Association between Sperm Mitochondrial DNA Copy Number and Concentrations of Urinary Cadmium and Selenium.

Elevated sperm mitochondrial DNA copy number (mtDNAcn) is associated with damage to sperm and poorer measures of semen quality. Exposure to cadmium (Cd) can increase oxidative stress and damage sperm mitochondria. The adverse effects of Cd can potentially be reduced by sufficient selenium (Se). The objective of this study was to examine the associations between sperm mtDNAcn and urinary concentrations of Cd and Se, as well as the Cd/Se molar ratio. Participants were recruited from patients who sought infertility treatment at two hospitals in Japan. Urine and semen specimens and self-administered questionnaires were collected on the day of recruitment. Sperm mtDNAcn was measured in extracted sperm DNA by multiplex real-time qPCR. Urinary Cd and Se concentrations were measured using inductively coupled plasma mass spectrometry, and their molar weights were calculated to obtain the Cd/Se molar ratio. Linear regression was used to estimate associations after adjusting for age, body mass index, smoking, drinking, exercise, varicocele, and hospital of recruitment. Sperm mtDNAcn showed statistically insignificant associations with creatinine-adjusted concentrations of urinary Cd (ß = 0.13, 95% CI -0.18, 0.44) and Se (ß = -0.09, 95% CI -0.54, 0.35), and Cd/Se molar ratio (ß = 0.12, 95% CI -0.13, 0.37). The current study found no evidence of an association between mtDNAcn and urinary concentrations of Cd or Se, or the Cd/Se molar ratio.

[New Methods of Evaluating Health Effects of Combined Exposures to Chemicals and Their Problems to Be Solved].

There are several basic prerequisites for the risk assessment of combined exposures to pesticides and dioxins using human health effects as the endpoint. First, all the target chemical substances exert the same toxicity to humans through the same mechanisms. Second, there is a linear dose-response relationship between the toxicity and effects of individual chemicals. With these two prerequisites, the effects of combined exposures are estimated as the sum of the toxicities of individual chemicals. For example, the toxicities of dioxins are calculated using their toxic equivalent quantities (TEQ) by considering the assigned toxic equivalent factor (TEF) of 2,3,7,8-tetrachlorodibenzo-p-dioxin (2,3,7,8-TCDD) set individually from their isomers and homologs. In conventional epidemiological studies, when the impact of each of multiple chemical substances is examined, methods such as multiple regression analysis or using a generalized linear model (GLM) have been used on the basis of the same prerequisites. However, in practice, some of the chemicals exhibit collinearity in their effects or do not show a linear dose-response relationship. In recent years, there have been several methods developed in the field of machine learning being applied to epidemiological research. Typical examples were methods using Bayesian kernel machine regression (BKMR) and weighted quantile sum (WQS), and the shrinkage method, i.e., using the least absolute shrinkage and selection operator (Lasso) and elastic network model (ENM). In the future, while taking into account the findings of experimental studies in biology, epidemiology, and other fields, it is expected that various methods will be applied and selected.

The ratio of 2nd to 4th digit length and reproductive function of infertile male patients.

Purpose: To investigate the relationship between the ratio of index to ring finger lengths (2D:4D ratio), reflecting androgen exposure in utero, and reproductive function among men. Methods: Male patients (N = 180) who consulted for fertility issues participated in the study. The palms of both hands were scanned, and the 2D:4D ratio was calculated. Data on semen volume, sperm concentration and total motility, total and motile sperm counts, and serum hormone concentrations were obtained. Spearman correlation coefficients between the 2D:4D ratio and hormone and semen quality parameters were calculated. Results: The total sperm count was significantly negatively correlated with the 2D:4D ratio of the left hand (r = -0.154, p  = 0.039) but not with that of the right hand (r = -0.045, p  = 0.548). Testosterone showed weak negative correlations with the 2D:4D ratio in the left (r = -0.142, p  = 0.058) and right (r = - 0.149, p  = 0.046) hands. Follicle-stimulating hormone levels were negatively correlated with the 2D:4D ratios of the left (r = -0.173, p  = 0.020) and right (r = -0.164, p  = 0.027) hands. Other semen quality parameters or luteinizing hormone levels showed no significant correlation with the 2D:4D ratios. Conclusions: No clear associations were observed between the 2D:4D ratios and reproductive function.

