Naive CD4 T Cells Highly Expressing the Inflammatory Chemokine Receptor CXCR3 Increase with Age and Radiation Exposure in Atomic Bomb Survivors

The numbers of naive T cells that react to novel pathogens not yet encountered by an immune system, decrease during aging, mainly due to age-associated involution of the thymus. CD45RA+ naive CD4 T cells consist of heterogeneous populations, including highly CXCR3-expressing cells that appear during the homeostatic proliferation of naive T cells and exhibit enhanced type-1 inflammatory phenotypes. Based on previous evidence of radiation-associated reductions in thymic function and peripheral blood naive CD4 T cells, we hypothesized that the homeostatic proliferation of naive CD4 T cells compensates for deficits in peripheral T-cell populations after radiation injury, which may increase the proportion of CXCR3high cells in naive CD4 T cells and enhance inflammation. The statistical models employed in this study revealed positive associations between the number of CXCR3high naive CD4 T cells and age as well as radiation dose among 580 Hiroshima atomic bomb survivors. In addition, the CXCR3high cells in these survivors increased not only with the levels of homeostatic cytokines, IL6 and IL7, but also with those of inflammatory indicators, CXCL10 and CRP. These results suggest that thymic T-cell production deficiency due to radiation and aging results in enhanced homeostatic proliferation that drives the appearance of CXCR3high naive CD4 T cells poised for an inflammatory response. Molecular mechanisms and clinical relevance of increasing CXCR3high cells in naive CD4 T populations should be further investigated in the context of inflammatory disease development long after radiation exposure.

Neurocognitive Function in Aged Survivors Exposed to Atomic Bomb Radiation In Utero: The Radiation Effects Research Foundation Adult Health Study

Although some adverse effects on neurocognitive function have been reported in children and adolescents irradiated prenatally during the atomic bombings and the Chernobyl nuclear accident, little information is available for effects on the elderly. Here we evaluate the effects of prenatal exposure to atomic bomb radiation on subjective neurocognitive function in aged survivors. To evaluate neurocognitive impairment, we mailed the Neurocognitive Questionnaire (NCQ), a self-administered scale, to prenatally exposed survivors, including clinic visitors and non-visitors at the time of the 2011 and 2013 Adult Health Study (AHS) examinations. We received replies from 444 individuals (mean age, 66.9 ± 0.6 years). After adjusting for sex, city, and educational background, we found no significant effects of radiation, clinic visit, or interaction between radiation and clinic visit on the scores of the 4 NCQ factors of metacognition, emotional regulation, motivation/organization, and processing speed. Even in analyses considering gestational age at the time of the bombings, none of the 4 NCQ factor scores was related to maternal uterine dose. There remains the limitation that this study consisted of healthy survivors, but we found no significant radiation effect on late-life cognition in people prenatally exposed to atomic bomb radiation.

Risk Ratio and Risk Difference Estimation in Case-cohort Studies

BACKGROUND

In case-cohort studies with binary outcomes, ordinary logistic regression analyses have been widely used because of their computational simplicity. However, the resultant odds ratio estimates cannot be interpreted as relative risk measures unless the event rate is low. The risk ratio and risk difference are more favorable outcome measures that are directly interpreted as effect measures without the rare disease assumption.

METHODS

We provide pseudo-Poisson and pseudo-normal linear regression methods for estimating risk ratios and risk differences in analyses of case-cohort studies. These multivariate regression models are fitted by weighting the inverses of sampling probabilities. Also, the precisions of the risk ratio and risk difference estimators can be improved using auxiliary variable information, specifically by adapting the calibrated or estimated weights, which are readily measured on all samples from the whole cohort. Finally, we provide computational code in R (R Foundation for Statistical Computing, Vienna, Austria) that can easily perform these methods.

RESULTS

Through numerical analyses of artificially simulated data and the National Wilms Tumor Study data, accurate risk ratio and risk difference estimates were obtained using the pseudo-Poisson and pseudo-normal linear regression methods. Also, using the auxiliary variable information from the whole cohort, precisions of these estimators were markedly improved.

CONCLUSION

The ordinary logistic regression analyses may provide uninterpretable effect measure estimates, and the risk ratio and risk difference estimation methods are effective alternative approaches for case-cohort studies. These methods are especially recommended under situations in which the event rate is not low.

Female "Paradox" in Atrial Fibrillation-Role of Left Truncation Due to Competing Risks

Female sex in patients with atrial fibrillation (AF) is a controversial and paradoxical risk factor for stroke-controversial because it increases the risk of stroke only among older women of some ethnicities and paradoxical because it appears to contradict male predominance in cardiovascular diseases. However, the underlying mechanism remains unclear. We conducted simulations to examine the hypothesis that this sex difference is generated non-causally through left truncation due to competing risks (CR) such as coronary artery diseases, which occur more frequently among men than among women and share common unobserved causes with stroke. We modeled the hazards of stroke and CR with correlated heterogeneous risk. We assumed that some people died of CR before AF diagnosis and calculated the hazard ratio of female sex in the left-truncated AF population. In this situation, female sex became a risk factor for stroke in the absence of causal roles. The hazard ratio was attenuated in young populations without left truncation and in populations with low CR and high stroke incidence, which is consistent with real-world observations. This study demonstrated that spurious risk factors can be identified through left truncation due to correlated CR. Female sex in patients with AF may be a paradoxical risk factor for stroke.

Chromosome aberrations among atomic-bomb survivors exposed in utero: updated analysis accounting for revised radiation doses and smoking

A previous study of peripheral blood lymphocyte translocations around age 40 among atomic-bomb survivors exposed in utero revealed no overall association with radiation dose-despite a clear association between translocations and dose among their mothers-but the data suggested an increase at doses below 100 mGy with a definite peak. That analysis of the in utero-exposed survivors did not adjust for their subsequent smoking behavior, an established cause of chromosomal aberrations, or their subsequent exposures to medical irradiation, a potential mediator. In addition, atomic-bomb survivor radiation dose estimates have subsequently been updated and refined. We therefore re-estimated the dose response using the latest DS02R1 dose estimates and adjusting for smoking as well as for city and proximal-distal location at the time of exposure to the atomic bomb. Sex of the survivor, mother's age around the time of conception, and approximate trimester of gestation at the time of exposure were also considered as explanatory variables and modifiers. Precision of the estimated dose response was slightly lower due to greater variability near zero in the updated dose estimates, but there was little change in evidence of a low-dose increase and still no suggestion of an overall increase across the entire dose range. Adjustment for smoking behavior led to a decline in background number of translocations (the dose-response intercept), but smoking did not interact with dose overall (across the entire dose range). Adjustment for medical irradiation did not alter the association between dose and translocation frequency. Sex, mother's age, and trimester were not associated with number of translocations, nor did they interact with dose overall. Interactions with dose in the low-dose range could not be evaluated because of numerical instability.

