[en] Objective: To explore the effect of long-term low dose ionizing radiation on telomere length in adults. Methods: Forty female residents aged more than 55 years old from high level natural background radiation area in Yangjiang city and forty age-matched female residents from control area in Enping city were selected by quota sampling as high background group and control group, respectively. Genomic DNA was isolated from their peripheral blood. Telomere length was determined using real time q-PCR. The t-test was used to compare the square roots of the means of two groups. The individuals were divided into four groups based on ages (55-, 60-, 65- and ≥ 70) and four groups based on BMI (< 18.5, 18.5-23.99, 24.0-27.99 and ≥ 28.0). After adjusting age and BMI, multivariate linear regression analysis was performed to study the relationship between telomere length and cumulative exposure dose. The individuals were divided into longer telomere length group (≥ 2) and shorter telomere length group (< 2). Logistic regression analysis was performed to study the relationship between telomere length and cumulative exposure dose. Results: The average cumulative dose was(169.52 ± 27.43) mSv for high background group and (47.52 ± 6.50) mSv for control group. The telomere length of high background group was (1.98 ± 1.25), shorter than that of control group (2.69 ± 1.44) with statistically significant difference(t = 2.24, P < 0.05). The multivariate linear regression analysis revealed that the effect of cumulative dose on telomere length was not significant (P > 0.05). Association between telomere length and cumulative dose was explored through Logistic regression, and odds ratio was taken as 0.992(95% CI, 0.985-0.999). There was a weak inverse association between telomere length and cumulative dose, because the odds ratio (OR) was very close to 1. Conclusions: No obvious dose-effect relationship between telomere length of residents and cumulative radiation doses was found. But the long-term low dose ionizing radiation may lead to the shortening of the telomere length in adults. (authors)