Pre-Conceptional Anti-Thyroid Antibodies and Thyroid Function in Association with Natural Conception Rates.

Thyroid functioning is an integral part of the endocrine system that supports conception and pregnancy. Frequent consumption of seafood and iodine by Japanese people may adversely affect their thyroid function. Thus, in this study, we aimed to analyze the associations between iodine intake, thyroid hormones, autoimmunity, and natural conception rates in Japanese women trying to conceive their first child. A prospective study of 24 weeks targeted 80 women with no history of infertility, who did not plan to undergo fertility treatment. Concentrations of urinary iodine concentration and thyroid biomarkers in the serum at enrollment were measured. Thirty-five women naturally conceived during the follow-up. The median (inter-quartile range) urinary concentration of iodine was 297 (165, 500) µg/L. Free triiodothyronine (T3) and free thyroxin (T4) negatively correlated with urinary iodine concentrations. Women with anti-thyroid peroxidase (anti-TPO) ≥ 16 IU/mL had lower conception rates (hazard ratio: 0.28, 95% confidence interval, 0.08-0.92) compared with those with anti-TPO < 16 IU/mL, after adjusting for age and coital frequency. None of anti-thyroglobulin antibody, free T3, free T4, or thyroid-stimulating hormone showed significant associations with conception rate after adjusting for age and coital frequency. The negative association between thyroid autoimmunity and natural conception rates warrants further investigation.

The search for aliens within us: a review of evidence and theory regarding the foetal microbiome.

The microbiome is believed to be established during the birthing process through exposure to the maternal microbiome and immediate external environment. The absence of a microbiome prior to birth is based on the sterile womb hypothesis, which was formulated at the beginning of the 20th century and is supported primarily by the culture-based approach in microbiological studies.Findings of bacterial presence in products of fertilization such as the placenta, amniotic fluid, foetal membranes, and umbilical cord blood in studies using next-generation DNA sequencing technologies began to challenge the sterile nature of the intrauterine environment during gestation. These studies have been mainly criticized by their approach to contamination and inconclusive evidence of viability. The implications of bacterial presence in utero are far reaching in medicine and basic sciences. If commensal bacteria exist in the foetus, antibiotic therapies in pregnancy particularly for asymptomatic cases will need to be re-evaluated. Experimental studies utilizing gnotobiology may also be impacted by a realignment of theory.This review of existing literature aims to provide insight into the existence of bacteria in utero, specifically the foetal microbiome through analysis of experimental evidence and theoretical concepts, and to suggest approaches that may further provide clarity into this inquiry.

Associations between urinary heavy metal concentrations and blood pressure in residents of Asian countries.

BACKGROUND: Previous studies have suggested that exposures to heavy metals (arsenic, cadmium, lead, and selenium) may be associated with differences in blood pressure. However, the findings of these studies have been inconsistent. This study was performed to examine the associations between urinary heavy metal concentrations and blood pressure among residents of four Asian countries (Bangladesh, Indonesia, Nepal, and Vietnam). METHODS: This cross-sectional study examined 1899 adults in four Asian countries. Urinary concentrations of heavy metals were measured by inductively coupled plasma mass spectrometry. A questionnaire survey was administered regarding individual characteristics. Anthropometric measurements (height and weight) were performed. Systolic and diastolic blood pressures were measured after a short rest. Multiple linear regression models were applied to investigate associations between urinary heavy metal concentrations and blood pressure after adjustments for age, sex, and body mass index. RESULTS: The geometric means of the urinary concentrations of arsenic, cadmium, lead, and selenium were 84.6, 0.885, 2.09, and 16.5 µg/g creatinine, respectively. The urinary arsenic concentrations were slightly higher than those typically reported in non-polluted populations, while urinary cadmium, lead, and selenium concentrations were equivalent or slightly lower. The urinary lead concentrations were positively associated with both systolic and diastolic blood pressure, but urinary selenium concentrations were negatively associated with them. CONCLUSIONS: Variations in the urinary concentrations of lead and selenium were associated with blood pressure at low levels of exposure/intake.