Radiation Effects on Late-life Neurocognitive Function in Childhood Atomic Bomb Survivors: A Radiation Effects Research Foundation Adult Health Study

High-dose radiation in childhood such as is used in radiation therapy causes cognitive decline, but there is insufficient research on the cognitive effects of low- to medium-dose radiation. We aimed to reveal the association between atomic bomb radiation exposure in childhood and late-life neurocognitive function. In 2011 and 2013, we mailed the Neurocognitive Questionnaire (NCQ) to subjects who were 12 years old or younger at the time of the atomic bombing. We converted the four NCQ subscales (metacognition, emotional regulation, motivation/organization, and processing speed) to T scores and defined the highest 10% of the controls (exposure dose < 5 mGy) as impaired. We used a generalized linear mixed model to evaluate the effect of radiation exposure on T scores and percentage impaired. We enrolled 859 participants. At the time of the bombing, the mean (SD) age was 6.7 (3.8) years for the control (N = 390) and 6.1 (3.8) years for the exposed (N = 469). At the time of replying to the questionnaire, the mean age of all the participants was 73.7 (3.8) years of age. After adjusting for cofactors, older age was related to the decline of all neurocognitive subscales. Sex and education level had relevance to some of the subscales. For neurocognitive function, exposure dose was not related except to percentage impaired, motivation/organization. Late-life neurocognitive function in atomic bomb survivors exposed as children was associated with age, but not clearly with radiation dose. More studies are needed to evaluate the effect of low-dose radiation during childhood on long-term neurocognitive function.

Radiation effects on atherosclerosis in atomic bomb survivors: a cross-sectional study using structural equation modeling

Past reports indicated that total-body irradiation at low to moderate doses could be responsible for cardiovascular disease risks, but the mechanism remains unclear. The purpose of this study was to investigate the association between radiation exposure and atherosclerosis, an underlying pathology of cardiovascular diseases, in the Japanese atomic bomb survivors. We performed a cross-sectional study measuring 14 clinical-physiological atherosclerosis indicators during clinical exams from 2010 to 2014 in 3274 participants of the Adult Health Study cohort. Multivariable analyses were performed by using a structural equation model with latent factors representing underlying atherosclerotic pathologies: (1) arterial stiffness, (2) calcification, and (3) plaque　as measured with indicators chosen a priori on the basis of clinical-physiological knowledge. Radiation was linearly associated with calcification (standardized coefficient per Gy 0.15, 95 % confidence interval: CI [0.070, 0.23]) and plaque (0.11, 95 % CI [0.029, 0.20]), small associations that were comparable to about 2 years of aging per Gy of radiation exposure, but not with arterial stiffness (0.036, 95 % CI [− 0.025, 0.095]). The model fitted better and had narrower confidence intervals than separate ordinary regression models explaining individual indicators independently. The associations were less evident when the dose range was restricted to a maximum of 2 or 1 Gy. By combining individual clinical-physiological indicators that are correlated because of common, underlying atherosclerotic pathologies, we found a small, but significant association of radiation with atherosclerosis.

Mortality among individuals exposed to atomic bomb radiation in utero: 1950-2012

We examined the mortality risks among 2463 individuals who were exposed in utero to atomic bomb radiation in Hiroshima or Nagasaki in August 1945 and were followed from October 1950 through 2012. Individual estimates of mother's weighted absorbed uterine dose (DS02R1) were used. Poisson regression method was used to estimate the radiation-associated excess relative risk per Gy (ERR/Gy) and 95% confidence intervals (CI) for cause-specific mortality. Head size, birth weight, and parents' survival status were evaluated as potential mediators of radiation effect. There were 339 deaths (216 males and 123 females) including deaths from solid cancer (n = 137), lymphohematopoietic cancer (n = 8), noncancer disease (n = 134), external cause (n = 56), and unknown cause (n = 4). Among males, the unadjusted ERR/Gy (95% CI) was increased for noncancer disease mortality (1.22, 0.10-3.14), but not for solid cancer mortality (- 0.18, < - 0.77-0.95); the unadjusted ERR/Gy for external cause mortality was not statistically significant (0.28, < - 0.60-2.36). Among females, the unadjusted ERRs/Gy were increased for solid cancer (2.24, 0.44-5.58), noncancer (2.86, 0.56-7.64), and external cause mortality (2.57, 0.20-9.19). The ERRs/Gy adjusted for potential mediators did not change appreciably for solid cancer mortality, but decreased notably for noncancer mortality (0.39, < - 0.43-1.91 for males; 1.48, - 0.046-4.55 for females) and external cause mortality (0.10, < - 0.57-1.96 for males; 1.38, < - 0.46-5.95 for females). In conclusion, antenatal radiation exposure is a consistent risk factor for increased solid cancer mortality among females, but not among males. The effect of exposure to atomic bomb radiation on noncancer disease and external cause mortality among individuals exposed in utero was mediated through small head size, low birth weight, and parental loss.

Longitudinal changes in red blood cell distribution width decades after radiation exposure in atomic-bomb survivors

Red blood cell distribution width (RDW), which generally increases with age, is a risk marker for morbidity and mortality in various diseases. We investigated the association between elevated RDW and prior radiation exposure by examining longitudinal RDW changes in 4204 atomic‐bomb survivors over 15 years. A positive association was found between RDW and radiation dose, wherein RDW increased by 0·18%/Gy. This radiation‐associated effect increased as the participants aged. Elevated RDW was also associated with higher all‐cause mortality. The biological mechanisms underlying these observed associations merit further investigation.

Lifetime Mortality Risk from Cancer and Circulatory Disease Predicted from the Japanese Atomic Bomb Survivor Life Span Study Data Taking Account of Dose Measurement Error

