Assessing Nonlinearity in Harderian Gland Tumor Induction Using Three Combined HZE-irradiated Mouse Datasets.

Recently reported studies considering nonlinearity in the effects of low-dose space radiation have assumed a nontargeted mechanism. To date, few analyses have been performed to assess whether a nontargeted term is supported by the available data. The Harderian gland data from Alpen et al. (published in 1993 and 1994), and Chang et al. (2016) provide the most diversity of ions and energies in a tumor induction model, including multiple high-energy and charge particles. These data can be used to investigate various nonlinearity assumptions against a linear model, including nontargeted effects in the low-dose region or cell sterilization at high doses. In this work, generalized linear models were used with the log complement link function to analyze the binomial data from the studies independently and combined. While there was some evidence of nonlinearity that was best described by a cell-sterilization model, the linear model was adequate to describe the data. The current data do not support the addition of a nontargeted effects term in any model. While adequate data are available in the low-dose region (<0.5 Gy) to support a nontargeted effects term if valid, additional data in the 1-2 Gy region are necessary to achieve power for cell-sterilization analysis validation. The current analysis demonstrates that the Harderian gland tumor data do not support the use of a nontargeted effects term in human cancer risk models.

Radiation Exposure and Mortality from Cardiovascular Disease and Cancer in Early NASA Astronauts.

Understanding space radiation health effects is critical due to potential increased morbidity and mortality following spaceflight. We evaluated whether there is evidence for excess cardiovascular disease or cancer mortality in early NASA astronauts and if a correlation exists between space radiation exposure and mortality. Astronauts selected from 1959-1969 were included and followed until death or February 2017, with 39 of 73 individuals still alive at that time. Calculated standardized mortality rates for tested outcomes were significantly below U.S. white male population rates, including all-cardiovascular disease (n = 7, SMR = 33; 95% CI, 14-65) and all-cancer (n = 7, SMR = 43; 95% CI, 18-83), as anticipated in a healthy worker population. Space radiation doses for cohort members ranged from 0-78 mGy. No significant associations between space radiation dose and mortality were found using logistic regression with an internal reference group, adjusting for medical radiation. Statistical power of the logistic regression was <6%, remaining <12% even when expected risk level or observed deaths were assumed to be 10 times higher than currently reported. While no excess radiation-associated cardiovascular or cancer mortality risk was observed, findings must be tempered by the statistical limitations of this cohort; notwithstanding, this small unique cohort provides a foundation for assessment of astronaut health.

Solid Cancer Incidence among the Life Span Study of Atomic Bomb Survivors: 1958-2009.

This is the third analysis of solid cancer incidence among the Life Span Study (LSS) cohort of atomic bomb survivors in Hiroshima and Nagasaki, adding eleven years of follow-up data since the previously reported analysis. For this analysis, several changes and improvements were implemented, including updated dose estimates (DS02R1) and adjustment for smoking. Here, we focus on all solid cancers in aggregate. The eligible cohort included 105,444 subjects who were alive and had no known history of cancer at the start of follow-up. A total of 80,205 subjects had individual dose estimates and 25,239 were not in either city at the time of the bombings. The follow-up period was 1958-2009, providing 3,079,484 person-years of follow-up. Cases were identified by linkage with population-based Hiroshima and Nagasaki Cancer Registries. Poisson regression methods were used to elucidate the nature of the radiation-associated risks per Gy of weighted absorbed colon dose using both excess relative risk (ERR) and excess absolute risk (EAR) models adjusted for smoking. Risk estimates were reported for a person exposed at age 30 years with attained age of 70 years. In this study, 22,538 incident first primary solid cancer cases were identified, of which 992 were associated with radiation exposure. There were 5,918 cases (26%) that occurred in the 11 years (1999-2009) since the previously reported study. For females, the dose response was consistent with linearity with an estimated ERR of 0.64 per Gy (95% CI: 0.52 to 0.77). For males, significant upward curvature over the full dose range as well as restricted dose ranges was observed and therefore, a linear-quadratic model was used, which resulted in an ERR of 0.20 (95% CI: 0.12 to 0.28) at 1 Gy and an ERR of 0.010 (95% CI: -0.0003 to 0.021) at 0.1 Gy. The shape of the ERR dose response was significantly different among males and females (P = 0.02). While there was a significant decrease in the ERR with increasing attained age, this decrease was more rapid in males compared to females. The lowest dose range that showed a statistically significant dose response using the sex-averaged, linear ERR model was 0-100 mGy (P = 0.038). In conclusion, this analysis demonstrates that solid cancer risks remain elevated more than 60 years after exposure. Sex-averaged upward curvature was observed in the dose response independent of adjustment for smoking. Findings from the current analysis regarding the dose-response shape were not fully consistent with those previously reported, raising unresolved questions. At this time, uncertainties in the shape of the dose response preclude definitive conclusions to confidently guide radiation protection policies. Upcoming results from a series of analyses focusing on the radiation risks for specific organs or organ families, as well as continued follow-up are needed to fully understand the nature of radiation-related cancer risk and its public health significance. Data and analysis scripts are available for download at: http://www.rerf.or.jp .

Predictors of intrinsic motivation behind seatbelt use in a country where current use is low.

CONTEXT: Seatbelt use is a major determinant of a driver's safety on the road. In Turkey and other middle-income countries, seatbelt use is lower than in high-income countries and contributes to the higher burden of road traffic injuries. Assessing factors behind drivers' motivations to wear seatbelts can help determine appropriate interventions for specific subpopulations. OBJECTIVE: To analyze the factors predictive of whether drivers who wear seatbelts in Afyonkarahisar and Ankara, Turkey do so because they believe seatbelts can save their lives. METHODS: As part of the monitoring and evaluation of the Bloomberg Philanthropies Global Road Safety Programme, 817 drivers were randomly recruited in Afyonkarahisar and Ankara, Turkey, to participate in roadside interviews. Logistic regression was run on data from 408 drivers who claimed they always wore seatbelts. Predictors were driver's city, driver's age group (30 and younger, 31 to 40, and over 40 years), whether at least one passenger was in the car, and an interaction term between age group and whether passengers were in the car. The outcome variable of interest was whether drivers wore seatbelts because they believed seatbelts can save their lives, referred to in this paper as "selection of Reason 3." RESULTS: The odds of selecting Reason 3 were 2.45 (95% CI: 1.40-4.31) times higher in Ankara than in Afyonkarahisar, 2.52 (95% CI: 1.38-4.60) and 3.65 (95% CI: 1.92-6.95) times higher for drivers aged 31-40 and drivers over the age of 40 than for drivers 30 years of age and younger, respectively, and 5.89 (95% CI: 2.02-17.23), 7.22 (95% CI: 1.61-32.42), and 0.83 (95% CI: 0.32-2.19) times higher for drivers traveling with passengers who were 30 years of age and younger, between 31 and 40, and over 40 than for drivers traveling without passengers in these age groups, respectively. CONCLUSION: Drivers with passengers had higher odds of selecting Reason 3, especially younger drivers who are more likely to succumb to peer pressure. Older drivers had higher odds of selecting Reason 3. Peer groups and peer education campaigns may have an impact. Education interventions combined with extrinsic campaigns can be aimed at younger drivers to increase and maintain adherence in the population.