Telomere length and urinary 8-hydroxy-2'-deoxyguanosine and essential trace element concentrations in female Japanese university students.

Telomere length is thought to be a biomarker of biological aging. This study examined whether telomere length was associated with urinary concentrations of 8-hydroxy-2'-deoxyguanosine (8-OHdG), a biomarker of oxidative stress, and antioxidative trace elements in 73 female Japanese university students (age: 19.2 ± 0.7 years). We quantified 8-OHdG and selenium in urine by liquid chromatography-mass spectrometry and inductively coupled plasma-mass spectrometry, respectively. Telomere length and urinary concentrations of other essential trace elements (molybdenum, cobalt, and chromium) that were previously measured in the same study participants, were used in this study. We used multiple linear regression analysis to examine the associations of telomere length with urinary 8-OHdG and essential trace element concentrations (covariates: urinary cotinine concentration, age, BMI, and drinking status). The geometric means (geometric standard deviation) of 8-OHdG and selenium were 3.4 (1.5) and 31 (1.3) µg/g creatinine, respectively. Telomere length was not associated with urinary 8-OHdG concentration, but was negatively associated with urinary selenium concentration. In conclusion, telomere length was not associated with urinary 8-OHdG concentration in the young women in this study. Longitudinal studies should be conducted to clarify the association between telomere shortening rate and oxidative stress level.

Fecundability and Sterility by Age: Estimates Using Time to Pregnancy Data of Japanese Couples Trying to Conceive Their First Child with and without Fertility Treatment.

Fecundability, the probability of conception in a month or in a menstrual cycle, varies across and within age groups for both women and men. Fertility treatment has become common in a number of countries including Japan, but its impact on the age pattern of fecundability is unknown. By utilizing the previously collected data on time to pregnancy (TTP) of Japanese couples trying to conceive their first child, the present study aimed to estimate fecundability and sterility by women's age and to assess how the estimates may differ by including or excluding assisted conceptions. Duration between discontinuing contraception and conception (including both natural and assisted) resulted in a live birth was called TTP-all, and the duration ending with natural conception was called TTP-natural. TTP-natural was censored when a participant received fertility consultation or treatment. A zero-inflated beta distribution model was used to estimate a proportion of sterile (zero probability of conception) and a distribution of fecundability for each age group. Parameters of the distribution were estimated using the maximum likelihood method. When TTP-all and TTP-natural were used, the sterile proportion of the whole sample was, respectively, 2% and 14%, and the median (interquartile range) of fecundability was, respectively, 0.10 (0.04, 0.19) and 0.11 (0.05, 0.19). The median (interquartile range) of fecundability was 0.18 (0.10, 0.29) for women aged 24 years or younger and 0.05 (0.02, 0.13) for 35-39 years old when TTP-all was used, and the estimates were quite similar with those based on TTP-natural: it was 0.18 (0.10, 0.29) for women aged 24 years or younger and 0.06 (0.00, 0.15) for 35-39 years old. Exclusion of assisted conceptions resulted in larger proportions of sterility, but it had little impact on median or interquartile ranges of fecundability estimates. Fecundability is overall lower at higher ages, while interquartile ranges are overlapping, suggesting that inter-individual variability of fecundability within an age group is as large as the variability across age groups.

Association between nutrient intake and telomere length in Japanese female university students.