Dosimetric measurement error is known to potentially bias the magnitude of the dose response, and can also affect the shape of dose response. In this report, generalized relative and absolute rate models are fitted to the latest Japanese atomic bomb survivor solid cancer, leukemia and circulatory disease mortality data (followed from 1950 through 2003), with the latest (DS02R1) dosimetry, using Bayesian techniques to adjust for errors in dose estimates and assessing other model uncertainties. Linear-quadratic models are fitted and used to assess lifetime mortality risks for contemporary UK, USA, French, Russian, Japanese and Chinese populations. For a test dose of 0.1 Gy absorbed dose weighted by neutron relative biological effectiveness, solid cancer, leukemia and circulatory disease mortality risks for a UK population using a generalized linear-quadratic relative rate model were estimated to be 3.88% Gy-1 [95% Bayesian credible interval (BCI): 1.17, 6.97], 0.35% Gy-1 (95% BCI: -0.03, 0.78) and 2.24% Gy-1 (95% BCI: -0.17, 13.76), respectively. Using a generalized absolute rate linear-quadratic model at 0.1 Gy, the lifetime risks for these three end points were estimated to be 3.56% Gy-1 (95% BCI: 0.54, 6.78), 0.41% Gy-1 (95% BCI: 0.01, 0.86) and 1.56% Gy-1 (95% BCI: -1.10, 7.21), respectively. There was substantial evidence of curvature for solid cancer (in particular, the group of solid cancers excluding lung, breast and stomach cancers) and leukemia, so that for solid cancer and leukemia, estimates of excess risk per unit dose were nearly doubled by increasing the dose from 0.01 to 1.0 Gy, with most of the increase occurring in the interval from 0.1 to 1.0 Gy. For circulatory disease, the dose-response curvature was inverse, so that risk per unit dose was nearly halved by going from 0.01 t o 1.0 Gy weighted absorbed dose, although there were substantial uncertainties. In general, there were higher radiation risks for females compared to males. This was true for solid cancer and circulatory disease overall, as well as for lung, breast, stomach and the group of other solid cancers, and was the case whether relative or absolute rate projection models were employed; however, for leukemia this pattern was reversed. Risk estimates varied somewhat between populations, with lower cancer risks in aggregate for China and Russia, but higher circulatory disease risks for Russia, particularly using the relative rate model. There was more pronounced variation for certain cancer sites and certain types of projection models, so that breast cancer risk was markedly lower in China and Japan using a relative rate model, but the opposite was the case for stomach cancer. There was less variation between countries using the absolute rate models for stomach cancer and breast cancer, but this was not the case for lung cancer and the group of other solid cancers, or for circulatory disease.

Effects of Radiation on Blood Pressure and Body Weight in the Spontaneously Hypertensive Rat Model. Are Radiation Effects on Blood Pressure Affected by Genetic Background?

In this work, we utilized spontaneously hypertensive rats (SHR) and Wister Kyoto rats (WKY), from which the SHR was established, to evaluate the effects of whole-body acute radiation on the cardiovascular system at doses from 0 to 4 Gy. In the irradiated SHR, the systolic blood pressure (SBP) increased with increasing dose, while body weight gain decreased with increasing radiation dose. Furthermore, pathological observations of SHR demonstrated that the number of rats with cystic degeneration in the liver increased with increasing dose. The effects observed among SHR, such as increased SBP and retardation of body weight gain, appear very similar to those observed in Japanese atomic bomb survivors. In contrast, the SBP among WKY did not change relative to dose; the body weight, however, did change, as in the SHR. Therefore, the association between radiation exposure and SBP, but not between radiation exposure and retardation of body weight gain, may be affected by genetic background, as evident from strain difference. These results suggest that the SHR and WKY animal models may be useful for studying radiation effects on non-cancer diseases including circulatory diseases, chronic liver disease and developmental retardation.

Association between low doses of ionizing radiation, administered acutely or chronically, and time to onset of stroke in a rat model

Exposure to high-doses of ionizing radiation has been reported to be associated with the risk of stroke. However, risks associated with lower dose exposures remain unclear, and there is little information available for the risk modification according to the dose-rate. There are few studies using animal models which might be able to provide complementary information on this association. In this study, the male stroke-prone spontaneously hypertensive rat (SHRSP) was used as a model animal. The rats were acutely irradiated with doses between 0 and 1.0 Gy or chronically irradiated with a cumulative dose of 0.5 or 1.0 Gy (at a dose rate of 0.05 or 0.1 Gy/day, respectively). The onset time of stroke related symptoms in SHRSP was used as an endpoint for evaluating the effects of low dose and the low dose-rate gamma-ray exposures. With respect to acute exposure, the time to the onset of stroke in the irradiated rats suggested the presence of a threshold around 0.1 Gy. For the low dose-rate chronically exposed, no significant increase in stroke symptom was observed. These findings are novel and demonstrate that the SHRSP system can be used to determine the association between the risk of stroke and radiation exposure with high sensitivity. Moreover, these studies provide important information regarding the association between the low dose and low dose-rate radiation exposure and circulatory diseases, especially stroke.

Increased cancer mortality among Japanese individuals with hyperinsulinemia

AIMS

To evaluate the effect of hyperinsulinemia on cancer death, we clarified the association between hyperinsulinemia and cancer mortality among Japanese individuals.

METHODS

All the participants (5586 men and 6652 women) lived in Hiroshima City, underwent a 75 g oral glucose tolerance test between 1994 and 2012, and were followed for mortality until August 2013. A systematic review of death certificates was used to confirm the cause of death.

RESULTS

During the follow-up period (median, 10.0 years), 587 participants died of cancer. Lung cancer was the most common cause of organ-specific death. We divided the participants into 3 groups according to the tertiles of fasting immunoreactive insulin (FIRI) levels (low, middle, and high groups). The high group had the highest mortality rate (5.5 per 1000 person-years). The hazard ratio (HR) for cancer mortality of the high group after adjustment for possible confounders, such as age, sex, body mass index, smoking status, alcohol intake, and radiation effects (model 1), was significantly higher than that of the low group (HR, 1.55; 95% confidence interval (CI), 1.23-1.95). In model 2 (model 1 plus fasting plasma glucose) and model 3 (model 1 plus HbA1c), the multivariate HRs for cancer mortality were 1.46 (95% CI, 1.15-1.85) and 1.48 (95% CI, 1.17-1.87), respectively.The HR for cancer death at high FIRI levels (per 1 μU/mL) was 1.04 (95% CI, 1.02-1.05) in all participants after adjusting for fasting plasma glucose level and other confounders. In the subgroup analysis, the HRs were 1.03 (95% CI, 0.98-1.09), 1.05 (95% CI, 1.02-1.08), and 1.04 (95% CI, 1.02-1.06) in the normal, prediabetes, and diabetes group, respectively.

CONCLUSIONS

Hyperinsulinemia was associated with a high risk of cancer mortality and may be an important link between cancer mortality and diabetes or prediabetes.

Association between a biomarker of glucose spikes, 1,5-anhydroglucitol, and cancer mortality

INTRODUCTION

1,5-Anhydroglucitol (1,5-AG) is a biomarker of glucose spikes. To evaluate the effect of acute glucose excursions on cancer death, we clarified the association between 1,5-AG and cancer mortality among Japanese individuals with normal glucose tolerance.

RESEARCH DESIGN AND METHODS

We measured 1,5-AG in 6783 (2842 men, 3941 women) individuals with normal fasting and 2-hour plasma glucose who received a 75 g oral glucose tolerance test between 1994 and 2012. They were followed for mortality until August 2013. A systematic review of death certificates was used to confirm the cause of death. We divided the participants into four groups according to the quartile of 1,5-AG level at registration. We used Cox regression to clarify the association between 1,5-AG levels and cancer mortality with multivariate adjustment for possible confounders.

