Exploring the comprehensive link between climatic factors and vegetation productivity in China.

Understanding the influence of climatic factors on vegetation dynamics and cumulative effects is critical for global sustainable development. However, the response of vegetation to climate and the underlying mechanisms in different climatic zones remains unclear. In this study, we analyzed the response of vegetation gross primary productivity (GPP) to climatic factors and the cumulative effects across various vegetation types and climatic zones, utilizing data on precipitation (Pr), temperature (Ta), and the standardized precipitation evapotranspiration index (SPEI). The results showed that: (1) GPP showed significant differences among the seven climatic zones, with the highest value observed in zone VII, reaching 1860.07 gC·m- 2, and the lowest in zone I, at 126.03 gC·m- 2. (2) GPP was significantly and positively correlated with temperature in climatic zones I, IV, V, and VI and with precipitation in climatic zones I, II, and IV. Additionally, a significant positive correlated was found between SPEI and GPP in climatic zones I, II, and IV. (3) Drought exerted a cumulative effect on GPP in 45.10% of the regions within China, with an average cumulative duration of 5 months. These effects persisted for 6-8 months in zones I, II, and VII, and for 2-4 months in zones III, IV and VI. Among different vegetation types, forests experienced longest cumulative effect time of 6 months, followed by grasslands (5 months), croplands (4 months), and shrublands (4 months). The cumulative time scale decreased with increasing annual SPEI. The varying responses and accumulation of GPP to drought among different vegetation types in various climatic zones underscore the complexity of vegetation-climate interactions the response and accumulation of GPP to drought.

Dynamics of solar-induced chlorophyll fluorescence (SIF) and its response to meteorological drought in the Yellow River Basin.

Solar-induced chlorophyll fluorescence (SIF) has been used since its discovery to characterize vegetation photosynthesis and is an effective tool for monitoring vegetation dynamics. Its response to meteorological drought enhances our comprehension of the ecological consequences and adaptive mechanisms of plants facing water scarcity, informing more efficient resource management and efforts in mitigating climate change. This study investigates the spatial and temporal patterns of SIF and examines how vegetation SIF in the Yellow River Basin (YRB) responds to meteorological drought. The findings reveal a gradual southeast-to-northwest decline in SIF across the Yellow River Basin, with an overall increase-from 0.1083 W m-2µm-1sr-1 in 2001 to 0.1468 W m-2µm-1sr-1 in 2019. Approximately 96% of the YRB manifests an upward SIF trend, with 75% of these areas reaching statistical significance. The Standardized Precipitation Evapotranspiration Index (SPEI) at a time scale of 4 months (The SPEI-4), based on the Liang-Kleeman information flow method, is identified as the most suitable drought index, adeptly characterizing the causal relationship influencing SIF variations. As drought intensified, the SPEI-4 index markedly deviated from the baseline, resulting in a decrease in SIF values to their lowest value; subsequently, as drought lessened, it gravitated towards the baseline, and SIF values began to gradually increase, eventually recovering to near their annual maximum. The key finding is that the variability of SIF with SPEI is relatively pronounced in the early growing season, with forests demonstrating superior resilience compared to grasslands and croplands. The responsiveness of vegetation SIF to SPEI can facilitate the establishment of effective drought early warning systems and promote the rational planning of water resources, thereby mitigating the impacts of climate change.

Spatial and temporal variations of ecosystem water use efficiency and its response to soil moisture drought in a water-limited watershed of northern China.