OBJECTIVE: Telomere length can be a biomarker of cumulative oxidative stress and inflammation indicating biological aging. Previous studies examined association of nutrient intake with telomere length targeting middle-aged and elderly individuals. This study examined whether dietary macro- and micronutrient intake was associated with telomere length in young females. METHODS: Seventy-four Japanese young females (median (interquartile range) age was 19 (19 - 20) years) participated. We estimated their intake of nutrients (energy, protein, fat, carbohydrate, essential elements, vitamins, fatty acids, and dietary fibre) using a semi-quantitative food frequency questionnaire and measured telomere length (T/S ratio, the ratio of telomere repeat copy number (T) to single-copy gene number (S)) of DNA extracted from blood by qPCR. The association between telomere length and tertiles of nutrient intake were analysed. RESULTS: The median (interquartile range) of telomere length was 0.70 (0.52 - 0.98). Vitamin A intake was positively associated with telomere length (tertile 1 vs. 2, coefficient [95% confidence interval] = 0.42 [0.12, 0.71]; tertile 1 vs. 3, coefficient [95% confidence interval] = 0.33 [0.04, 0.62]) after adjusting for covariates (age, BMI, passive smoking, and drinking). CONCLUSIONS: Our findings suggest that variation in vitamin A intake might influence telomere attrition in healthy individuals.

Coital Frequency and the Probability of Pregnancy in Couples Trying to Conceive Their First Child: A Prospective Cohort Study in Japan.

Background: Low fertility persists but remains unexplained in Japan. We examined whether the probability of pregnancy was influenced by coital frequency, age, reproductive age (assessed by antimüllerian hormone, AMH), and BMI. Methods: We established a two-year prospective study with a sample of hormonally monitored Japanese women aged 23-34 years wanting to conceive their first child. For a maximum of 24 weeks participants recorded menstrual bleeding, sexual intercourse, ovulation, and pregnancy. Additional information on pregnancy and infertility treatment was collected one and two years after intake. Results: The natural conception rate and coital frequency were both low in this sample. Among 80 participants, 44% (35) naturally conceived in 24 weeks. After two years, 74% (59) of women had delivered or were currently pregnant, 50% (40) due to natural and 24% (19) due to assisted conception, and 5% (4) were lost to follow-up. By two years, 56% (45) of women had sought fertility treatment. In 18% (58/319) of the observed ovarian cycles across 24 weeks there was no intercourse in a fertile period. Higher coital frequency at intake was associated with increased probability of conception by 24 weeks of follow-up (OR 1.23, 95%CI 1.02, 1.47). Chronological age, reproductive age, and BMI were not associated with the probability of pregnancy at 24 weeks. Conclusions: Our results suggest that first, natural conception rates could potentially increase with more frequent and well timed intercourse, and second that further work is needed to understand why even in a motivated sample of women monitoring their fertile periods, both the conception and coitus rates were low.

In-utero arsenic exposure and growth of infants from birth to 6 months of age: a prospective cohort study in rural Bangladesh.

Arsenic exposure in postnatal life impacts the growth of children, but little is known about the effect of in-utero arsenic exposure on growth very early in childhood. The aim of this study was to examine the associations between in-utero arsenic exposure and the growth of infants from birth to 6 months of age using monthly follow-up data. A prospective cohort study was conducted in rural areas of Bangladesh with 108 mother-infant pairs. This study identified a negative association between in-utero arsenic exposure and head circumference of infants 1-6 months of age (coefficient = -1.20, 95% confidence interval [CI]: -1.97, -0.42), and the effect was more pronounced in the earlier ages of 1-3 months (coefficient = -0.88, 95% CI: -1.70, -0.05). Because head circumference is considered as a surrogate of brain size, our findings suggest that in-utero arsenic exposure influences brain growth during an important developmental period.

Cadmium Exposure and Blood Telomere Length in Female University Students in Japan.

Cadmium is a toxic metal found ubiquitously throughout the world. Our study evaluated whether cadmium exposure was associated with telomere length in 73 female university students. Determination of telomere length was performed by quantitative polymerase chain reaction using DNA in blood. Urinary cadmium concentration was measured by inductively coupled plasma mass spectrometry. The students' physiological attributes and lifestyle were surveyed by means of a self-administered questionnaire. The geometric mean of urinary cadmium concentration was 0.312 µg/g creatinine, which was lower than the levels previously reported for Japan. Urinary cadmium concentration was not significantly associated with telomere length, though the exposure level of the present subjects was similar to that of previous study subjects which found significantly negative associations. It is possible that other factors affected telomere length in this study population.