RESULTS

During the follow-up period (median, 10.0 years), 140 men and 109 women died of cancer. The HR for cancer mortality of the lowest quartile group was higher than that of the highest quartile group in men (HR, 2.62; 95% CI, 1.60 to 4.41) and in women (HR, 1.47; 95% CI, 0.88 to 2.47). These associations were not attenuated with further adjustment for HbA1c.

CONCLUSIONS

1,5-AG was associated with high risk of cancer mortality in Japanese men after adjustment for HbA1c.

Biologically-based modeling of radiation risk and biomarker prevalence for papillary thyroid cancer in Japanese a-bomb survivors 1958-2005

PURPOSE

Thyroid cancer of papillary histology (PTC) is the dominant type in radio-epidemiological cohorts established after nuclear accidents or warfare. Studies on post-Chernobyl PTC and on thyroid cancer in the life span study (LSS) of Japanese a-bomb survivors consistently revealed high radiation risk after exposure during childhood and adolescence. For post-Chernobyl risk assessment overexpression of the CLIP2 gene was proposed as molecular biomarker to separate radiogenic from sporadic PTC. Based on such binary marker a biologically-based risk model of PTC carcinogenesis has been developed for observational Chernobyl data. The model featured two independent molecular pathways of disease development, of which one was associated with radiation exposure. To gain credibility the concept for a mechanistic risk model must be based on general biological features which transcend findings in a single cohort. The purpose of the present study is therefore to demonstrate portability of the model concept by application to PTC incidence data in the LSS. By exploiting the molecular two-path concept we improve the determination of the probability of radiation causing cancer (POC).

MATERIALS AND METHODS

The current analysis uses thyroid cancer incidence data of the LSS with thyroid cancer diagnoses and papillary histology (n = 292) from the follow-up period between 1958 and 2005. Risk analysis was performed with both descriptive and biologically-based models.

RESULTS

Judged by goodness-of-fit all applied models described the data almost equally well. They yielded similar risk estimates in cohorts post-Chernobyl and LSS. The preferred mechanistic model was selected by biological plausibility. It reflected important features of an imperfect radiation marker which are not easily addressed by descriptive models. Precise model predictions of marker prevalence in strata of epidemiological covariables can be tested by molecular measurements. Application of the radiation-related molecular pathway from our preferred model in retrospective risk assessment decreases the threshold dose for 50% POC from 0.33 (95% confidence interval (CI) 0.18; 0.64) Gy to 0.04 (95% CI 0.01; 0.19) Gy for females and from 0.43 (95% CI 0.17; 1.84) Gy to 0.19 (95% CI 0.05; 1.00) Gy for males. These improvements are still not sufficient to separate radiation-induced from sporadic PTC cases at very low doses <0.015 Gy typical for the Fukushima accident.

CONCLUSIONS

Successful application of our preferred mechanistic model to LSS incidence data confirms and improves the biological two-path concept of radiation-induced PTC. Model predictions suggest further molecular validation studies to consolidate the basis of biologically-based risk estimation.

Longitudinal examination of pancreatic β-cell function in Japanese individuals

AIMS/INTRODUCTION

We carried out a retrospective, longitudinal analysis of β-cell function between a diabetes mellitus group, including those that progressed to diabetes mellitus during the follow-up period, and a diabetic type with glycated hemoglobin (HbA1c) <6.5 group, including those that progressed to a diabetic type during the follow-up period. β-Cell function was assessed using homeostasis model of assessment of β-cell function.

MATERIALS AND METHODS

The relationship between the duration of diabetes mellitus or the diabetic type and pancreatic β-cell function was compared between the diabetes mellitus group (1,817) and diabetic type with HbA1c <6.5 group (1,843) using results from an oral glucose tolerance test. Linear mixed effects models were used to analyze repeated measurements of oral glucose tolerance tests.

RESULTS

The slope of the regression line of β-cell function for the duration of the diabetes mellitus group was -2.2%/year before the diagnosis. The slope differed after the diagnosis, and the difference was 1.3. The slope of the diabetic type group was -1.2%/year, and no significant difference was observed in the slope before and after the diagnosis. β-Cell function at the onset was 54.3% in the diabetic type group and 40.6% in the diabetes mellitus group, and the slope of the regression line was significantly higher in the diabetes mellitus group. We divided the diabetes mellitus and diabetic type with HbA1c <6.5 groups into obese and non-obese participants. β-Cell function declined more with obesity.

CONCLUSIONS

Subsequent declines in β-cell function were faster in the diabetes mellitus group than that in the diabetic type with HbA1c <6.5 group, and increased with obesity.

Association Between Prevalence of Peripheral Artery Disease and Radiation Exposure in the Atomic Bomb Survivors

Background

Past reports suggested that total‐body irradiation at 0.5 to 1.0 Gy could be responsible for atherosclerosis. Peripheral artery disease (PAD) is a manifestation of systematic atherosclerosis. Whether the consequences of a low‐to‐moderate dose of radiation include increased risk of PAD remains to be determined. The purpose of this study was to examine the association between radiation exposure and prevalence of PAD among Japanese atomic bomb survivors.

Methods and Results

Radiation exposure from the atomic bombing was assessed in 3476 participants (41.1% men, mean age 74.8 years with SD 6.4 years) with a cross‐sectional survey in 2010 to 2014. Left‐ and right‐side ankle‐brachial indexes and upstroke time (UT) were obtained using oscillometric VP‐2000. PAD was defined as an ankle‐brachial index of 1.0 or less or a prior history related to revascularization. UT was considered a sensitive marker of early‐stage PAD. Association between radiation exposure and PAD or UT was assessed using multivariable regression analyses with adjustment for potential confounding factors. Of 3476 participants, 79 (2.3%) were identified as having prevalent PAD. Multivariate logistic regression analysis indicated that radiation dose was unrelated to PAD prevalence (odds ratio, 0.83; 95% confidence interval [0.57‐1.21]). UT appeared to increase with radiation dose, but the increase was not statistically significant (1.09 ms/Gy; 95% confidence interval [−0.17 to 2.36]).

Conclusions

We found no clear association of radiation dose with PAD, but it remains to be determined whether UT is associated with radiation dose.

