An integrative review of factors associated with telomere length and implications for biobehavioral research

Abstract

Background: Although telomere shortening occurs as a natural part of aging, there is now a robust body of research that suggests that there is a relationship between psychosocial, environmental, and behavioral factors and changes in telomere length. These factors need to be considered when integrating telomere measurement in biobehavioral research studies.

Objectives: This article provides a brief summary of the known facts about telomere biology and an integrative review of current human research studies that assessed relationships between psychosocial, environmental, or behavioral factors and telomere length.

Methods: An integrative review was conducted to examine human research studies that focused on psychosocial, environmental, and behavioral factors affecting telomere length and telomerase activity using the electronic databases PubMed/Medline and CINAHL from 2003 to the present. In addition to the known individual factors that are associated with telomere length, the results of the integrative review suggest that perceived stress, childhood adversities, major depressive disorder, educational attainment, physical activity, and sleep duration should also be measured.

Discussion: Multiple factors have been shown to affect telomere length. To advance understanding of the role of telomere length in health and disease risk, it will be important to further elucidate the mechanisms that contribute to telomere shortening.

FIGURE 1

Telomere biology. The telomere protects adjacent chromosomes by creating a cap at the end in conjunction with specialized proteins to compose a telomere-shelterin complex. In humans, the telomere is composed of arrays of guanine-rich base pair repeats that terminate with a 3′ single-stranded DNA overhang, known as the G-tail. When the cell is not undergoing mitosis, the double-stranded DNA forms a loop structure called a telomere loop (T-loop). At the very end of the T-loop, the single-stranded telomere DNA is bound to a region of double-stranded DNA to form the displacement loop (D-loop). The T-loop and D-loop are stabilized by telomere-binding proteins, which are collectively referred to as the shelterin complex. Proteins of the shelterin complex include telomeric repeat binding factor 1 (TRF1) and 2 (TRF2), protein protection of telomeres 1 (POT1), repressor activator protein 1 (Rap1), tripeptidyl peptidase 1 protein (TPP1), and TRF1-interacting nuclear factor 2 (TIN2). With telomere shortening, these proteins cannot be recruited to form the T-loops, thus leaving the chromosome ends uncapped and vulnerable to erosion and fusion. ©iStockphoto.com/Virginia Commonwealth University.

FIGURE 2

Literature review process.

FIGURE 3

Model for the study of telomere length in biobehavioral research. This model is adapted from the general biobehavioral model developed out of the ongoing work in the Center for Biobehavioral Clinical Research at Virginia Commonwealth University School of Nursing (P20 NR008988, McCain; P30 NR011403, Grap). The model includes individual factors that influence telomere length, psychosocial, environmental and behavioral factors associated with telomere maintenance and attrition, and health outcomes.