Chris Fook Sheng Ng

Characterizing the effect of summer temperature on heatstroke-related emergency ambulance dispatches in the Kanto area of Japan

Despite rising concern on the impact of heat on human health, the risk of high summer temperature on heatstroke-related emergency dispatches is not well understood in Japan. A time-series study was conducted to examine the association between apparent temperature and daily heatstroke-related ambulance dispatches (HSAD) within the Kanto area of Japan. A total of 12,907 HSAD occurring from 2000 to 2009 in five major cities—Saitama, Chiba, Tokyo, Kawasaki, and Yokohama—were analyzed. Generalized additive models and zero-inflated Poisson regressions were used to estimate the effects of daily maximum three-hour apparent temperature (AT) on dispatch frequency from May to September, with adjustment for seasonality, long-term trend, weekends, and public holidays. Linear and non-linear exposure effects were considered. Effects on days when AT first exceeded its summer median were also investigated. City-specific estimates were combined using random effects meta-analyses. Exposure-response relationship was found to be fairly linear. Significant risk increase began from 21xa0°C with a combined relative risk (RR) of 1.22 (95xa0% confidence interval, 1.03–1.44), increasing to 1.49 (1.42–1.57) at peak AT. When linear exposure was assumed, combined RR was 1.43 (1.37–1.50) per degree Celsius increment. Overall association was significant the first few times when median AT was initially exceeded in a particular warm season. More than two-thirds of these initial hot days were in June, implying the harmful effect of initial warming as the season changed. Risk increase that began early at the fairly mild perceived temperature implies the need for early precaution.

Particulate matter modifies the association between airborne pollen and daily medical consultations for pollinosis in Tokyo

Pollen from Japanese cedar (sugi) and cypress (hinoki) trees is responsible for the growing prevalence of allergic rhinitis, especially pollinosis in Japan. Previous studies have suggested that air pollutants enhance the allergic response to pollen in susceptible individuals. We conducted a time-stratified case-crossover study to examine the potential modifying effects of PM2.5 and suspended particulate matter (SPM) on the association between pollen concentration and daily consultations for pollinosis. A total of 11,713 daily pollinosis cases (International Classification of Diseases, ICD-10, J30.1) from January to May, 2001-2011, were obtained from a clinic in Chiyoda, Tokyo. Daily pollen counts and the daily mean values of air pollutants (PM2.5, SPM, SO2, NO2, CO, and O3) were collected from monitoring stations across Tokyo. The effects of pollen were stratified by the level of PM2.5 and SPM to examine the interaction effect of pollen and particulate pollutants. We found a statistically significant interaction between pollen concentration and PM2.5/SPM. On days with a high level of PM2.5 (>95th percentile), an interquartile increase in the mean cumulative pollen count (an average of 28 pollen grains per cm(2) during lag-days 0 to 5) corresponded to a 10.30% (95%CI: 8.48%-12.16%) increase in daily new pollinosis cases, compared to 8.04% (95%CI: 7.28%-8.81%) on days with a moderate level of PM2.5 (5th-95th percentile). This interaction persisted when different percentile cut-offs were used and was robust to the inclusion of other air pollutants. A similar interaction pattern was observed between SPM and pollen when a less extreme cut-off for SPM was used to stratify the effect of pollen. Our study showed the acute effect of pollen was greater when the concentration of air particulate pollutant, specifically PM2.5 and SPM, was higher. These findings are consistent with the notion that particulate air pollution may act as an adjuvant that promotes allergic disease (i.e. pollinosis).

Ambient air pollution and suicide in Tokyo, 2001–2011

BACKGROUNDnSome evidence suggests an association may exist between the level of air pollution and suicide mortality. However, this relation has been little studied to date. The current study examined the association in Tokyo, Japan.nnnMETHODSnSuicide mortality data for Tokyo for the 11-year period 2001-2011 were obtained together with data on four air pollutants: fine particulate matter (PM2.5), suspended particulate matter (SPM), sulphur dioxide (SO2) and nitrogen dioxide (NO2). A time-stratified case-crossover study design was used to examine the daily association between the level of air pollution and suicide mortality.nnnRESULTSnDuring the study period there were 29,939 suicide deaths. In stratified analyses an interquartile range (IQR) increase in the same-day concentration of NO2 was linked to increased suicide mortality among those aged under 30 (percentage change: 6.73%, 95% CI: 0.69-13.12%). An IQR increase in PM2.5 and SO2 was associated with a 10.55% (95% CI: 2.05-19.75%) and 11.47% (95% CI: 3.60-19.93%) increase, respectively, in suicide mortality among widowed individuals for mean exposure on the first four days (average lags 0-3). Positive associations were observed for the air pollutants in the summer although associations were reversed in autumn.nnnLIMITATIONSnWe relied on monitoring data to approximate individual exposure to air pollutants.nnnCONCLUSIONSnHigher levels of air pollution are associated with increased suicide mortality in some population subgroups in Tokyo. Further research is needed to elucidate the mechanisms linking air pollutants and suicide in this setting.