Radiation risk of incident colorectal cancer by anatomical site among atomic bomb survivors: 1958-2009

Radiation effects on colorectal cancer rates, adjusted for smoking, alcohol intake and frequency of meat consumption and body mass index (BMI) by anatomical subsite (proximal colon, distal colon and rectum) were examined in a cohort of 105,444 atomic bomb survivors. Poisson regression methods were used to describe radiation‐associated excess relative risks (ERR) and excess absolute rates (EAR) for the 1958–2009 period. There were 2,960 first primary colorectal cancers including 894 proximal, 871 distal and 1,046 rectal cancers. Smoking, alcohol intake and BMI were associated with subsite‐specific cancer background rates. Significant linear dose–responses were found for total colon (sex‐averaged ERR/Gy for 70 years old exposed at age 30 = 0.63, 95% confidence interval [CI]: 0.34; 0.98), proximal [ERR = 0.80, 95% CI: 0.32; 1.44] and distal colon cancers [ERR = 0.50, 95% CI: 0.04; 0.97], but not for rectal cancer [ERR = 0.023, 95% CI: −0.081; 0.13]. The ERRs for proximal and distal colon cancers were not significantly different (p = 0.41). The ERR decreased with attained age for total colon, but not for proximal colon cancer, and with calendar year for distal colon cancer. The ERRs and EARs did not vary by age at exposure, except for decreasing trend in EAR for proximal colon cancer. In conclusion, ionizing radiation is associated with increased risk of proximal and distal colon cancers. The ERR for proximal cancer persists over time, but that for distal colon cancer decreases. There continues to be no indication of radiation effects on rectal cancer incidence in this population.

What's new?

Increasing radiation dose is associated with elevated colon cancer incidence among atomic bomb survivors. Questions remain, however, about differences in radiation‐related increases in risk by anatomical subsite, particularly the proximal and distal colon and the rectum. In this study, analyses of radiation and colorectal cancer risk for Japanese atomic bomb survivors in the Life Span Study cohort show that ionizing radiation is associated specifically with elevated risk of proximal and distal colon cancers. Adjustment for body mass index and lifestyle factors had little effect on radiation risk estimates. No association was found between radiation exposure and rectal cancer.

Association of Weight Fluctuation With Mortality in Japanese Adults

IMPORTANCE

Weight cycling is associated with the risk of mortality from heart disease, but many studies have not distinguished between simple nonlinear (monotone) weight changes and more complex changes that reflect fluctuations.

OBJECTIVE

To assess whether extreme body weight variation is associated with mortality after controlling for nonlinear weight changes.

DESIGN, SETTING, AND PARTICIPANTS

In this prospective clinical cohort study, 4796 Japanese atomic bomb survivors were examined in the clinic as part of a biennial health examination and research program. The study consisted of a 20-year longitudinal baseline period (July 1, 1958, to June 30, 1978) and subsequent mortality follow-up of 27 years (July 1, 1978, to June 30, 2005) Participants were initially between the ages of 20 and 49 years during the baseline period and, throughout the baseline period, had no diagnoses of cardiovascular disease (CVD) or cancer and attended at least 7 of 10 scheduled examinations. Data analysis was performed from October 16, 2015, to May 13, 2016.

EXPOSURES

Residual variability in body mass index (BMI) during the baseline period.

MAIN OUTCOMES AND MEASURES

Outcomes were mortality from ischemic heart disease, cerebrovascular disease, other CVDs combined, other causes (except cancer), and cancer. Root mean squared error was calculated to capture individual residual variation in BMI after adjustment for baseline BMI trends, and the association of magnitude of residual variation with mortality was calculated as relative risk.

RESULTS

In total, 4796 persons (mean [SD] age, 35.0 [7.3] years at first baseline examination; 3252 [67.8%] female; mean [SD] BMI, 21.2 [2.8] at first baseline visit [20.6 (2.4) among men and 21.5 (2.9) among women]) participated in the study. During follow-up, 1550 participants died: 82 (5.3% of all deaths) of ischemic heart disease, 181 (11.7%) of cerebrovascular disease, 186 (12.0%) of other CVDs, 615 (39.7%) of cancer, and 486 (31.3%) of other causes. Magnitude of residual variation in weight was associated with all-cause mortality (relative risk, 1.25 for 1 U of additional variation; 95% CI, 1.06-1.47) and ischemic heart disease mortality (relative risk, 2.49; 95% CI, 1.41-4.38).

CONCLUSIONS AND RELEVANCE

The findings suggest that an association exists between weight variation and heart disease mortality and that weight loss interventions, if deemed to be necessary, should be considered carefully.

Stepwise approach to SNP-set analysis illustrated with the Metabochip and colorectal cancer in Japanese Americans of the Multiethnic Cohort

BACKGROUND

Common variants have explained less than the amount of heritability expected for complex diseases, which has led to interest in less-common variants and more powerful approaches to the analysis of whole-genome scans. Because of low frequency (low statistical power), less-common variants are best analyzed using SNP-set methods such as gene-set or pathway-based analyses. However, there is as yet no clear consensus regarding how to focus in on potential risk variants following set-based analyses. We used a stepwise, telescoping approach to analyze common- and rare-variant data from the Illumina Metabochip array to assess genomic association with colorectal cancer (CRC) in the Japanese sub-population of the Multiethnic Cohort (676 cases, 7180 controls). We started with pathway analysis of SNPs that are in genes and pathways having known mechanistic roles in colorectal cancer, then focused on genes within the pathways that evidenced association with CRC, and finally assessed individual SNPs within the genes that evidenced association. Pathway SNPs downloaded from the dbSNP database were cross-matched with Metabochip SNPs and analyzed using the logistic kernel machine regression approach (logistic SNP-set kernel-machine association test, or sequence kernel association test; SKAT) and related methods.

RESULTS

The TGF-β and WNT pathways were associated with all CRC, and the WNT pathway was associated with colon cancer. Individual genes demonstrating the strongest associations were TGFBR2 in the TGF-β pathway and SMAD7 (which is involved in both the TGF-β and WNT pathways). As partial validation of our approach, a known CRC risk variant in SMAD7 (in both the TGF-β and WNT pathways: rs11874392) was associated with CRC risk in our data. We also detected two novel candidate CRC risk variants (rs13075948 and rs17025857) in TGFBR2, a gene known to be associated with CRC risk.

CONCLUSIONS

A stepwise, telescoping approach identified some potentially novel risk variants associated with colorectal cancer, so it may be a useful method for following up on results of set-based SNP analyses. Further work is required to assess the statistical characteristics of the approach, and additional applications should aid in better clarifying its utility.

A semiparametric approach to evaluate the harm of low-dose exposures

While moderate to high levels of radiation exposure is known to cause adverse health effects, there is still controversy about the lowest dose that could be harmful. Given that epidemiological studies of practical sizes are unlikely to provide sufficient statistical power to detect a small risk in the low-dose range of concern, greater emphasis should be given to evaluating low-dose risk uncertainty. Using simulations under various dose-response relationships with a threshold, we show that a conventional approach based on simple parametric models (e.g. the linear model with or without a threshold) can be inefficient, biased and/or inaccurate in uncertainty evaluations at low doses. Alternatively, we consider a Bayesian semiparametric model of a connected piecewise-linear function allowing for autocorrelations between adjacent line sections. With no specific assumption, this can describe various plausible dose-response curves while appropriately handling the risk uncertainty. In particular, it can relatively accurately evaluate the dose range in which a threshold might exist, while retaining statistical power for a small risk increase after the threshold. As an illustration, we analyse cancer incidence data of Japanese atomic bomb survivors, a primary epidemiological source of quantitative risk estimates for health effects from radiation exposure.