Association between short-term exposure to fine particulate matter and daily emergency room visits at a cardiovascular hospital in Dhaka, Bangladesh.

BACKGROUND: It has been suggested that exposure to fine particulate matter (PM2.5) adversely affects cardiovascular health. However, the effect modifications by individual characteristics and season have been less studied in developing countries where PM2.5 levels are high. OBJECTIVES: To estimate the risks of cardiovascular emergency room visits in relation to daily concentrations of PM2.5 and to assess how these associations can be modified by age, sex, and nutritional status of patients and by season. METHODS: The analytic sample was 6774 adults who visited the emergency room at a cardiovascular disease (CVD) hospital in Dhaka throughout one year (n = 364 days). A time-stratified case-crossover design with conditional Poisson regression analysis was used to estimate the relative risks (RRs) and 95% confidence intervals (CIs) of visits while adjusting for temperature. Stratification was performed by gender, age (<65 and ≥65 years), BMI (underweight, normal weight, overweight), and season (dry summer: February to April; wet summer: May to October; dry winter: November to January). RESULTS: The mean concentration of PM2.5 was 86.1 µg/m3. An IQR increase (103 µg/m3) in PM2.5 at lag 3 was significantly associated with a 12% (RR: 1.12; 95% CI: 1.01-1.23) increase in CVD emergency room visits. No evidence of association was found for the other lags. Underweight and overweight patients showed evidence of increased risk at lag 2 (RR: 1.31; 95% CI: 1.02-1.67) and lag 4 (RR: 1.20; 95% CI: 1.04-1.39), respectively. CONCLUSION: Increases in the daily concentrations of PM2.5 may lead to more cardiovascular emergency room visits in Dhaka, Bangladesh. Response times from ambient exposure to CVD emergency visits may differ by season and the nutritional status of susceptible individuals, necessitating further research.

Urinary 8-Hydroxy-2'-deoxyguanosine (8-OHdG) Concentrations and Menstrual Cycle Characteristics in Female University Students.

Higher concentrations of oxidative stress biomarkers are found in women with polycystic ovary syndrome (PCOS) and endometriosis, conditions linked to irregular menstrual cycles and menstrual pain. The aim of the present study was to test whether women with higher oxidative stress are more likely to show irregular menstrual cycles and severe menstrual pain compared with women with lower oxidative stress. A cross-sectional study was conducted targeting female university students with a mean (SD) age of 20.5 (1.8) years (n = 188). Participants completed a questionnaire on reproductive characteristics and anthropometry and kept a menstrual cycle diary for 5 consecutive months. Urinary 8-hydroxy-2'-deoxyguanosine (8-OHdG), cotinine, and creatinine concentrations were measured once during the study period. The mean (SD) value of the urinary 8-OHdG concentration was 4.7 (2.0) µg/g of creatinine. A total of 1021 menstrual cycles were recorded. The participants were categorized as either having regular (68%) or irregular (18%) cycles or oligomenorrhea (13%) or polymenorrhea (1%). The urinary 8-OHdG concentration did not significantly differ across menstrual cycle regularity or pain categories. Even after adjusting for age, body mass index (BMI), and urinary cotinine concentrations, having irregular cycles or more severe menstrual pain was not associated with urinary 8-OHdG concentration.

U-shaped association between fertility and mortality in a community-based sample of Japanese women.