Drought synchronously affects the water cycle and interferes with the carbon cycle in terrestrial ecosystems. Ecosystem water use efficiency (WUE), serving as a vital metric for assessing the interplay between water and carbon cycles, has found extensively use in exploring how ecosystems responses to drought. However, the effects of soil moisture drought on WUE are still poorly recognized. Taking Ziya River Basin as an example, the spatial-temporal variations of WUE from 2001 to 2020 were estimated by the Penman-Monteith-Leuning Version 2 (PML-V2) data. Based on the Standardized Soil Moisture Index (SSI) calculated from Soil Moisture of China by in situ data, version 1.0 (SMCI1.0) data, the sensitivity and thresholds of different vegetation WUE to drought magnitudes were investigated, and the influences of both lagged and cumulative effects of drought on WUE were further analyzed. Results showed that the annual mean WUE was 2.160 ± 0.975 g C kg-1 H2O-1 in the Ziya River Basin, with a significant increasing trend of 0.037 g C kg-1 H2O-1 yr-1 (p < 0.05). For all the vegetation types, the WUE reached the maximum value at a certain drought threshold (SSI = -1.5 ± 0.1). The dominant factor controlling WUE sensitivity to drought changed from evapotranspiration (ET) to gross primary production (GPP) when severe drought transformed into extreme drought. Significant lagged and cumulative effects were found in the response of WUE to drought in nearly 58.64 % (72.94 %) of the study area, with an average time scale of 6.65 and 2.11 months (p < 0.05) respectively. Drought resistance in descending order was: forest > shrub > grassland > cropland. Our findings enrich the understanding of the coupled carbon and water cycle processes in terrestrial ecosystems and their response to soil moisture drought in the context of global climate change.

Satellite monitoring reveals short-term cumulative and time-lag effect of drought and heat on autumn photosynthetic phenology in subtropical vegetation.

Comparing with the effect of the average climate change on vegetation phenology, the impacts of extreme climate events remain unclear, especially considering their characteristic cumulative and time-lag effects. Using solar-induced chlorophyll fluorescence (SIF) satellite records, we investigated the cumulative and time-lag effects of drought and heat events on photosynthesis, particularly for the end date of autumn photosynthesis (EOP), in subtropical vegetation in China. Our results showed a negative effect of drought on the delay of EOP, with the cumulative effect on 30.12% (maximum continuous dry days, CDD), 34.82% (dry days, DRD), and 26.14% (dry period, DSDI) of the study area and the general time-lag effect on 50.73% (maximum continuous dry days), 56.61% (dry days), and 47.55% (dry period) of the study area. The cumulative and lagged time were 1-3 months and 2-3 months, respectively. In contrast, the cumulative effect of heat on EOP was observed in 16.27% (warm nights, TN90P), 23.66% (moderate heat days, TX50P), and 19.19% (heavy heat days, TX90P) of the study area, with cumulative time of 1-3 months. The lagged time was 3-4 months, detected in 31.02% (warm nights), 45.86% (moderate heat days), and 36.52% (heavy heat days) of the study area. At the vegetation community level, drought and heat had relatively rapid impacts on EOP in the deciduous broadleaved forest, whereas evergreen forests and bushes responded to heat slowly and took a longer time. Our results revealed that drought and heat have short-term cumulative and time-lag effects on the EOP of subtropical vegetation in China, with varying effects among different vegetation types. These findings provide new insights into the effect of drought and heat on subtropical vegetation and confirm the need to consider these effects in the development of prediction models of autumn phenology for subtropical vegetation.

Combined effects of high sensitivity C-reactive protein and triglyceride-glucose index on risk of cardiovascular disease among middle-aged and older Chinese: Evidence from the China Health and Retirement Longitudinal Study.

BACKGROUND AND AIMS: High sensitivity C-reactive protein (hsCRP) and triglyceride glucose (TyG) index were proved to be independent risk factors of cardiovascular disease (CVD). However, individual hsCRP or TyG index might not provide sufficient predictive value on CVD risk. The current study aimed to evaluate the cumulative effect of hsCRP and TyG index on CVD risk prospectively. METHODS AND RESULTS: A total of 9626 participants were enrolled in the analysis. The TyG index was calculated as ln(triglyceride [mg/dL] × fasting glucose [mg/dL]/2). The primary outcome was new-onset CVD events (cardiac events or stroke), and the secondary outcomes were new-onset cardiac events and stroke, separately. Participants were divided into 4 groups through the median of hsCRP and TyG index. Hazard ratios (HRs) and 95% confidence intervals (CIs) were estimated using multivariable Cox proportion hazard models. From 2013 to 2018, 1730 participants experienced CVD (570 stroke and 1306 cardiac events). Linear associations were found between hsCRP, TyG index, hsCRP/TyG ratio and CVD (all p < 0.05). Compared to participants with low hsCRP/low TyG index, multivariable adjusted HRs (95% CIs) for those with high hsCRP/high TyG index were 1.17 (1.03-1.37) for CVD. No interaction of hsCRP and TyG index was found on CVD (p-interaction ≥0.05). Furthermore, adding hsCRP and TyG index simultaneously to conventional risk model improved risk reclassification for CVD, stroke and cardiac events (all p < 0.05). CONCLUSION: The present study suggested combination of hsCRP and TyG index might better improved the ability for risk stratification of CVD among middle-aged and older Chinese.

