I came across a paper recently that combines two research areas that I find extremely interesting: the use of salivary telomere length (TL) as a biomarker to predict biological age, and the psychological and physiological effects of negative stress on health and longevity. The paper, titled Marital disruption is associated with shorter salivary telomere length in a probability sample of older adults by Mark Whisman et al. (2016), explores the hypothesis that marital disruption accelerates cellular aging as characterized by salivary TL. This exciting paper explores the themes of salivary telomere utility in study design, as well as the long-term consequences of stressful life events.
Telomeres are DNA-protein structures that protect the ends of chromosomes and maintain DNA integrity during cell division. Each time a cell divides, telomeres naturally shorten. Over time, the shortened telomeres have a diminished ability to protect the chromosome, which leads to chromosomal instability and cell death. At birth, telomere length varies among individuals suggesting a genetic or hereditary component. Similarly, during ones life, the rate at which the telomeres shorten varies. Telomere shortening is considered a biological predictor of age since it’s a measure of cellular aging.
Significant research is dedicated to understanding the relationship between risk factors and their downstream effects, like whether a stressful life event may increase the risk of developing a disease later in life. Telomeres naturally shorten over time, but many physiological, psychological, psychosocial and genetic factors may influence the rate in which they shorten, enabling researchers to use TL as a surrogate marker for longevity and health. Furthermore, using salivary DNA to measure TL offers an accessible alternative to standard blood DNA. Mark Whisman chose salivary TL for his study for these exact reasons:
Salivary telomere length correlates highly with telomere length as measured by blood leukocyte and positive correlations are observed for telomere length measured in leukocytes, skeletal muscle, skin and subcutaneous fat. In addition, salivary telomere length correlates with other risk factors for adverse health outcomes (e.g., familial risk for depression; and known correlates of telomere length as measured by blood leukocytes, including age, tobacco smoking, perceived stress, other measures of adversity and disadvantage, and hypothalamic-pituitary axis (HPA) dysregulation (i.e., cortisol reactivity to stress).
For most people, the end of a marriage is a stressful event, and chronic stress has been associated with shortened TL. But what is stress? This sounds like a relatively straightforward question, but to quote Dr. Hans Selye, the pioneering Austrian-Canadian endocrinologist that coined the term ‘stress’ in 1936, “Everyone knows what stress is, but nobody really knows.” Dr. Selye defined stress as “the non-specific response of the body to any demand for change.” This broad definition encompasses both positive stress, which can result in increased productivity, as well as negative stress, which is chronic and/or overwhelming. The pivotal point where too much stress alternates from productive to negative varies among individuals. For example, rollercoasters are a type of stress than can vary by individual; either you find them enjoyable or terrifying.
Vertebrates respond to stressful situations by releasing certain hormones that elicit an increased heart rate and energy level. This fight-or-flight stress can be beneficial in the short term. Constant stress evokes a similar bodily reaction over longer time periods, but can have damaging health consequences. This means that constantly worrying about your relationship status or work problems, even while you’re comfortably at home in bed, is a self-perceived stress, and isn’t good. Dr. Robert Sapolsky, Professor of Biological and Neurological Sciences at Stanford University says, “If you get chronically, psychosocially stressed, you’re going to compromise your health, [so] essentially we’ve evolved to be smart enough to make ourselves sick.” While different personality types tend to experience varying levels of perceived stress (some of us worry more or have better coping mechanisms to deal with stress), stress can fluctuate within the same person depending on their mental outlook. Dr. Hans Selye states that “adopting the right attitude can convert a negative stress into a positive one.” Similarly, to quote Captain Jack Sparrow from the Walt Disney film Pirates of the Caribbean, “The problem is not the problem. The problem is your attitude about the problem.” Our ability to change our attitude and develop coping strategies to mitigate stress highlights the potential role of therapeutic intervention. Changing the way you think might literally prolong your life.
In the Mark Whisman study, researchers wanted to evaluate the hypothesis that “marital disruption might accelerate cellular aging, as operationalized by telomere shortening.” They hypothesized the following:
[P]eople who were separated or divorced would have shorter salivary telomeres than those who were continuously married or never married; [they] did not expect differences in salivary telomere length between people who were separated or divorced and people who were widowed, as death of a spouse is viewed as a highly stressful event.
The study involved 3526 participants drawn from the Health and Retirement Study (HRS), a multistate probability cohort of households in the United States. TL assays were performed exclusively using DNA extracted from saliva using Oragene® collection kits.
The authors discovered that marital disruption was significantly and negatively associated with salivary TL. Specifically, individuals who were previously separated or divorced had shorter salivary TL than those who were never married or continuously married. This association remained statistically significant even after adjusting for numerous confounding variables (for example, body mass index, health and lifestyle factors, socioeconomic variable, etc.). These results highlight the impact of a stressful life event on cellular aging, as well as validate the use of salivary TL as a biomarker. Although negative stress is an inevitable part of life, a growing body of studies correlating stress and adverse health outcomes suggests the importance of developing coping mechanisms to de-stress your life.
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(2) Rosch PJ. Reminiscences of Hans Selye, and the birth of "stress". Int J Emerg Ment Health. 1(1):59-66 (1999).
(3) Shwartz M (2007, March 7). Robert Sapolsky discusses physiological effects of stress. Stanford Report. Retrieved from http://news.stanford.edu.
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