Seasonal variation in the acute effects of ozone on premature mortality among elderly Japanese

We conducted a multicity time-series study using monitoring data to assess seasonal patterns of short-term ozone–mortality association among elderly aged 65xa0years and over in Japan. Daily exposure to ambient ozone was computed using hourly measurements of photochemical oxidants available at multiple monitoring stations in each city. Effects of ozone on daily all-cause non-accidental, cardiovascular, and respiratory mortality were estimated using distributed lag linear models, controlling for confounding by temporal, day of the week, temperature, and flu epidemics. City-level effect estimates were combined using inverse variance meta-analysis. In spring and autumn, a 10-ppbv increase of daily maximum 8-h average ozone concentration in the previous 3xa0days was associated with 0.69xa0% (95xa0% confidence interval (CI): 0.27–1.10), 1.07xa0% (0.34–1.82), and 1.77xa0% (0.78–2.77) increases in daily all-cause, cardiovascular, and respiratory mortality, respectively. Forward displacement of respiratory mortality was large during the cold season despite lower ozone concentration. Results were generally independent of fine particulate matter and nitrogen dioxide. Findings suggest significant mortality effects of short-term ozone exposure among the elderly during the moderate season. Those with underlying respiratory diseases were susceptible, even during winter.

Association of cadmium and arsenic exposure with salivary telomere length in adolescents in Terai, Nepal

BACKGROUNDnCadmium and arsenic are ubiquitous metals commonly found in the environment which can harm human health. A growing body of research shows telomere length as a potential biomarker of future disease risk. Few studies have examined the effects of metals on telomere length and none have focused on adolescents.nnnOBJECTIVESnIn this study, the impact of cadmium and arsenic on salivary telomere length was studied in adolescents in Terai, Nepal.nnnMETHODSnAdolescents aged 12-16 years old (n=351)were recruited where questionnaire interviews and both saliva and urine collection took place. Telomere length was determined by quantitative polymerase chain reaction using DNA extracted from saliva. Urinary cadmium and arsenic concentration were measured by inductively coupled plasma mass spectrometry. Multivariable linear regression was used to examine associations between urinary metals and salivary telomere length.nnnRESULTSnThe geometric means and standard deviations of cadmium and arsenic were 0.33±0.33μg/g creatinine and 196.0±301.1μg/g creatinine, respectively. Urinary cadmium concentration was negatively associated with salivary telomere length after adjustment for confounders (β=-0.24, 95% CI -0.42,-0.07). Arsenic showed positive associations with telomere length but did not reach statistical significance.nnnCONCLUSIONSnThis is the first study to demonstrate that cadmium may shorten adolescent telomeres, even at exposure levels that may be considered low. These results agree with prior experimental and adult epidemiological studies, and also help identify the mechanism of DNA damage by cadmium. This study expanded current evidence on the harmful effects of cadmium exposure on telomere length even to adolescents.

airborne pollen and suicide mortality in Tokyo, 2001–2011

&NA; 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. HighlightsPrior research has indicated that airborne pollen may be associated with suicide.In Tokyo in 2001–2011 the level of airborne pollen was linked to suicide mortality.Only female suicide was associated with the level of airborne pollen.