BACKGROUND: Prospective cohort studies of contemporary populations in both Western and Asian settings have reported a U-shaped association between fertility and mortality. We examined whether an association exists between fertility and all-cause and cause-specific mortality in a sample of Japanese women. METHODS: A prospective cohort study was conducted in one rural and one urban community in Gunma Prefecture, Japan, in 1993. A follow-up survey was conducted in the year 2000 in 4858 women aged 47-77 years, and information on demographic and lifestyle characteristics was collected. Mortality and migration data through December 2008 were obtained. A Cox proportional hazard model was used to examine the relationship between parity and mortality. RESULTS: Compared with women with 2-4 children (reference group), higher total mortality was observed among women with 0-1 or 5+ children. Low (HR 1.7, 95% CI 1.2 to 2.3) and high (HR 2.1, 95% CI 1.0 to 4.7) parities were both associated with higher all-cause mortality even after adjusting for potential confounders. Mortality due to ischaemic heart disease exhibited a significant association with parity; the HRs were 3.2 (95% CI 1.1 to 9.2) for women with 0-1 child and 8.7 (95% CI 1.7 to 45.5) for women with 5 or more children. No significant association was observed for mortality from malignancies, cancer of the digestive system, cardiovascular disease or cerebrovascular disease. CONCLUSIONS: There exists a U-shaped association between parity and all-cause mortality and cause-specific mortality due to ischaemic heart disease among Japanese women.

Inter- and intra-individual variation in urinary concentrations of parabens in male and female Japanese subjects.

We evaluated the representativeness of concentrations of parabens in a spot urine sample for the assessment of long-term exposure levels. Urine sample was taken monthly from 10 male Japanese subjects (35.9 ± 6.8 years) and 12 female Japanese university students (21.1 ± 0.4 years) for 5 months and measured for methyl (MP), ethyl (EP), propyl (PP) and butyl (BP) parabens by liquid chromatography-tandem mass spectrometry. Median (min-max) specific-gravity-adjusted urinary concentrations of the male group (n = 10) were 39.7 (2.99-268), 1.69 (< 0.045-75.2), 0.569 (< 0.11-123) and 0.0264 (< 0.020-24.4) ng mL-1 for MP, EP, PP and BP, respectively. Those of the female group (n = 12) were 283 (5.49-1687), 9.30 (0.290-487), 22.9 (< 0.11-307) and 3.76 (< 0.020-135) ng mL-1, respectively, which were significantly higher than those of the male group. Intra-class correlation coefficients (ICCs) were calculated for the four parabens to find 0.56, 0.58, 0.39 and 0.28 for MP, EP, PP and BP, respectively, in the male group, and 0.40, 0.43, 0.41 and 0.37 for MP, EP, PP and BP, respectively, in the female group. The results suggested that four paraben concentrations in a spot urine sample moderately reflected long-term paraben exposure of Japanese subjects. Source of exposure to parabens is also discussed.

Preterm birth rates in Japan from 1979 to 2014: Analysis of national vital statistics.

AIM: Secular trends of preterm birth in Japan between 1979 and 2014 were examined to determine whether changes could be explained by a shift in the distribution of maternal age at delivery and parity and/or by changes in age-specific preterm birth rates. METHODS: Live birth data for 1979 to 2014 were obtained from the Japanese Ministry of Health, Labour and Welfare. Analyses were limited to singleton children born in Japan (n = 43 632 786). Preterm birth was defined using two cut-offs at < 37 or < 34 weeks of gestation. Crude and standardized rates of preterm birth were calculated for firstborn and later-born singletons by maternal age at delivery for specific time periods. RESULTS: Throughout the study period, the rates of preterm birth (both at < 37 and < 34 weeks of gestation) were higher among mothers aged 20 and younger, and mid-30s and older, compared to mothers in their 20s or early 30s. The rates of preterm birth at < 37 (but not at < 34) weeks decreased for mothers aged in their late 30s and 40s, and increased for mothers in their 20s and early 30s. Standardized rates of preterm birth showed a secular increase for preterm births at < 37 but not < 34 weeks of gestation. CONCLUSION: The rates of preterm birth among mothers aged in their 20s and early 30s increased between 1979 and 2014, which contributed to the secular increase in rates of preterm birth at < 37 weeks.

Association of Asian Dust with daily medical consultations for pollinosis in Fukuoka City, Japan.