Body composition and development of diabetes: a 15-year follow-up study in a Japanese population

BACKGROUND/OBJECTIVES

Few longitudinal studies have examined the association between diabetes risk and body composition in Asians. The aim of this prospective cohort study was to determine the role of body composition, estimated by whole-body dual-energy X-ray absorptiometry, in the development of diabetes and to examine the impact of body composition on diabetes risk in normal weight (body mass index (BMI) <23 kg/m²) and overweight/obese groups (≥23 kg/m²).

SUBJECTS/METHODS

We measured the body composition for 1532 diabetes-free subjects (463 men and 1069 women), aged 48-79 years, at the baseline examination period from 1994-96 and followed-up to detect new cases of diabetes over the next 15 years (median 13.4 years).

RESULTS

After being adjusted for BMI and other potential confounding factors, body fat distribution was associated with diabetes risk. Percentage of trunk fat was positively associated with the development of diabetes (hazards ratio (HR) per 1 SD (95% confidential interval (CI)), 1.58 (1.10-2.28) in men, and 1.34 (0.99-1.83) in women), and percentage of leg fat was negatively associated with the development of diabetes (HR per 1 SD (95% CI), 0.68 (0.50-0.91) in men and 0.68 (0.55-0.85) in women). The estimated HRs of % trunk and leg fat on the development of diabetes differed little between normal weight and overweight/obese subjects. Appendicular lean mass was also negatively associated with diabetes risk only in normal weight men.

CONCLUSIONS

Opposite associations of trunk fat and leg fat with diabetes risk were observed. Assessment of body composition might help in the evaluation of diabetes risk.

Radiation- and Age-Associated Changes in Peripheral Blood Dendritic Cell Populations among Aging Atomic Bomb Survivors in Japan

Previous immunological studies in atomic bomb survivors have suggested that radiation exposure leads to long-lasting changes, similar to immunological aging observed in T-cell-adaptive immunity. However, to our knowledge, late effects of radiation on dendritic cells (DCs), the key coordinators for activation and differentiation of T cells, have not yet been investigated in humans. In the current study, we hypothesized that numerical and functional decreases would be observed in relationship to radiation dose in circulating conventional DCs (cDCs) and plasmacytoid DCs (pDCs) among 229 Japanese A-bomb survivors. Overall, the evidence did not support this hypothesis, with no overall changes in DCs or functional changes observed with radiation dose. Multivariable regression analysis for radiation dose, age and gender effects revealed that total DC counts as well as subpopulation counts decreased in relationship to increasing age. Further analyses revealed that in women, absolute numbers of pDCs showed significant decreases with radiation dose. A hierarchical clustering analysis of gene expression profiles in DCs after Toll-like receptor stimulation in vitro identified two clusters of participants that differed in age-associated expression levels of genes involved in antigen presentation and cytokine/chemokine production in cDCs. These results suggest that DC counts decrease and expression levels of gene clusters change with age. More than 60 years after radiation exposure, we also observed changes in pDC counts associated with radiation, but only among women.

Radiation- and Age-Associated Changes in Peripheral Blood Dendritic Cell Populations among Aging Atomic Bomb Survivors in Japan

Previous immunological studies in atomic bomb survivors have suggested that radiation exposure leads to long-lasting changes, similar to immunological aging observed in T-cell-adaptive immunity. However, to our knowledge, late effects of radiation on dendritic cells (DCs), the key coordinators for activation and differentiation of T cells, have not yet been investigated in humans. In the current study, we hypothesized that numerical and functional decreases would be observed in relationship to radiation dose in circulating conventional DCs (cDCs) and plasmacytoid DCs (pDCs) among 229 Japanese A-bomb survivors. Overall, the evidence did not support this hypothesis, with no overall changes in DCs or functional changes observed with radiation dose. Multivariable regression analysis for radiation dose, age and gender effects revealed that total DC counts as well as subpopulation counts decreased in relationship to increasing age. Further analyses revealed that in women, absolute numbers of pDCs showed significant decreases with radiation dose. A hierarchical clustering analysis of gene expression profiles in DCs after Toll-like receptor stimulation in vitro identified two clusters of participants that differed in age-associated expression levels of genes involved in antigen presentation and cytokine/chemokine production in cDCs. These results suggest that DC counts decrease and expression levels of gene clusters change with age. More than 60 years after radiation exposure, we also observed changes in pDC counts associated with radiation, but only among women.

Aging-related changes in human T-cell repertoire over 20years delineated by deep sequencing of peripheral T-cell receptors

Recent deep sequencing studies on T-cell receptor (TCR) repertoire have provided robust data to characterize diversity of T-cell immune responsiveness to a wide variety of peptide antigens, including viral and tumor antigens. The human TCR repertoire declines with age, but this decline has not been fully investigated longitudinally in individuals. Using a deep sequencing approach, we analyzed TCRβ repertoires longitudinally over approximately 20years, with ages ranging from 23 to 50years at the start (23 to 65years overall), in peripheral-blood CD4 and CD8 T-cell populations that were collected and cryopreserved 3 times at intervals of approximately 10years from each of 6 healthy adults (3 men and 3 women). Sequence data at the hypervariable complementarity determining region 3 (CDR3) in the TCRB gene locus were evaluated by applying a random-coefficient statistical regression model. Two outcomes were analyzed: total number of distinct TCRB CDR3 sequences as a TCR diversity metric, and clonality of the T-cell populations. TCR repertoire diversity decreased (p<0.001) and frequencies of clonal populations increased (p=0.003) with age in CD8 T cells, whereas CD4 T cells retained fairly diverse TCR repertoires along with relatively low clonality. We also found that approximately 10-30% and 30-80% of read sequences in CD4 and CD8 T cells, respectively, overlapped at different ages within each individual, indicating long-term stable maintenance of T-cell clonal composition. Moreover, many of the most frequent TCRB CDR3 sequences (i.e., top T-cell clones) persisted over 20years, and some of them expanded and exerted a dominating influence on clonality of peripheral T-cell populations. It is thus possible that persistence or expansion of top T-cell clones is a driver of T-cell immunity aging, and therefore represents a potential interventional target.