Seasonality of child and adolescent injury mortality in Japan, 2000-2010

ObjectiveInjury is the leading cause of death among children and adolescents in Japan. Despite this, until now there has been comparatively little research on this phenomenon. The purpose of this study was to examine if there was seasonal variation in child and adolescent injury mortality in Japan in 2000–2010.MethodsVital statistics injury mortality data were obtained from the Ministry of Health, Labour and Welfare of Japan. The seasonality of the major causes of unintentional injury (transport accidents, drowning and suffocation) and intentional injury (suicide and homicide) mortality was examined for children and adolescents aged 0–19. Incidence ratios (IR) with 95xa0% confidence intervals (CI) were calculated to determine the difference between the numbers of observed and expected seasonal deaths.ResultsThe annual average injury mortality rate among children and adolescents was 9.0 per 100,000. Deaths from transport accidents, drowning, suffocation and suicide had a significant seasonality. There was a summer peak for transport accidents (IR 1.15, 95xa0% CI 1.10–1.19) and drowning (IR 2.00, 95xa0% CI 1.88–2.11), a spring peak for suicide (IR 1.09, 95xa0% CI 1.04–1.14), while the incidence of suffocation was higher in winter (IR 1.12, 95xa0% CI 1.03–1.21).ConclusionChild and adolescent injury mortality from transport accidents, drowning, suffocation and suicide has a pronounced seasonality in Japan. More research is now needed to find the circumstances underpinning different forms of injury mortality in different periods of the year so that effective interventions can be designed and implemented to reduce the burden of injury mortality among Japanese children.

Heat-Related Mortality in Japan after the 2011 Fukushima Disaster: An Analysis of Potential Influence of Reduced Electricity Consumption

Background: In March 2011, the Great East Japan Earthquake devastated several power stations and caused severe electricity shortages. This accident was followed by the implementation of policies to reduce summer electricity consumption in the affected areas, for example, by limiting air-conditioning (AC) use. This provided a natural experimental scenario to investigate if these policies were associated with an increase in heat-related mortality. Objectives: We examined whether the reduced electricity consumption in warm season modified heat-related mortality from 2008 to 2012. Methods: We conducted prefecture-specific interrupted time-series (ITS) analyses to compare temperature–mortality associations before and after the earthquake, and used meta-analysis to generate combined effect estimates for the most affected and less affected areas (prefectures with >10% or ≤10% reductions in electricity consumption, respectively). We then examined whether the temperature–mortality association in Tokyo, one of the most affected areas, was modified by the percent reduction in electricity consumption relative to expected consumption for comparable days before the earthquake. Results: Contrary to expectations, we estimated a 5–9% reduction in all-cause heat-related mortality after the earthquake in the 15 prefectures with the greatest reduction in electricity consumption, and little change in the other prefectures. However, the percent reduction in observed vs. expected daily electricity consumption after the earthquake did not significantly modify daily heat-related mortality in Tokyo. Conclusions: In the prefectures with the greatest reductions in electricity consumption, heat-related mortality decreased rather than increased following the Great East Japan Earthquake. Additional research is needed to determine whether this finding holds for other populations and regions, and to clarify its implications for policies to reduce the consequences of climate change on health. https://doi.org/10.1289/EHP493

Birthdays are associated with an increased risk of suicide in Japan : Evidence from 27,007 deaths in Tokyo in 2001-2010

BACKGROUNDnPrevious research has produced conflicting findings concerning whether birthdays are associated with an increased risk of suicide. This study examined the association in Tokyo, Japan.nnnMETHODSnSuicide data (ICD-10 codes X60-X84) for the period 2001-2010 were obtained from the Japanese Ministry of Health, Labour and Welfare. A time-stratified case-crossover design was used with conditional logistic regression analysis being performed to estimate within-subject birthday exposures while controlling for meteorological conditions and public holidays.nnnRESULTSnThere were 27,007 suicides in the study period. For males the 5 days before the birthday and the week after the birthday were associated with significantly higher odds for suicide with the odds ratio being highest on the actual birthday (OR =1.677, 95% CI: 1.294, 2.172). For females, significantly higher odds for completed suicide were observed 7-11 days before the birthday. Stratified analyses showed different at risk time patterns among men from different age groups, and that married men had higher odds for suicide on, and for the 4 days before and in the 2 weeks after their birthday.nnnLIMITATIONSnWe lacked detailed information on suicides which would have enabled a better understanding of the observed associations.nnnCONCLUSIONSnBirthdays are associated with an increased risk for suicide in Tokyo, Japan. Health professionals who work with individuals at risk of suicide should be made aware that birthdays are associated with an elevated suicide risk. This information should also be communicated in wider suicide prevention campaigns.

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

BACKGROUNDnIt 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.nnnOBJECTIVESnTo 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.nnnMETHODSnThe analytic sample was 6774 adults who visited the emergency room at a cardiovascular disease (CVD) hospital in Dhaka throughout one year (nu202f=u202f364u202fdays). 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 ≥65u202fyears), BMI (underweight, normal weight, overweight), and season (dry summer: February to April; wet summer: May to October; dry winter: November to January).nnnRESULTSnThe mean concentration of PM2.5 was 86.1u202fμg/m3. An IQR increase (103u202fμg/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.nnnCONCLUSIONnIncreases 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.