Age-at-exposure effects on risk estimates for non-cancer mortality in the Japanese atomic bomb survivors

Shape of radiation dose response relationship for ischaemic heart disease mortality and its interpretation: analysis of the national registry for radiation workers (NRRW) cohort

Statistically significant increases in ischemic heart disease (IHD) mortality with cumulative occupational external radiation dose were observed in the National Registry for Radiation Workers (NRRW) cohort. There were 174 541 subjects in the NRRW cohort. The start of follow up was 1955, and the end of the follow-up for each worker was chosen as the earliest date of death or emigration, their 85th birthday or 31 December 2011. The dose-response relationship showed a downward curvature at a higher dose level >0.4 Sv with the overall shape of the dose-response relationship best described by a linear-quadratic model. The smaller risk at dose >0.4 Sv appears to be primarily associated with workers who started employment at a younger age (<30 years old) and those who were employed for more than 30 years. We modelled the dose response by age-at-first exposure. For the age-at-first exposure of 30+ years old, a linear dose-response was the best fit. For age-at-first exposure <30 years old, there was no evidence of excess risk of IHD mortality for radiation doses below 0.1 Sv or above 0.4 Sv, excess risk was only observed for doses between 0.1-0.4 Sv. For this age-at-first exposure group, it was also found that the doses they received when they were less than 35 years old or greater than 50 years old did not contribute to any increased IHD risk.

Differential effect of ionizing radiation exposure on multipotent and differentiation-restricted bone marrow mesenchymal stem cells

Debilitating effects of bone marrow from ionizing radiation exposure has been well established for hematopoietic stem cells; however, radiation toxicity of mesenchymal stem cells (MSCs) has been controversial. The present study addressed if ionizing radiation exposure differently affected bone marrow MSCs with various differentiation commitments. Mouse bone-marrow-derived MSCs, D1 cells of early passages (≤ 5 passages; p5) maintained the complete characteristics of multipotent MSCs, whereas, after ≥ 45 passages (p45) the differentiation capability of D1 cells became partially restricted. Both p5 and p45 D1 cells were subjected to single dose irradiation by radioactive isotope (137)Cs. Radiation treatment impaired cell renewal and differentiation activities of p5 D1 cells; however, p45 D1 cells were less affected. Radiation treatment upregulated both pro- and anti-apoptotic genes of p5 D1 cells in a dose-dependent manner, potentially resulting in the various apoptosis thresholds. It was found that constitutive as well as radiation-induced phosphorylation levels of histone H2AX was significantly higher in p45 D1 cells than in p5 D1 cells. The increased repair activity of DNA double-strand breakage may play a role for p45 D1 cells to exhibit the relative radioresistance. In conclusion, the radiation toxicity predominantly affecting multipotent MSCs may occur at unexpectedly low doses, which may, in part, contribute to the catabolic pathology of bone tissue.

Mean excitation energies and energy deposition characteristics of bio-organic molecules

We suggest a method for determination of the mean excitation energies of several biomolecules, such as amino acids, using a Bragg-like sum rule developed for molecular fragments or functional groups. Because the fragment composition of many bio-organic molecules is very similar, we find that many of them, including the amino acids, have similar mean excitation energies (approximately 70 eV, which is interestingly close to the mean excitation energy of the major component of a cell: namely, water). Differences in amino acid mean excitation energies arise from variation of the side chains (-R); addition of -CH(2)- groups decreases the mean excitation energy.

All-cause mortality in the Aberdeen 1921 birth cohort: effects of socio-demographic, physical and cognitive factors

BACKGROUND

Childhood intelligence predicts mortality throughout most of the life span. However, it is unknown whether its effect persists into advanced old age.

METHODS

The Aberdeen Birth Cohort born in 1921 (n = 354) and that had an IQ test as part of the national Scottish Mental Survey of 1932 were seen in 1997 at age 76 years when childhood and adult socio-environmental, medical and cognitive data were collected. Participants were followed until May 2007 and vital status determined from the General Register for Scotland records. Univariate associations between baseline variables and mortality were determined and multivariable survival analysis performed with Cox's proportional hazards modelling.