Critical window for the association between early electronic screen exposure and hyperactive behaviors in preschool children.

Electronic screens have become an integral part of modern life, accompanied with growing concerns for children's neuropsychological development. This study aimed to evaluate the associations between measures of early life screen exposure and hyperactive behaviors among preschool children. The study also aimed to investigate their cumulative effects and the critical window for these associations. A cross-sectional survey was conducted among 52 625 mother-child dyads at preschools in LongHua District of Shenzhen, China. A self-administered structured questionnaire was used to assess socio-demographic characteristics, duration of children's electronic screen exposure in each of the first 3 years following birth and the presence of current hyperactive behaviors. A series of logistic regression models were used to examine the relationship between previous screen time and current hyperactive behaviors. A crossover analysis was used to explore the critical window for a significant relationship between screen time and hyperactive behaviors. We found that exposure to electronic screens in the first 3 years of life was associated with hyperactive behaviors in preschool children. A cumulative effect was shown in children with an average daily screen time less than 60 min, with adjusted ORs increasing from 1.262 to 1.989 as screen exposure years increased from 1 to 3 years. A critical window was identified in that children in the first 2 years after birth were vulnerable to electronic screen exposure. Exposure to televisions, mobile phones, and computers were all related to elevated risks for hyperactive behaviors. In conclusion, early screen exposure appears to increase the risk for hyperactive behaviors in preschool children with the presence of a cumulative effect, a critical window and different electronic screens having similar effects.

Revisiting the cumulative effects of drought on global gross primary productivity based on new long-term series data (1982-2018).

Drought has broad and deep impacts on vegetation. Studies on the effects of drought on vegetation have been conducted over years. Recently, the cumulative effect of drought is recognized as another key factor affecting plant growth. However, global-scale studies on this phenomenon are still lacking. Thus, based on new satellite based gross primary productivity (GPP) and multi-temporal scale Standardized Precipitation Evapotranspiration Index data sets, we explored the cumulative effect duration (CED) of drought on global vegetation GPP and analyzed its variability across elevations and climatic zones. The main findings were as follows: (1) The cumulative effect of drought on GPP was widespread, with an average CED of 4.89 months. (2) CED of drought on GPP varied among vegetation types. Specifically, grasslands showed the longest duration, with an average value of 5.28 months, followed by shrublands (5.09 months), wetlands (5.03 months), croplands (4.85 months), savannas (4.58 months), and forestlands (4.57 months). (3) CED of drought on GPP changes with climate conditions. It decreased with the decrease of precipitation in the driest month (Pdry ) and mean annual precipitation in tropical and arid climate zones, respectively. In both temperate and cold climate zones, CED of drought on GPP was shorter in areas with dry winter than that in areas with dry summer. It increased with the decrease of mean annual air temperature in tropical climate zones and decreased with the increase of summer temperature in temperate and cold climatic zones. (4) With increasing elevation, CED of drought on GPP showed a pattern of increasing (0-3000 m), then decreasing (3000-5000 m), and increasing again (>5000 m). Our findings highlight the heterogeneity of CED of drought on GPP, owing to differences in vegetation types, long-term hydrothermal conditions, elevation, etc. The results could deepen our understanding of the effects of drought on global vegetation.

Dietary variety relates to gut microbiota diversity and abundance in humans.