A Bayesian Semiparametric Model for Radiation Dose-Response Estimation

In evaluating the risk of exposure to health hazards, characterizing the dose-response relationship and estimating acceptable exposure levels are the primary goals. In analyses of health risks associated with exposure to ionizing radiation, while there is a clear agreement that moderate to high radiation doses cause harmful effects in humans, little has been known about the possible biological effects at low doses, for example, below 0.1 Gy, which is the dose range relevant to most radiation exposures of concern today. A conventional approach to radiation dose-response estimation based on simple parametric forms, such as the linear nonthreshold model, can be misleading in evaluating the risk and, in particular, its uncertainty at low doses. As an alternative approach, we consider a Bayesian semiparametric model that has a connected piece-wise-linear dose-response function with prior distributions having an autoregressive structure among the random slope coefficients defined over closely spaced dose categories. With a simulation study and application to analysis of cancer incidence data among Japanese atomic bomb survivors, we show that this approach can produce smooth and flexible dose-response estimation while reasonably handling the risk uncertainty at low doses and elsewhere. With relatively few assumptions and modeling options to be made by the analyst, the method can be particularly useful in assessing risks associated with low-dose radiation exposures.

Circulating Hematopoietic Stem and Progenitor Cells in Aging Atomic Bomb Survivors

It is not yet known whether hematopoietic stem and progenitor cells (HSPCs) are compromised in the aging population of atomic bomb (A-bomb) survivors after their exposure nearly 70 years ago. To address this, we evaluated age- and radiation-related changes in different subtypes of circulating HSPCs among the CD34-positive/lineage marker-negative (CD34(+)Lin(-)) cell population in 231 Hiroshima A-bomb survivors. We enumerated functional HSPC subtypes, including: cobblestone area-forming cells; long-term culture-initiating cells; erythroid burst-forming units; granulocyte and macrophage colony-forming units; and T-cell and natural killer cell progenitors using cell culture. We obtained the count of each HSPC subtype per unit volume of blood and the proportion of each HSPC subtype in CD34(+)Lin(-) cells to represent the lineage commitment trend. Multivariate analyses, using sex, age and radiation dose as variables, showed significantly decreased counts with age in the total CD34(+)Lin(-) cell population and all HSPC subtypes. As for the proportion, only T-cell progenitors decreased significantly with age, suggesting that the commitment to the T-cell lineage in HSPCs continuously declines with age throughout the lifetime. However, neither the CD34(+)Lin(-) cell population, nor HSPC subtypes showed significant radiation-induced dose-dependent changes in counts or proportions. Moreover, the correlations of the proportions among HSPC subtypes in the survivors properly revealed the hierarchy of lineage commitments. Taken together, our findings suggest that many years after exposure to radiation and with advancing age, the number and function of HSPCs in living survivors as a whole may have recovered to normal levels.

Long-term effects of the rain exposure shortly after the atomic bombings in Hiroshima and Nagasaki

The "black rain" that fell after the atomic bombings of Hiroshima and Nagasaki has been generally believed to contain radioactive materials. During 1949-1961 the Atomic Bomb Casualty Commission conducted surveys that included a query about exposure to the rain that fell a short time after the bombings. This article presents the first report of those data in relation to possible adverse health outcomes. This study looked at Life Span Study subjects who were in either city at the time of bombing and had an estimated direct radiation dose from the bombs (n = 86,609). The mortality data from 1950-2005 and cancer incidence data from 1958-2005 were used. Excess relative risks (ERRs) of subjects who were exposed to rain compared to those who reported no rain exposure were calculated using a Poisson regression model. In Hiroshima 11,661 subjects (20%) reported that they were exposed to rain, while in Nagasaki only 733 subjects (2.6%) reported rain exposure. To avoid outcome dependent biases (i.e., recall of exposure after a health outcome has already occurred), the primary analyses were based on events that occurred during 1962-2005. No significant risks due to rain exposure were observed for death due to all causes, all solid cancer or leukemia in Hiroshima. In Nagasaki there was no significantly elevated rain exposure-associated risks for 1962-2005, however, for 1950-2005 there was a weak association for all-cause mortality (ERR = 0.08; 95% confidence interval 0.00006, 0.17; P = 0.05). For incidence of solid cancer and leukemia, no significantly elevated rain exposure risks were observed in either city. These results failed to show deleterious health effects from rain exposure. While these data represent the most extensive set of systematically collected data on rain exposure of the atomic bomb survivors, they are limited by substantial uncertainties regarding exposures and missing individual data, so cautious interpretation is advised.

Handling incomplete smoking history data in survival analysis

While data are unavoidably missing or incomplete in most observational studies, consequences of mishandling such incompleteness in analysis are often overlooked. When time-varying information is collected irregularly and infrequently over a long period, even precisely obtained data may implicitly involve substantial incompleteness. Motivated by an analysis to quantitatively evaluate the effects of smoking and radiation on lung cancer risks among Japanese atomic-bomb survivors, we provide a unique application of multiple imputation to incompletely observed smoking histories under the assumption of missing at random. Predicting missing values for the age of smoking initiation and, given initiation, smoking intensity and cessation age, analyses can be based on complete, though partially imputed, smoking histories. A simulation study shows that multiple imputation appropriately conditioned on the outcome and other relevant variables can produce consistent estimates when data are missing at random. Our approach is particularly appealing in large cohort studies where a considerable amount of time-varying information is incomplete under a mechanism depending in a complex manner on other variables. In application to the motivating example, this approach is expected to reduce estimation bias that might be unavoidable in naive analyses, while keeping efficiency by retaining known information.

Is the association between smoking and the retinal venular diameter reversible following smoking cessation?

PURPOSE

Wider retinal venular caliber is shown to be associated with an increased risk of stroke, and smoking is associated with a wider retinal venular caliber. However, the impact of smoking cessation on the retinal vessels has not been previously reported. We examined this issue in an adult cohort of atomic bomb survivors.

METHODS

In the Adult Health Study of Japanese atomic bomb survivors, 1664 subjects had retinal photographs taken from 2006 to 2008. The central retinal artery and vein equivalents (CRAE and CRVE) were calculated using a semiautomated software program. Multiple surveys have assessed the effects of smoking since 1963. The associations between smoking, the time since cessation, and the retinal vessel caliber were determined using linear mixed effects models.

RESULTS

The CRVE was associated with an increased number of cigarettes smoked per day among women after adjusting for potential confounding factors (age, sex, blood pressure, hypertensive medications, white blood cell count, diabetes, body mass index, lipids, and radiation dose). Females who smoked 10 cigarettes per day had a 6.9-μm wider mean CRVE (P = 0.001) than nonsmokers. Females who had stopped smoking for 10 or more years had a mean CRVE similar to those who had never smoked (191.8 vs. 194.4 μm; P = 0.23). These associations were not observed in males or for CRAE.

CONCLUSIONS

Wider retinal venular caliber is associated with smoking in Japanese females; however, this association becomes nonsignificant after 10 or more years of smoking cessation, suggesting that the impact of smoking on retinal venular dilation is reversible following long-term smoking cessation.

