Association of solid fuel use with cognitive function and the modifying role of lifestyle: A nationwide cohort study in China.

BACKGROUND: As opposed to a healthy lifestyle, indoor air pollution from solid fuel use may be harmful for cognitive function. However, the extent to which lifestyle modifies the association between solid fuel use and cognitive function remains unknown. METHODS: A total of 21,008 individuals aged 16 to 92 were enrolled in 2010 and followed up to 2014 in the China Family Panel Studies (CFPS). Cognitive function was assessed using standardized math and word tests in two waves. Solid fuel use at baseline was assessed by self-reporting of firewood, straw, or coal used for cooking. Lifestyle profile was classified into two groups (favorable vs. unfavorable) based on five modifiable lifestyle factors including alcohol drinking, smoking, body mass index, diet, and physical activity. Linear mixed-effects models were employed to assess the association of solid fuel use and lifestyle with cognitive function. The effect modification of lifestyle was analyzed. RESULTS: A total of 49.7% of the study population used solid fuels for cooking and 17.4% had a favorable lifestyle. Solid fuel use was associated with a significant decrease in cognitive function (ß = -0.29, 95% CI: -0.39, -0.19 for math test; ß = -0.62, 95% CI: -0.84, -0.41 for word test). Lifestyle significantly modified this association (p-interaction: 0.006 for math test; 0.016 for word test), with the corresponding association being less pronounced among participants adhering to a favorable lifestyle compared to those with an unfavorable lifestyle. CONCLUSION: A favorable lifestyle may attenuate the adverse association between solid fuel use and cognitive function. Adopting a favorable lifestyle has the potential to mitigate the adverse neurological effects due to indoor air pollution.

Association between reproductive factors with lung cancer incidence and mortality: A pooled analysis of over 308,000 females in the Asia cohort consortium.

Previous studies have investigated the association between reproductive factors and lung cancer risk; however, findings have been inconsistent. In order to assess this association among Asian women, a total of 308,949 female participants from 11 prospective cohorts and four Asian countries (Japan, Korea, China, and Singapore) were included. Cox proportional hazards regression models were used to estimate the hazard ratios (HR) and 95% confidence intervals (CIs). A total of 3,119 primary lung cancer cases and 2247 lung cancer deaths were identified with a mean follow-up of 16.4 years. Parous women had a lower risk of lung cancer incidence and mortality as compared with nulliparous women, with HRs of 0.82 (95% CI = 0.70-0.96) and 0.78 (95% CI = 0.65-0.94). The protective association of parity and lung cancer incidence was greater among ever-smokers (HR = 0.66, 95% CI = 0.49-0.87) than in never-smokers (HR = 0.90, 95% CI = 0.74-1.09) (P-interaction = 0.029). Compared with age at first delivery ≤20 years, older age at first delivery (21-25, ≥26 years) was associated with a lower risk of lung cancer incidence and mortality. Women who ever used hormone replacements had a higher likelihood of developing non-small cell lung cancer (HR = 1.31, 95% CI = 1.02-1.68), compared to those who never used hormone replacements. Future studies are needed to assess the underlying mechanisms, the relationships within these female reproductive factors, and the potential changes in smoking habits over time.

Climate change and population health in Singapore: a systematic review.

Gaseous emissions have contributed to global warming, an increase in the frequency of extreme weather events and poorer air quality. The associated health impacts have been well reported in temperate regions. In Singapore, key climate change adaptation measures and activities include coastal and flood protection, and mitigating heat impacts. We systematically reviewed studies examining climate variability and air quality with population health in Singapore, a tropical city-state in South-East Asia (SEA), with the aim to identify evidence gaps for policymakers. We included 14 studies with respiratory illnesses, cardiovascular outcomes, foodborne disease and dengue. Absolute humidity (3 studies) and rainfall (2 studies) were positively associated with adverse health. Extreme heat (2 studies) was inversely associated with adverse health. The effects of mean ambient temperature and relative humidity on adverse health were inconsistent. Nitrogen dioxide and ozone were positively associated with adverse health. Climate variability and air quality may have disease-specific, differing directions of effect in Singapore. Additional high quality studies are required to strengthen the evidence for policymaking. Research on effective climate action advocacy and adaptation measures for community activities should be strengthened. Funding: There was no funding source for this study.