RESULTS

One hundred and fifty-eight (44.6%) of the 354 cohort members had died by the census date. Significantly more men (n = 102) died during follow-up than women (n = 56, chi2 = 5.27, p = .022). Lower scores on four of the six cognitive tests at age 76 years were associated with increased mortality, but not IQ age 11. Survival was associated with gender (H.R. 0.32, 95% C.I. 0.11-0.89 for women versus men), peak expiratory flow rate (H.R. 0.997, 95% C.I. 0.992-1.001 per l/min) and the Uses of Common Objects test (H.R. 0.91, 95% C.I. 0.82-1.01)

CONCLUSION

Both physical and psychological variables independently predicted survival in old age: respiratory function and executive function in particular. Male gender conferred increased risk of mortality and this was not explained by the broad range of socio-environmental, mental ability and health status variables examined in the study.

Ionizing radiation absorption of vascular surgeons during endovascular procedures

OBJECTIVE

Endovascular procedures have become an integral part of a vascular surgeon's practice. The exposure of surgeons to ionizing radiation and other safety issues have not been well studied. We investigated the radiation exposure of a team of vascular surgeons in an active endovascular unit and compared yearly dosages absorbed by various body parts among different surgeons. Patients' radiation exposure was also assessed.

METHODS

The radiation absorption of a team of vascular surgeons was prospectively monitored in a 12-month period. During each endovascular procedure, the effective body, eye, and hand radiation doses of all participating surgeons were measured by mini-thermoluminescent dosimeters (TLD) attached at the chest level under a lead apron, at the forehead at eye level, and at the hand. The type of procedure, fluoroscopy machine, fluoroscopy time, and personal and operating theatre radiation protection devices used in each procedure were also recorded. One TLD was attached to the patient's body near the operative site to measure the patient's dose. The yearly effective body, eye, and hand dose were compared with the safety limits of radiation for occupational exposure recommended by the International Commission on Radiation Protection (ICRP). The radiation absorption of various body parts per minute of fluoroscopy was compared among different surgeons.

RESULTS

A total of 149 consecutive endovascular procedures were performed, including 30 endovascular aortic repairs (EVAR), 58 arteriograms with and without embolization (AGM), and 61 percutaneous transluminal angioplasty and stent (PTA/S) procedures. The cumulative fluoroscopy time was 1132 minutes. The median yearly effective body, eye, and hand dose for the surgeons were 0.20 mSv (range, 0.13 to 0.27 mSv), 0.19 mSv (range, 0.10 to 0.33 mSv) and 0.99 mSv (0.29 to 1.84 mSv) respectively, which were well below the safety limits of the ICRP. The mean body, eye, and hand dose of the chief surgeon per procedure were highest for EVAR. A significant discrepancy was observed for the average hand dose per minute of fluoroscopy among different surgeons. The mean radiation absorption of patients who underwent EVAR, AGM, and PTA/S was 12.7 mSv, 13.6 mSv, and 3.4 mSv, respectively.

CONCLUSION

With current radiation protection practice, the radiation absorbed by vascular surgeons with a high endovascular workload did not exceed the safety limits recommended by ICRP. Variations in practice, however, can result in significant discrepancy of radiation absorption between surgeons.

Mortality from diseases other than cancer following low doses of ionizing radiation: results from the 15-Country Study of nuclear industry workers

BACKGROUND

Ionizing radiation at very high (radio-therapeutic) dose levels can cause diseases other than cancer, particularly heart diseases. There is increasing evidence that doses of the order of a few sievert (Sv) may also increase the risk of non-cancer diseases. It is not known, however, whether such effects also occur following the lower doses and dose rates of public health concern.

METHODS

We used data from an international (15-country) nuclear workers cohort study to evaluate whether mortality from diseases other than cancer is related to low doses of external ionizing radiation. Analyses included 275 312 workers with adequate information on socioeconomic status, over 4 million person-years of follow-up and an average cumulative radiation dose of 20.7 mSv; 11 255 workers had died of non-cancer diseases.

RESULTS

The excess relative risk (ERR) per Sv was 0.24 [95% CI (confidence intervals) -0.23, 0.78] for mortality from all non-cancer diseases and 0.09 (95% CI -0.43, 0.70) for circulatory diseases. Higher risk estimates were observed for mortality from respiratory and digestive diseases, but confidence intervals included zero. Increased risks were observed among the younger workers (attained age <50 years, identified post hoc) for all groupings of non-cancer causes of death, including external causes. It is unclear therefore whether these findings reflect real effects of radiation, random variation or residual confounding.

CONCLUSIONS

The most informative low-dose radiation study to date provides little evidence for a relationship between mortality from non-malignant diseases and radiation dose. However, we cannot rule out risks per unit dose of the same order of magnitude as found in studies at higher doses.