Myositis in primary Sjögren's syndrome: clinical and pathological report

Abstract To clarify the clinical features of myositis complicated with primary Sjögren's syndrome (SS), we studied 89 patients with Sjögren's syndrome (one male and 88 females; mean age 56.0 ± 15.31 years). Myositis was diagnosed from clinical findings, muscle enzymes, electromyographic findings, and muscle biopsy findings. Myositis was diagnosed in 5 of 89 SS patients (5.6%). One patient developed myositis 7 months after the onset of SS. The other four patients were diagnosed with myositis and SS simultaneously. Muscular weakness was mild and slowly progressive over 4-14 months (mean 8.4 months). All patients were able to walk without any assistance at the start of prednisolone therapy. Muscular enzymes were slightly elevated (from 1.5- to 12-fold). All patients tested negative for anti-Jo1 antibody and tested positive for antinuclear antibody. Anti-Ro(SSA) antibody was positive in 4/5 (90%); anti-La(SSB) was positive in 2/5 (40%). Although the clinical features of all patients met the criteria for polymyositis of Bohan, they responded well to small or moderate doses of prednisolone, which could be decreased without a recurrence of muscular weakness in all patients. Myositis with Sjögren's syndrome showed relatively moderate symptoms and responded well to prednisolone. A prospective follow-up of patients may provide further information.

Evaluation of systemic markers of inflammation in atomic-bomb survivors with special reference to radiation and age effects

Past exposure to atomic bomb (A-bomb) radiation has exerted various long-lasting deleterious effects on the health of survivors. Some of these effects are seen even after >60 yr. In this study, we evaluated the subclinical inflammatory status of 442 A-bomb survivors, in terms of 8 inflammation-related cytokines or markers, comprised of plasma levels of reactive oxygen species (ROS), interleukin (IL)-6, tumor necrosis factor α (TNF-α), C-reactive protein (CRP), IL-4, IL-10, and immunoglobulins, and erythrocyte sedimentation rate (ESR). The effects of past radiation exposure and natural aging on these markers were individually assessed and compared. Next, to assess the biologically significant relationship between inflammation and radiation exposure or aging, which was masked by the interrelationship of those cytokines/markers, we used multivariate statistical analyses and evaluated the systemic markers of inflammation as scores being calculated by linear combinations of selected cytokines and markers. Our results indicate that a linear combination of ROS, IL-6, CRP, and ESR generated a score that was the most indicative of inflammation and revealed clear dependences on radiation dose and aging that were found to be statistically significant. The results suggest that collectively, radiation exposure, in conjunction with natural aging, may enhance the persistent inflammatory status of A-bomb survivors.

Conventional case-cohort design and analysis for studies of interaction

BACKGROUND

The case-cohort study design has received significant methodological attention in the statistical and epidemiological literature but has not been used as widely as other cohort-based sampling designs, such as the nested case-control design. Despite its efficiency and practicality for a wide range of epidemiological study purposes, researchers may not yet be aware of the fact that the design can be analysed using standard software with only minor adjustments. Furthermore, although the large number of options for design and analysis of case-cohort studies may be daunting, they can be reduced to a few simple recommendations.

METHODS

We review conventional methods for the design and analysis of case-cohort studies and describe empirical comparisons based on a study of radiation, gene polymorphisms and cancer in the Japanese atomic bomb survivor cohort.

RESULTS

Stratified, as opposed to simple, random subcohort selection is recommended, especially for studies of gene-environment interaction, which are notorious for lacking statistical power. Methods based on the score-unbiased exact pseudo-likelihood (or its analogue with stratified case-cohort data) are recommended for use in conjunction with the asymptotic variance estimator.

CONCLUSIONS

We present an example of how to implement case-cohort analysis methods using SPSS, a popular statistical package that lacks some of the features necessary to directly adapt and implement published methods based on other software platforms. We also illustrate case-control analysis using Epicure, which provides greater risk-modelling flexibility than other software. Our conclusions and recommendations should help investigators to better understand and apply the case-cohort design in epidemiological research.

Improvement of criteria for refractory cytopenia with multilineage dysplasia according to the WHO classification based on prognostic significance of morphological features in patients with refractory anemia according to the FAB classification

In the criteria of refractory cytopenia with multilineage dysplasia (RCMD) according to the WHO (World Health Organization) classification, the frequency threshold concerning dysplasia of each lineage was defined as 10%. To predict overall survival (OS) and leukemia-free survival (LFS) for patients with refractory anemia (RA) according to the French-American-British (FAB) classification, we investigated prognostic factors based on the morphological features of 100 Japanese and 87 German FAB-RA patients, excluding 5q-syndrome. In the univariate analysis of all patients, pseudo-Pelger-Huet anomalies >or=10% (Pelger+), micromegakaryocytes >or=10% (mMgk+), dysgranulopoiesis (dys G) >or=10% and dysmegakaryopoiesis (dys Mgk) >or=40% were unfavorable prognostic factors for OS and LFS (OS; P<0.001, LFS; P<0.001). The prognostic effects of the morphological features were similar in both Japanese and German patients. However, dys Mgk >or=10% was not correlated with OS and LFS. In the multivariate analysis, mMgk+ and dys Mgk>or=40% were adverse prognostic factors for OS for all patients, and dys G >or=10% and dys Mgk>or=40% were adverse prognostic factors for LFS for all patients. On the basis of the present analysis, we propose the following modified morphological criteria for RCMD. Modified RCMD should be defined as FAB-RA, excluding 5q-syndrome with dys G >or=10%, dys Mgk>or=40% or mMgk+.

[Clinical significance of WHO classification and MDS 2000 classification in myelodysplastic syndromes]

Excluding chronic myelomonocytic leukemia, a total of 92 consecutive patients with myelodysplastic syndrome showing less than 20% blasts in the bone marrow were analyzed. We evaluated the clinical significance of the WHO and MDS 2000 classifications by reviewing each MDS patient according to the classification. The WHO criteria classified the MDS patients into 36 with RA, 22 with RCMD and 33 with RAEB, whereas according to the MDS 2000 criteria there were 19 RAEB-I patients and 15 RAEB-II patients. Based on the WHO classification, the RCMD patients had higher platelet counts and percentages of blasts among BM cells than the RA patients (P = 0.0018, P = 0.0001). Twenty percent of the RA patients, 44.8% of the RCMD patients, and 70.8% of the RAEB patients had cytogenetic abnormalities. Among them, the poor karyotype was present in 6.7% of the RA patients, 21.0% of the RCMD patients and 41.6% of the RAEB patients. The rate of acute leukemia death was 14.3% in the RA patients, 67.7% in the RAEB patients and 50.0% in the RCMD patients. Analysis of survival times revealed significant differences between RA and RCMD patients (P = 0.0482). The clinical features of RCMD patients were intermediate between those of RAEB and RA patients. There was no difference between the clinical features of the RAEB-I and RAEB-II patients in the MDS 2000 classification.