PURPOSE: We aim to investigate the relationship between gut microbiota and dietary variety in a Chinese population using Dietary Variety Score (DVS), an index of dietary variety, as little has studied the relationship of dietary variety and gut microbiota in a general population. METHODS: In this cross-sectional study, recruited participants were conducted with face-to-face interview to collect information on 24-h food intake and dietary consumption using a valid food frequency questionnaire. Subjects (n = 128) were divided as high and low DVS groups by the median of DVS after rigorously matching for confounding factors. The gut microbiota was assessed by 16S rRNA sequencing and the correlations between key phylotypes and DVS, Index of Nutritional Quality (INQ) and clinical indices were examined using generalized linear model in negative binomial regression. RESULTS: Higher score of DVS, INQVB6, INQVE and INQZn exhibited higher α-diversity. DVS was correlated with INQ and six genera. Among the DVS-correlated genera, Turicibacter, Alistipes and Barnesiella were positively correlated with INQVE, INQZn and INQCu, individually or in combination, while Cetobacterium was negatively correlated with INQCu, INQZn and INQVE. The abundance of Coprococcus and Barnesiella increased with the elevated cumulative scores of INQVE, INQVB6 and INQZn. The combination of Alistipes, Roseburia and Barnesiella could moderately predict dietary variety status. CONCLUSION: Higher DVS was correlated with higher microbial diversity and more abundance of some potentially beneficial bacteria but with less some potentially pathogenic bacteria. A high variety dietary, therefore, should be recommended in our daily life.

The more developmental assets, the less internet gaming disorder? Testing the cumulative effect and longitudinal mechanism during the COVID-19 pandemic.

The COVID-19 pandemic has triggered the dramatical development and prosperity of online games, while worldwide people are suffering from it. Considering the high prevalence, serious impacts, and huge development potential of internet gaming disorder (IGD), it is extremely necessary to develop a protective model to prevent and intervene with it among young people. Based on the developmental assets theory, the present study adopted a two-wave longitudinal design to evaluate the cumulative effects of developmental assets on IGD, as well as the underlying mechanisms during this specific period. Data were collected from a sample of 1023 adolescents in Hubei province, Central China through self-report questionnaires. The results indicated that (1) developmental assets were negatively associated with adolescents' IGD concurrently and longitudinally; (2) the overall developmental assets had cumulative effects in linear patterns on adolescents' IGD, concurrently and longitudinally; and (3) internal developmental assets mediated the relationship between external developmental assets and adolescents' IGD longitudinally. Theoretically, the present study supports the developmental assets theory and expands the literature about developmental assets and IGD in younger generations. Practically, the present study provides guidance for prevention and intervention of IGD among adolescents during and after the COVID-19 pandemic. Comprehensive measures should be taken to assist in developing positive internal and external resources to promote youth thriving.

Genetic risk score constructed from common genetic variants is associated with cardiovascular disease risk in type 2 diabetes mellitus.

BACKGROUND: Patients with type 2 diabetes mellitus (T2DM) experience a two-fold increased risk of cardiovascular diseases. Genome-wide association studies (GWAS) have identified T2DM susceptibility genetic variants. Interestingly, the genetic variants associated with cardiovascular disease risk in T2DM Han Chinese remain to be elucidated. The present study aimed to investigate the genetic variants associated with cardiovascular disease risk in T2DM. METHODS: We performed bootstrapping, GWAS and an investigation of genetic variants associated with cardiovascular disease risk in a discovery T2DM cohort and in a replication cohort. The discovery cohort included 326 cardiovascular disease patients and 1209 noncardiovascular disease patients. The replication cohort included 68 cardiovascular disease patients and 317 noncardiovascular disease patients. The main outcome measures were genetic variants for genetic risk score (GRS) in cardiovascular disease risk in T2DM. RESULTS: In total, 35 genetic variants were associated with cardiovascular disease risk. A GRS was generated by combining risk alleles from these variants weighted by their estimated effect sizes (log odds ratio [OR]). T2DM patients with weighted GRS ≥ 12.63 had an approximately 15-fold increase in cardiovascular disease risk (odds ratio = 15.67, 95% confidence interval [CI] = 10.33-24.00) compared to patients with weighted GRS < 10.39. With the addition of weighted GRS, receiver-operating characteristic curves showed that area under the curve with conventional risk factors was improved from 0.719 (95% CI = 0.689-0.750) to 0.888 (95% CI = 0.866-0.910). CONCLUSIONS: These 35 genetic variants are associated with cardiovascular disease risk in T2DM, alone and cumulatively. T2DM patients with higher levels of weighted genetic risk score have higher cardiovascular disease risks.

