained activation of stress hormones, possibly resulting in decreased estrogen production (thereby lowering risk of development of breast cancer); persistent daily stress may affect health indirectly through negative changes in personal behaviors; the nature of stressful life events differs significantly from that of sustained everyday stress; research on the health impact of stress has thus far focused more on external stressors and less on the individual's perception of stress.
Comments: Practitioners often encounter people who received a diagnosis of significant illness within months of a major negative life event, such as the loss of a loved one, yet existing data do not consistently point to an increased risk of infirmity with acute, major stress. Practitioners also frequently encounter people living with high levels of stress on a daily basis, many of whom suffer with chronic maladies like pain, autoimmunity, anxiety, or frequent infections. While the intensity and frequency of everyday stress may not correlate with breast cancer development, ample data exist showing an association of sustained stress with inflammation, mood disorders, and worse prognosis in the setting of established cardiovascular disease. Each person, practitioner and patient alike, experiences stress to varying degrees. Though everyday stress may have no impact on the development of cancer, part of the role of a healthcare provider is to ensure that patients possess adequate means to effectively manage stress, if only to live longer and at peace. As health care practitioners, we should be role models in this regard.
What to do with this article: Keep a hard copy in your file cabinet.
Greenfield RH. Stress doesn't cause cancer (but it might kill you). Altern Med Alert 2005;8(10):119-120.You have reached your article limit for the month. Subscribe now to access this article plus other member-only content.
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