Determinants of residential greenness and its association with prostate cancer risk: A case-control study in Singapore.

BACKGROUND: Exposure to greenness has been shown to be beneficial to health, but few studies have examined the association between residential greenness and prostate cancer (PCa) risk. Our main objectives were to identify the determinants of residential greenness, and to investigate if residential greenness was associated with PCa risk in Singapore. METHODS: The hospital-based case-control study was conducted between April 2007 and May 2009. The Singapore Prostate Cancer Study (SPCS) comprised 240 prostate cancer cases and 268 controls, whose demographics and residential address were collected using questionnaires. Residential greenness was measured by normalized difference vegetation index (NDVI) around the participants' homes using a buffer size of 1 km. Determinants of NDVI were identified using a multivariable linear regression model. Logistic regression models were used to calculate the odds ratios (ORs) and 95% confidence intervals (CIs) of associations between NDVI and PCa risk, adjusting for potential confounders. RESULTS: Having a BMI within the second quartile, as compared to the lowest quartile, was associated with higher levels of NDVI (ß-coefficient = 0.263; 95% CI = 0.040-0.485) after adjusting for covariates. Additionally, being widowed or separated, as compared to being married, was associated with lower levels of NDVI (ß-coefficient = -0.393; 95% CI = -0.723, -0.063). An interquartile range (IQR) increase in NDVI was positively associated with prostate cancer risk OR = 1.45; 95% CI = 1.02-2.07). Stratified analysis by tumour grade and stage showed that higher NDVI was associated with higher risk of low grade PCa. CONCLUSION: Our findings suggested that residential greenness was associated with higher risk of PCa in Singapore. Future studies on the quality and type of green spaces, as well as other factors of residential greenness, in association with PCa risk should be conducted to better understand this relationship.

Knowledge, attitudes, and perceptions of hidradenitis suppurativa among young adults in Singapore.

Background: The prevalence of hidradenitis suppurativa (HS) is 0.00033% to 4.10% globally. Few epidemiological studies derive from Asia, with social stigmatization postulated to result in under-diagnosis. Objective: This study aimed to assess the self-reported prevalence of HS, and the knowledge, attitudes, and perceptions towards HS among Singaporean young-adults. Methods: A cross-sectional study (n = 158) was conducted by anonymous online questionnaire. The association between demographic factors and risk of potentially undiagnosed HS was evaluated using multivariable logistic regression. Differences between attitude-perception scores by demographic factors and knowledge of HS were tested using two-sample t-tests. Results: The prevalence of diagnosed and potentially undiagnosed HS was 0.63% and 8.9%, respectively. Non-Chinese had significantly higher social attitude-perception scores than Chinese (P = .029). Females had significantly higher social (P = .048) as well as economic and work (P = .037) attitude-perception scores than males. Those with knowledge of HS had significantly higher attitude-perception scores for interpersonal (P = .031) and social (P = .0052) subsections. Limitations: Small sample size, low frequency of HS cases, and self-reported prevalence may not generalize to the broader population in Singapore. Conclusion: Our results suggest a potential underdiagnosis of HS. Non-Chinese stigmatize HS less than Chinese, and females less than males. Individuals with knowledge of HS might be more open to interpersonal and social interactions with HS sufferers.

Exposure to cooking fumes is associated with perturbations in nasal microbiota composition: A pilot study.