Cumulative effects of therapies on disability in relapsing multiple sclerosis.

BACKGROUND: Long-term effectiveness of treatment remains a key question in multiple sclerosis (MS) and the cumulative effects of past treatment have not been investigated so far. OBJECTIVE: Explore the relationship between treatment exposure and disability risk in patients with relapsing-remitting multiple sclerosis (RRMS). METHODS: A total of 2285 adult patients from the French nationwide cohort were included. Outcomes were irreversible EDSS4, and conversion to secondary progression of multiple sclerosis (SPMS). Associations between treatments and risk of disability were assessed using a novel weighted cumulative exposure model, assuming a 3-year lag to account for reverse causality. This flexible approach accounts for past exposure in a multivariate Cox proportional hazards model by computing a weight function. RESULTS: At baseline, mean ± standard deviation age of patients was 33.4 ± 8.9 years and 75.0% were women. A 15-year continuous treatment starting 20 years ago was associated with a decrease in risk of 26% for irreversible EDSS4, and 34% for SPMS compared to a 5-year treatment starting 10 years ago. The risk of disability decreased with increasing duration of exposure to disease-modifying treatment (DMT). CONCLUSION: Long-term use of treatments in RRMS has a stronger beneficial cumulative impact than only early uses and delays the occurrence of moderate disability and conversion to SPMS.

Cumulative effect of risk and protective factors on unintentional injury for Chinese rural children: a nested case-control study.

BACKGROUND: Childhood unintentional injuries are the leading cause of death and disability for children. Despite the risk factors that lead to the occurrence of injuries have been identified, the relationship between cumulative effect of risk/protective factors and unintentional injuries is unclear. The aim of this study was to explore the cumulative effect of risk factors as well as protective factors and their interaction on unintentional injury to rural children. METHODS: We used a nested case-control study design from a cohort database. The study comprised 1696 children aged 6 to 14 years. Among them, 424 were cases with unintentional injury and 1272 were their matched control. After controlling for the significant sociodemographic variables, linear and logistic regression analyses were performed. RESULTS: The risk of unintentional injury increased with the increasing number of risk factors - RFI from 1 to 3 (ORRFI(1) = 0.978, 95% CI 0.739-1.296), (ORRFI(2) = 1.720, 95% CI 1.233-2.397), (ORRFI(3) = 5.162, 95% CI 3.129-8.517). PFI (1) was associated with lower risk of injury, but this association was at the edge of significance (p = 0.052). The increased risk in those with PFI (2) was not significant (p = 0.254). The severity of the unintentional injury significantly increased with the increasing number of the risk factors (p < 0.01), and significantly decreased with both the increasing number of protective factors (p = 0.001) and interaction of the risk and protective factors (p < 0.01).The interaction of RFI and PFI could explain 32.2% of the unintentional injury severity. CONCLUSIONS: According to the findings of the present study, cumulative risk factors and protective factors, as well as their interaction were associated with the occurrence and/ or severity of unintentional injury in children.

Assessment on the cumulative effect of pollutants and the evolution of micro-ecosystems in bioretention systems with different media.

