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Telomere length and work schedule characteristics in the NIEHS sister study.

Parks-CG; McCanlies-EC; Miller-DB; Cawthon-RM; DeRoo-LA; Sandler-DB
Occup Environ Med 2007 Dec; 64(12):e21
Objectives: Telomeres are protective DNA sequences on the ends of chromosomes, which can shorten with repeated cell replication and contribute to senescence. Shorter telomere length has been associated with chronic stress, age and obesity in women, and with metabolic and cardiovascular disease outcomes. In combination with lifestyle and socioeconomic factors, work schedule may be a source of occupational stress in women. We hypothesised that cumulative lifetime years of full-time and over-time work, rotating shiftwork or irregular hours, may be related to shorter telomere length in women. Methods: Average leukocyte telomere length was estimated by quantitative PCR on a sample of 677 women selected for a study of biomarkers and perceived stress in the NIEHS Sister Study cohort (median age 55, range 35-75). Questionnaire data included lifetime job history and work schedule for each job reported. Age-adjusted regression models estimated associations with telomere length. We also examined whether associations were mediated or modified by education, age, and risk factors such as inadequate sleep, elevated stress and body mass index. Results: Currently holding a full-time job and years of full-time work were significantly associated with shorter telomere length (b =20.003 per year, p = 0.002) independent of the effects of age (b =20.006 per year, p,0.0001). These findings persisted in women currently working at enrolment and were not confounded by education, current sleep, BMI, perceived stress, smoking and health status. The odds of being in the shortest quartile of telomere length increased with increasing years of fulltime work among women over age 55 (OR 3.4; 95% CI 1.4 to 8.2; >24.5 years vs ,5.2 years), those with higher than average perceived stress (OR 3.7; 95% CI 1.5 to 9.3) and those with some college or a bachelors degree (OR 5.7; 95% CI 1.9 to 16.7) but not higher levels of education. Years in jobs characterised as over-time, shift-work and irregular hours were not consistently related to telomere length. Conclusion: Telomere length may be associated with lifetime years of fulltime work in some women. Further investigation is needed to understand the contribution of job strain, work-life balance and socioeconomic factors. Telomere length may provide a novel biomarker for studies of chronic occupational stress.
DNA-damage; Demographic-characteristics; Statistical-analysis; Epidemiology; Stress; Physiological-stress; Psychological-stress; Humans; Women
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Occupational and Environmental Medicine