Air pollution is one of the leading causes of overall mortality globally. Cooking emissions are a major source of fine particulate matter (PM2.5). However, studies on their potential perturbations on the nasal microbiota as well as their association with respiratory health are lacking. This pilot study aims to assess the environmental air quality among occupational cooks and its associations with nasal microbiota and respiratory symptoms. A total of 20 cooks (exposed) and 20 unexposed controls (mainly office workers), were recruited in Singapore from 2019 to 2021. Information on sociodemographic factors, cooking methods, and self-reported respiratory symptoms were collected using a questionnaire. Personal PM2.5 concentrations and reactive oxygen species (ROS) levels were measured using portable sensors and filter samplers. DNA was extracted from nasal swabs and sequenced using 16s sequencing. Alpha-diversity and beta-diversity were calculated, and between-group variation analysis of species was performed. Multivariable logistic regression was used to estimate odds ratios (ORs) and 95% confidence intervals (CIs) for associations between exposure groups and self-reported respiratory symptoms. Higher daily mean PM2.5 (P = 2 × 10-7) and environmental ROS exposure (P = 3.25 × 10-7) were observed in the exposed group. Alpha diversity of the nasal microbiota between the two groups was not significantly different. However, beta diversity was significantly different (unweighted UniFrac P = 1.11 × 10-5, weighted UniFrac P = 5.42 × 10-6) between the two exposure groups. In addition, certain taxa of bacteria were slightly more abundant in the exposed group compared to unexposed controls. There were no significant associations between the exposure groups and self-reported respiratory symptoms. In summary, the exposed group had higher PM2.5 and ROS exposure levels and altered nasal microbiotas as compared to unexposed controls, though further studies are required to replicate these findings in a larger population.

Association between Vitamin A and E Forms and Prostate Cancer Risk in the Singapore Prostate Cancer Study.

PURPOSE: This study aimed to assess associations between forms of vitamin A and E (both individually and collectively) and the risk of prostate cancer, as well as identify potential effect modifiers. METHODS: Utilizing data from the Singapore Prostate Cancer Study, a hospital-based case-control study, we measured the serum concentrations of 15 different forms of vitamins A and E in 156 prostate cancer patients and 118 control subjects, using a high-performance liquid chromatography technique. These forms included retinol, lutein, zeaxanthin, α-cryptoxanthin, ß-cryptoxanthin, α-carotene, ß-carotene, lycopene, ubiquinone, δ-tocopherol, γ-tocopherol, α-tocopherol, δ-tocotrienol, γ-tocotrienol, and α-tocotrienol. The odds ratio and 95% confidence interval for associations between vitamin A and E and prostate cancer risk were estimated using logistic regression models after adjustment for potential confounders. The analyses were further stratified by smoking and alcohol consumption status. The mixture effect of micronutrient groups was evaluated using weighted quantile sum regression. RESULTS: Higher concentrations of retinol, lutein, α-carotene, ß-carotene, ubiquinone, α-tocopherol, δ-tocotrienol, γ-tocotrienol, and α-tocotrienol were significantly and positively associated with overall prostate cancer risk. Among ever-smokers, associations were stronger for lutein, ß-cryptoxanthin and ß-carotene compared with never-smokers. Among regular alcohol drinkers, associations were stronger for lutein, ß-cryptoxanthin, ubiquinone, γ-tocotrienol and α-tocotrienol compared with non-regular alcohol drinkers. Retinol and α-tocotrienol contributed most to the group indices 'vitamin A and provitamin A carotenoids' and 'vitamin E', respectively. CONCLUSIONS: Several serum vitamin A and E forms were associated with prostate cancer risk, with significant effect modification by smoking and alcohol consumption status. Our findings shed light on prostate cancer etiology.

Genome-wide association study of lung adenocarcinoma in East Asia and comparison with a European population.

Lung adenocarcinoma is the most common type of lung cancer. Known risk variants explain only a small fraction of lung adenocarcinoma heritability. Here, we conducted a two-stage genome-wide association study of lung adenocarcinoma of East Asian ancestry (21,658 cases and 150,676 controls; 54.5% never-smokers) and identified 12 novel susceptibility variants, bringing the total number to 28 at 25 independent loci. Transcriptome-wide association analyses together with colocalization studies using a Taiwanese lung expression quantitative trait loci dataset (n = 115) identified novel candidate genes, including FADS1 at 11q12 and ELF5 at 11p13. In a multi-ancestry meta-analysis of East Asian and European studies, four loci were identified at 2p11, 4q32, 16q23, and 18q12. At the same time, most of our findings in East Asian populations showed no evidence of association in European populations. In our studies drawn from East Asian populations, a polygenic risk score based on the 25 loci had a stronger association in never-smokers vs. individuals with a history of smoking (Pinteraction = 0.0058). These findings provide new insights into the etiology of lung adenocarcinoma in individuals from East Asian populations, which could be important in developing translational applications.