Bioretention system is one of the most used green stormwater infrastructures (GSI), and its media is a key factor in reducing runoff water volume and purifying water quality. Many studies have investigated media improvement to enhance the pollutant removal capacity. However, the long-term cumulative effect and microbial effect of pollutants in the modified-media bioretention system is less known. This study investigated the cumulative effect of pollutants and their influence on microbial characteristics in conventional and modified media bioretention system. The addition of modifiers increased the background content of pollutants in the media, and the accumulation of pollutants in planting soil (PS) and bioretention soil mixing + water treatment residuals (BSM+WTR) was relatively higher after the simulated rainfall experiment. The accumulation of pollutants led to a decrease in dehydrogenase activity, and an increase in urease and invertase activities. Ten dominant bacterial species at the phylum level were found in all bioretention systems. The relative abundances of the bacteria with good viability under low nutritional conditions decreased, while the species which could live in the pollutant-rich environment increased. The accumulation of pollutants in the bioretention system led to the extinction of some functional microorganisms. The better the effects of modified media on pollutant removal showed, the more obvious effect on the media micro-ecosystem was. To ensure the long-term efficient and stable operation of the modified-media bioretention system, we recommend balancing the pollutant removal efficiency and cumulative effect in modified-media bioretention systems.

Distribution, bioaccessibility, and health risk assessment of heavy metals in PM2.5 and PM10 during winter heating periods in five types of cities in Northeast China.

PM2.5 and PM10 samples were collected from the outdoor environment of five types of cities (provincial central cities, regional central cities, resource-based cities, agricultural cities, and forested cities) situated in Northeast China. Based on bioaccessibility and respiratory deposition fluxes, health risks of PM2.5- and PM10-bound six heavy metals [HM6: Arsenic (As), Chromium (Cr), Cadmium (Cd), Nickel (Ni), Cobalt (Co), and Lead (Pb)] were studied. Cobalt (Co) and Cr were found to be the most abundantly bioaccessible fraction among HM6 after extraction of simulated lung fluids. After inhalation exposure, among HM6, Co mainly contributed 88.39-93.19% to the non-carcinogenic risk, while Cr account for 82.92-93.72% of cancer risk. The estimated daily intake of bioaccessible HM6 in outdoor environment during the heating period was calculated to be 293.11 ± 121.03, 117.08 ± 32.46, 105.57 ± 32.49, 100.35 ± 25.58 and 83.11 ± 17.64 ng/h for provincial central cities, regional central cities, agricultural city, resource-based cities and forested cities, respectively, for local residents. During the heating period of 180 days, non-carcinogenic risks (As, Cr, Cd, Ni, Co) in outdoor environment of 0.5 residence time were below the safety threshold (HQ < 1). Cancer risks for Cr and Co were above 10-5 in the five types of cities, but in the assumable range (< 10-4). Our study highlighted the wide range of measures needed to cut airborne particles pollution to safer levels.

External Validation of the PHASES Score in Patients with Multiple Intracranial Aneurysms.

OBJECTIVES: This study sought to assess whether the Population, Hypertension, Age, Size, Earlier Subarachnoid Hemorrhage, Site (PHASES) score can do risk stratification of patients with multiple aneurysms (MIAs). MATERIAL AND METHODS: Patients between January 1, 2016 and January 1, 2019 were recruited retrospectively. The PHASES score was applied to assess the theoretical risk of IA rupture. For patients-level analyses, four modes of the application of the score were used: largest IA PHASES score, highest PHASES score, sum PHASES score, and mean PHASES score. RESULTS: A total of 701 patients with 1673 IAs were included in this study. At aneurysm-level analysis, the average PHASES score was 3.0 ± 3.0 points, with 2.8 ± 3.0 points and 4.1 ± 2.9 points in the unruptured and ruptured groups, respectively (p < 0.001). At the patient-level analysis, for the largest IA PHASES score, the areas under the curves (AUC) was 0.572. The discrimination performance of the largest IA PHASES score decreases as IA number increases, with AUCs were 0.597, 0.518, and 0.450 in the 2 IAs, 3 IAs and, 4 or more IAs subgroups, respectively. For highest PHASES score, sum PHASES score, and mean PHASES score, the AUCs were 0.577, 0.599, and 0.619, respectively. CONCLUSIONS: In this study, PHASES score only serve as a weak tool in decision-making settings for MIAs patients; as such, more accurate models should be developed for MIAs patients and the cumulative effect of MIA may should be considered.

Suicide behavior and meteorological characteristics in hot and arid climate.

