New research explores how your mental state affects the length of your physical one.
It all felt like too much, and I began to wonder how much of a toll this mental state has taken on my physical health. People have long suspected that chronic psychological stress impairs health and accelerates the aging process, but the mechanism behind this link had long been unknown.
The connection has become much clearer in recent years as researchers have ascertained that stress impairs telomeres — the DNA-protein complexes that cap the ends of chromosomes, protect their structural integrity, and largely control how the body ages. Telomeres shorten each time a cell divides, and shorter telomere length is linked to higher mortality rates and a higher risk of chronic diseases. Scientists have known for a while telomeres naturally become shorter as we age, but they now know that stress can accelerate this shortening.
A study comparing women who care for either a chronically ill or a healthy child found dramatic differences between the telomeres of each group. The women with an ill child felt more stressed, and women with the highest levels of perceived psychological stress — regardless of their child’s health — had significantly shorter telomeres compared to women with the lowest levels of perceived stress. Based on telomere length alone, these women had aged an additional 10 years.
The more stressed women also had decreased levels of telomerase — an enzyme that replenishes and protects telomeres — and greater levels of oxidative stress, representing an accumulation of unstable molecules that can cause DNA damage and has been shown to hasten the shortening of telomeres. These findings provided the first evidence of the cellular mechanism underlying the link between chronic psychological stress and health problems, according to the study’s authors.
Stress doesn’t prematurely age just mothers. Caregivers for Alzheimer's patients, for instance, respond to stress similarly. Researchers at Ohio State University found a connection between the chronic stress that the caregivers experienced and shorter telomeres, and they estimated that the caregivers had aged an additional four to eight years compared to non-caregivers matched for age and gender. In addition, the caregivers experienced twice the level of depression symptoms and had fewer lymphocytes — white blood cells that fight disease.
What stress does, exactly, to trigger these changes in the body has been a mystery. Scientists had hypothesized that hormones might play a role. Last year, researchers at University of California, Los Angeles, showed this to be true. The researchers determined that cortisol, a hormone that supports a fight-or-flight response, can wear down the immune system by suppressing the ability of the immune cells to activate their telomerase enzymes. This finding appears to explain why chronic stress leads to shorter telomeres and why people who are stressed are more susceptible to illness, according to the authors.
A shift is now on in this area of research. Scientists are moving away from studying the causative mechanism and toward finding ways to slow the weakening of the immune system in highly stressed people. They would like to find drugs that activate the telomerase enzyme enough to prevent an over-shortening of telomeres.
One small study led by diet guru Dean Ornish has recently indicated that simple lifestyle changes — such as eating a healthy diet and practicing moderate exercise and relaxation techniques — might help. Study participants who followed such lifestyle changes for three months experienced improved cellular telomerase activity and telomere maintenance capacity in their immune system cells.
When it comes to health, it always seem to come back to this same old “lifestyle” fix, doesn’t it? I can’t reverse the impact of yet another year’s passing, but this finding gave me hope that a stressful year would not hurt me too much. I just had to eat right, exercise, and relax a little. Sounds so simple! But lifestyle changes like these are notoriously difficult to achieve. Maybe staring down 40 will give me some added incentive. • 3 June 2009
REFERENCES: “Accelerated telomere shortening in response to life stress.” Epel ES, Blackburn EH, Lin J, et al. Proc Natl Acad Sci U S A. 2004;101:17312-5. “Accelerated telomere erosion is associated with a declining immune function of caregivers of Alzheimer's disease patients.” Damjanovic AK, Yang Y, Glaser R, et al. J Immunol. 2007;179:4249-54. “Reduced telomerase activity in human T lymphocytes exposed to cortisol.” Choi J, Fauce SR, Effros RB. Brain Behav Immun. 2008;22:600-5. “Increased telomerase activity and comprehensive lifestyle changes: a pilot study.” Ornish D, Lin J, Daubenmier J, et al. Lancet Oncol. 2008;9:1048-57.
Jennifer Fisher Wilson is the science reporter for Annals of Internal Medicine. Her stories are available at www.annals.org.