Second-hand smoke and fine particulate matter exposures among multi-unit housing residents in Singapore: A pilot study.

Globally, approximately 1.2 million deaths among non-smokers are attributed to second-hand smoke (SHS) per year. Multi-unit housing is becoming the common type of residential dwelling in developed cities and the issue of neighbour SHS is of rising concern especially as 'Work From Home' became the norm during and post COVID-19 pandemic. The objective of this pilot study is to measure and compare the air quality of households that are exposed to SHS and unexposed households among smoking and non-smoking households in Singapore. A total of 27 households were recruited from April to August 2021. Households were categorized into smoking households with neighbour SHS, smoking households without neighbour SHS, non-smoking households with neighbour SHS, and non-smoking household without neighbour SHS. Air quality of the households was measured using calibrated particulate matter (PM2.5) sensors for 7-16 days. Socio-demographic information and self-reported respiratory health were collected. Regression models were used to identify predictors associated with household PM2.5 concentrations and respiratory health. Mean PM2.5 concentration was significantly higher among non-smoking households with neighbour SHS (n = 5, mean = 22.2, IQR = 12.7) than in non-smoking household without neighbour SHS (n = 2, mean = 4.1, IQR = 5.8). Smoking activity at enclosed areas in homes had the lowest PM2.5 concentration (n = 7 mean = 15.9, IQR = 11.0) among the three smoking locations. Exposure to higher household PM2.5 concentration was found to be associated with poorer respiratory health. A 'smoke-free residential building' policy is recommended to tackle the issue of rising neighbour SHS complaints and health concerns in densely populated multi-unit housing in Singapore. Public education campaigns should encourage smokers to smoke away from the home to minimize SHS exposure in household members.

Dietary factors and the risk of lung cancer by epidermal growth factor receptor mutation status and histological subtypes.

Background: Previous studies have reported differential associations of certain dietary factors such as soy consumption by epidermal growth factor receptor mutant (EGFR +) subtype of non-small cell lung cancer (NSCLC). However, whether the other dietary factors including meat, fruits, and vegetables have differential risks on different histological and molecular subtypes of lung cancer remains unclear. Therefore, we conducted a case-control study to evaluate these associations. Methods: A total of 3,170 cases and 4,238 controls from three different studies (Genes and Environment in Lung Cancer Study, Lung Cancer Consortium Singapore Study, and Multi-ethnic Cohort Study) were included. Information on demographics, lifestyle, and dietary consumption was obtained using questionnaires. Diet was assessed by using the number of standard servings of each item consumed per week. Multivariable logistic regression was used to estimate odds ratios (ORs) and 95% confidence intervals (CIs) for the association between meat, vegetables, and fruits consumption with lung cancer risk after adjusting for potential confounders. Results: We identified a significant inverse association between higher consumption of fruits and the risk of lung cancer (2nd tertile: OR = 0.54, 95%CI = 0.46-0.65; 3rd tertile: OR = 0.77, 95%CI = 0.65-0.91), compared with the lower (1st tertile) consumption of fruits. Higher vegetable consumption was significantly associated with a lower risk of EGFR + lung cancer (OR = 0.69, 95% CI = 0.54-0.88), however, this association was not significant among EGFR wild-type (-) lung cancer. Conversely, higher consumption of total meat (OR = 2.10, 95%CI = 1.58-2.79) was significantly associated with higher lung cancer risk, as compared with the lower consumption group. Conclusions: Differential associations between vegetable consumption with EGFR mutation status in NSCLC were found. Further prospective studies are warranted to assess this association and elucidate the biological mechanisms.

Overall and cause-specific mortality rates among men and women with high exposure to indoor air pollution from the use of smoky and smokeless coal: a cohort study in Xuanwei, China.