BACKGROUND: Suicidal behavior is determined by the consequence of an interaction between biological, psychological and sociological factors, as well as between individual and environmental effects. Fluctuations in meteorological factors can modify human behavior and affect suicidal rates. We hypothesize that high temperatures can be associated with an increase rate of suicidal attempts. METHODS: We included all the patients admitted to Soroka University Medical Center (SUMC) due to suicide attempts between the years 2002-2017 and were residents of Southern Israel. We computed two sets of regression models: first, a time stratified case-crossover design to control for seasonality and individual differences. Results are presented as odds ratio (OR) with confidence interval (CI); and then, time-series analyses to calculate the incidence rate ratio (IRR) and the cumulative effect of temperature on the daily incidences of emergency department (ED) admissions after suicide attempts. We stratified the analyses by demographic variables to identify significant individual differences. RESULTS: We identified 3100 attempts, by 2338 patients who lived in Be'er Sheva between 16 and 90 years of age; 421 patients made 2+ attempts. Suicide attempts were associated with a 5 °C increase during the summer season (OR 1.59, 95% CI 1.22-2.08) and a 5 °C increase in all seasons was associated with those who have made multiple attempts (OR 1.18, 95% CI 1.0005-1.38). The cumulative effect of 5 °C increment is associated with more suicide attempts over 2 days (IRR 1.10, 95% CI 0.98; 1.24) and 5 days (IRR 1.04, 95% CI 1.00; 1.08). The associations were greater for patients with psychiatric diagnosis and patients with multiple attempts. In a stratified analysis by individual characteristics we didn't find significant association. CONCLUSION: High temperatures and low amount of precipitations are evidently of great impact on people's susceptibility to suicidal behavior, especially for individuals who have had a prior suicide attempt. Our findings indicate the need for public health attention in the summer when temperature increases precipitously over days, especially for those who have made a prior suicide attempt.

Evaluating the cumulative and time-lag effects of drought on grassland vegetation: A case study in the Chinese Loess Plateau.

The increased frequency of drought events in recent years is known to be responsible for significantly altering plant biodiversity in many of Earth's ecosystems, though the specifics of vegetation-drought interactions, especially the cumulative and time-lag responses, remains unclear. This study aimed to quantitatively investigate how grassland vegetation over the Chinese Loess Plateau (CLP) reacts to drought, specifically the observed cumulative and time-lag effects which are caused, using a combination of the Normalized Difference Vegetation Index (NDVI) and a multiple time-scale drought index (Standardized Precipitation and Evapotranspiration Index, SPEI). Our results revealed that while drought conditions have widespread cumulative impacts on grass growth in the CLP, the time lag effect of drought covered about half of the total area of the CLP. The cumulative effect of drought on grass was found to take place over various time scales, ranging from 5 to 10 months, while the time lag effect occurred within 2-3 months. The different response time of vegetation growth to the cumulative effect of drought in the CLP was found to be highly related to different water conditions. The accumulated months and mean rmax-cum both had a significant negative correlation with the mean annual SPEI (R2 = 0.90, P < 0.001; R2 = 0.70, P < 0.001, respectively). The lagged months and mean rmax-lag were also found to be negatively correlated with the mean annual SPEI (R2 = 0.547, P < 0.05; R2 = 0.785, P < 0.01, respectively).

Satellite detection of cumulative and lagged effects of drought on autumn leaf senescence over the Northern Hemisphere.