BACKGROUND: The objective is to examine the association between AD and the daily number of medical consultations for pollinosis in Fukuoka City. METHODS: We analyzed 65,488 daily medical consultations for pollinosis from 4 clinics in Fukuoka City from February to April, 1989-2012. Time-series analyses were performed to estimate the clinic-specific relative risk (RR) of clinical pollinosis associated with AD, adjusting for airborne pollen, suspended particulate matter (SPM), meteorological and temporal factors. Delayed effects were considered. The association with SPM was also examined given its relationship with AD. The clinic-specific RRs were combined using meta-analytic technique. RESULTS: AD on the same day (lag 0) and the previous 3 to 5 days (lags 3, 4, and 5) was positively associated with the risk of medical consultations for pollinosis. Clinic visits were 21.5% (95% confidence interval 3.1% - 43.1%) higher when there was an AD event (across lags 0-5). The association with SPM showed comparable lag structure, but with smaller effect estimates. When stratified by the occurrence of AD, the estimated risk increases associated with SPM did not differ between the AD-affected and AD-free days. CONCLUSION: AD is associated with an increased risk of medical consultations for pollinosis in spring. More research is needed to elucidate the roles of air particles with different sizes.

Interactive effects of specific fine particulate matter compositions and airborne pollen on frequency of clinic visits for pollinosis in Fukuoka, Japan.

BACKGROUND: Previous studies have revealed the interactive effects of airborne pollen and particulate matter on the daily consultations for pollinosis, but it is uncertain which compositions are responsible. This study aimed to investigate the interactive effects of specific PM2.5 compositions and airborne pollen on the daily number of clinic visits for pollinosis in Fukuoka. METHODS: We obtained daily data on pollen concentrations, PM2.5 compositions, PM2.5 mass, gaseous pollutants (SO2, NO2, CO, and O3), and weather variables monitored in Fukuoka between February and April, 2002-2012. In total, 73,995 clinic visits for pollinosis were made at 10 clinics in Fukuoka Prefecture during the study period. A time-stratified case-crossover design was applied to examine the interactive effects. The concentrations of PM2.5 and its compositions were stratified into low (<15th percentile), moderate (15th-85th percentile), and high (>85th percentile) levels, and the association between airborne pollen and daily clinic visits for pollinosis was analyzed within each level. RESULTS: We found a significant interaction between specific PM2.5 compositions and airborne pollen. Specifically, the odds ratio of daily clinic visits for pollinosis per interquartile increase in pollen concentration (39.8 grains/cm2) at the average cumulative lag of 0 and 2 days during high levels of non-sea-salt Ca2+ was 1.446 (95% CI: 1.323-1.581), compared to 1.075 (95% CI: 1.067-1.083) when only moderate levels were observed. This result remained significant when other air pollutants were incorporated into the model and was fairly persistent even when different percentile cut-off points were used. A similar interaction was found when we stratified the data according to non-sea-salt SO42- levels. This finding differed from estimates made according to PM2.5 and NO3- levels, which predicted that the effects of pollen were strongest in the lower levels. CONCLUSIONS: Associations between airborne pollen and daily clinic visits for pollinosis could be enhanced by high levels of specific PM2.5 compositions, especially non-sea-salt Ca2+.

Airborne pollen and suicide mortality in Tokyo, 2001-2011.

Prior research has indicated that pollen might be linked to suicide mortality although the few studies that have been undertaken to date have produced conflicting findings and been limited to Western settings. This study examined the association between the level of airborne pollen and suicide mortality in Tokyo, Japan in the period from 2001 to 2011. The daily number of suicide deaths was obtained from the Japanese Ministry of Health, Labour and Welfare, with pollen data being obtained from the Tokyo Metropolitan Institute of Public Health. A time-stratified case-crossover study was performed to examine the association between different levels of pollen concentration and suicide mortality. During the study period there were 5185 male and 2332 female suicides in the pollen season (February to April). For men there was no association between airborne pollen and suicide mortality. For women, compared to when there was no airborne pollen, the same-day (lag 0) pollen level of 30 to <100 grains per cm2 was associated with an approximately 50% increase in the odds for suicide (e.g. 30 to <50 grains per cm2: odds ratio 1.574, 95% confidence interval 1.076-2.303, p=0.020). The estimates remained fairly stable after adjusting for air pollutants and after varying the cut-points that defined the pollen levels. Our results indicate that pollen is associated with female suicide mortality in Tokyo.