OBJECTIVES: Never-smoking women in Xuanwei (XW), China, have some of the highest lung cancer rates in the country. This has been attributed to the combustion of smoky coal used for indoor cooking and heating. The aim of this study was to evaluate the spectrum of cause-specific mortality in this unique population, including among those who use smokeless coal, considered 'cleaner' coal in XW, as this has not been well-characterised. DESIGN: Cohort study. SETTING: XW, a rural region of China where residents routinely burn coal for indoor cooking and heating. PARTICIPANTS: Age-adjusted, cause-specific mortality rates between 1976 and 2011 were calculated and compared among lifetime smoky and smokeless coal users in a cohort of 42 420 men and women from XW. Mortality rates for XW women were compared with those for a cohort of predominately never-smoking women in Shanghai. RESULTS: Mortality in smoky coal users was driven by cancer (41%), with lung cancer accounting for 88% of cancer deaths. In contrast, cardiovascular disease (CVD) accounted for 32% of deaths among smokeless coal users, with 7% of deaths from cancer. Total cancer mortality was four times higher among smoky coal users relative to smokeless coal users, particularly for lung cancer (standardised rate ratio (SRR)=17.6). Smokeless coal users had higher mortality rates of CVD (SRR=2.9) and pneumonia (SRR=2.5) compared with smoky coal users. These patterns were similar in men and women, even though XW women rarely smoked cigarettes. Women in XW, regardless of coal type used, had over a threefold higher rate of overall mortality, and most cause-specific outcomes were elevated compared with women in Shanghai. CONCLUSIONS: Cause-specific mortality burden differs in XW based on the lifetime use of different coal types. These observations provide evidence that eliminating all coal use for indoor cooking and heating is an important next step in improving public health particularly in developing countries.

Air quality and the risk of out-of-hospital cardiac arrest in Singapore (PAROS): a time series analysis.

BACKGROUND: Previous studies have reported positive associations between out-of-hospital cardiac arrest (OHCA) and air pollutant concentrations, but there are inconsistencies across studies. We aimed to investigate the association between pollutant concentrations and the risk of OHCA in Singapore. METHODS: We did a time series analysis of all cases of OHCA in Singapore reported between July 1, 2010, and Dec 31, 2018, to the Pan-Asian Resuscitation Outcomes Study (PAROS), a prospective, population-based registry. Using multivariable fractional polynomial modelling, we investigated the immediate (day 0) and lagged (up to 5 days after exposure) association between 10 µg/m3 increases in concentrations of particulate matter with a diameter of 2·5 µm or smaller (PM2·5), particulate matter with a diameter of 10 µm or smaller (PM10), ozone (O3), nitrogen dioxide (NO2), and sulphur dioxide (SO2) and 1 mg/m3 increase in carbon monoxide (CO) and relative risk (RR) of OHCA. FINDINGS: We extracted data for 18 131 cases of OHCA. The median age of this cohort of cases was 65 years (IQR 56-80), 6484 (35·8%) were female, 11 647 (64·2%) were male, 12 270 (67·7%) were Chinese, 2873 (15·8%) were Malay, and 2010 (11·1%) were Indian. Every 10 µg/m3 increase in PM2·5 was associated with increased risk of OHCA (RR 1·022 [95% 1·002-1·043]) over the next 2 days, which decreased over the subsequent 3 days (3-5 days after exposure; 0·976 [0·955-0·998]). For PM10, O3, NO2, and SO2, we did not observe any associations between increased concentration and risk of OHCA on day 0 or cumulative risk over time (ie, at 0-1 days, 0-2 days, 0-3 days, 0-4 days, 0-5 days, and 3-5 days after exposure). For CO, we observed a cumulative decreased risk of OHCA across 0-5 days after exposure (0·876 [0·770-0·997]) and at days 3-5 after exposure (0·810 [0·690-0·949]). We observed effect modification of the association between increasing PM2·5 concentration and OHCA 0-2 days after exposure by cardiac arrest rhythm (non-shockable 1·027 [1·004-1·050] vs shockable 1·002 [0·956-1·051]) and location of OHCA (at home: 1·033 [1·008-1·057] vs not at home 0·955 [0·957-1·035]). In hypothetical modelling, the number of OHCA events associated with PM2·5 could be reduced by 8% with a 1 µg/m3 decrease in PM2·5 concentrations and by 30% with a 3 µg/m3 decrease in PM2·5 concentrations. INTERPRETATION: Increases in PM2·5 concentration were associated with an initial increased risk of OHCA and a subsequent reduced risk from 3-5 days after exposure, suggesting a short-term harvesting effect. A decrease in PM2·5 concentrations could reduce population demand for emergency health services. FUNDING: National Medical Research Council, Singapore, under the Clinician Scientist Award, Singapore and the Singapore Translational Research Investigator Award (MOH-000982-01).