Climate change has substantial influences on autumn leaf senescence, that is, the end of the growing season (EOS). Relative to the impacts of temperature and precipitation on EOS, the influence of drought is not well understood, especially considering that there are apparent cumulative and lagged effects of drought on plant growth. Here, we investigated the cumulative and lagged effects of drought (in terms of the Standardized Precipitation-Evapotranspiration Index, SPEI) on EOS derived from the normalized difference vegetation index (NDVI3g) data over the Northern Hemisphere extra-tropical ecosystems (>30°N) during 1982-2015. The cumulative effect was determined by the number of antecedent months at which SPEI showed the maximum correlation with EOS (i.e., Rmax-cml ) while the lag effect was determined by a month during which the maximum correlation between 1-month SPEI and EOS occurred (i.e., Rmax-lag ). We found cumulative effect of drought on EOS for 27.2% and lagged effect for 46.2% of the vegetated land area. For the dominant time scales where the Rmax-cml and Rmax-lag occurred, we observed 1-4 accumulated months for the cumulative effect and 2-6 lagged months for the lagged effect. At the biome level, drought had stronger impacts on EOS in grasslands, savannas, and shrubs than in forests, which may be related to the different root functional traits among vegetation types. Considering hydrological conditions, the mean values of both Rmax-cml and Rmax-lag decreased along the gradients of annual SPEI and its slope, suggesting stronger cumulative and lagged effects in drier regions as well as in areas with decreasing water availability. Furthermore, the average accumulated and lagged months tended to decline along the annual SPEI gradient but increase with increasing annual SPEI. Our results revealed that drought has strong cumulative and lagged effects on autumn phenology, and considering these effects could provide valuable information on the vegetation response to a changing climate.

Dynamic responses of tree-ring growth to multiple dimensions of drought.

Droughts, which are characterized by multiple dimensions including frequency, duration, severity, and onset timing, can impact tree stem radial growth profoundly. Different dimensions of drought influence tree stem radial growth independently or jointly, which makes the development of accurate predictions a formidable challenge. Measurement-based tree-ring data have obvious advantages for studying the drought responses of trees. Here, we explored the use of abundant tree-ring records for quantifying regional response patterns to key dimensions of drought. Specifically, we designed a series of regional-scaled "natural experiments," based on 357 tree-ring chronologies from Southwest USA and location-matched monthly water balance anomalies, to reveal how tree-ring responds to each dimension of drought. Our results showed that tree-ring was affected significantly more by the water balance condition in the current hydrological year than that in the prior hydrological year. Within the current hydrological year, increased drought frequency (number of dry months) and duration (maximum number of consecutive dry months) resulted in "cumulative effects" which amplified the impacts of drought on trees and reduced the drought resistance of trees. Drought events that occurred in the pregrowing seasons strongly affected subsequent tree stem radial growth. Both the onset timing and severity of drought increased "legacy effects" on tree stem radial growth, which reduced the drought resilience of trees. These results indicated that the drought impact on trees is a dynamic process: even when the total water deficits are the same, differences among the drought processes could lead to considerably different responses from trees. This study thus provides a conceptual framework and probabilistic patterns of tree-ring growth response to multiple dimensions of drought regimes, which in turn may have a wide range of implications for predictions, uncertainty assessment, and forest management.

Assessing the cumulative health effect following short term exposure to multiple pollutants: An evaluation of methodological approaches using simulations and real data.

BACKGROUND: Assessment of the cumulative effect of correlated exposures is an open methodological issue in environmental epidemiology. Most previous studies have applied regression models with interaction terms or dimension reduction methods. The combined effect of pollutants has been also evaluated through the use of exposure scores that incorporate weights based on the strength of the component-specific associations with health outcomes. METHODS: We compared three approaches addressing multi-pollutant exposures in epidemiological models: main effects models, the adaptive least absolute shrinkage and selection operator (LASSO) and a weighted exposure score. We assessed the performance of the methods by simulations under various scenarios for the pollutants' correlations. We further applied these methods to time series data from Athens, Greece in 2007-12 to investigate the combined effect of short-term exposure to six regulated pollutants on all-cause and respiratory mortality. RESULTS: The exposure score provided the least biased estimate under all correlation scenarios for both mortality outcomes. The adaptive LASSO performed well in the case of low and medium correlation between exposures while the main effect model resulted in severe bias. In the real data application, the cumulative effect estimate was similar between approaches for all-cause mortality ranging from 0.7% increase per interquartile range (IQR) (score) to 1.1% (main effects), while for respiratory mortality conclusions were contradictive and ranged from - 0.6% (adaptive LASSO) to 2.8% (score). CONCLUSIONS: Τhe use of a weighted exposure score to address cumulative effects of correlated metrics may perform well under different exposure correlation and variability in the health outcomes.