Association between diesel exhaust exposure and mitochondrial DNA methylation.

OBJECTIVES: Diesel exhaust is an established human carcinogen, however the mechanisms by which it leads to cancer development are not fully understood. Mitochondrial dysfunction is an established contributor to carcinogenesis. Recent studies have improved our understanding of the role played by epigenetic modifications in the mitochondrial genome on tumorigenesis. In this study, we aim to evaluate the association between diesel engine exhaust (DEE) exposure with mitochondrial DNA (mtDNA) methylation levels in workers exposed to DEE. METHODS: The study population consisted of 53 male workers employed at a diesel engine manufacturing facility in Northern China who were routinely exposed to diesel exhaust in their occupational setting, as well as 55 unexposed male control workers from other unrelated factories in the same geographic area. Exposure to DEE, elemental carbon, organic carbon, and particulate matter (PM2.5) were assessed. mtDNA methylation for CpG sites (CpGs) from seven mitochondrial genes (D-Loop, MT-RNR1, MT-CO2, MT-CO3, MT-ATP6, MT-ATP8, MT-ND5) was measured in blood samples. Linear regression models were used to estimate the associations between DEE, elemental carbon, organic carbon and PM2.5 exposures with mtDNA methylation levels, adjusting for potential confounders. RESULTS: DEE exposure was associated with decreased MT-ATP6 (difference = -35.6%, P-value = 0.019) and MT-ATP8 methylation (difference = -30%, P-value = 0.029) compared to unexposed controls. Exposures to elemental carbon, organic carbon, and PM2.5 were also significantly and inversely associated with methylation in MT-ATP6 and MT-ATP8 genes (all P-values < 0.05). CONCLUSIONS: Our findings suggest that DEE exposure perturbs mtDNA methylation, which may be of importance for tumorigenesis.

Secondhand smoke in the densely populated urban setting: A cross-sectional survey of exposure, knowledge, attitudes, and respiratory symptoms.

Secondhand smoke (SHS) remains a common health threat in densely populated, urban settings. We estimated the prevalence of exposure and associated respiratory symptoms, knowledge, attitudes, and behaviors in a multi-ethnic, weighted sample of Singapore residents using a cross-sectional survey of 1806 adults. We weighted data to match the national population in terms of gender, ethnicity, and education level and analyzed data using descriptive statistics, bivariate analyses, multiple linear and logistic regressions, and a multinomial logistic regression model. About 88% of respondents reported regular SHS exposure. Nearly 57% reported exposure to neighbors' SHS at home. Respiratory symptoms were reported by 32.5% and significantly associated with exposure to daily (AOR = 2.63, 95% CI = 1.62-4.36), non-daily (AOR = 1.75, 95% CI = 1.14-2.77), and neighbors' (AOR = 1.37, 95% CI = 1.07-1.76) SHS. More knowledge of SHS was associated with male gender (ß = 0.28, p = 0.0009) and higher household income (linear trend; p = 0.0400). More negative attitudes to SHS were associated with older age (linear trend; p < 0.0001). Engaging in behaviors to avoid SHS was associated with a more negative attitude to SHS (AOR = 1.09-1.23). SHS exposure is common in Singapore's densely populated setting and associated with respiratory symptoms, even if exposure is non-daily or from neighboring homes.

Change of air quality knowledge, perceptions, attitudes, and practices during and post-wildfires in the United States.

Amid worsening climate change, the recurrent wildfires have substantially worsened air quality in the Western United States (U.S.). Understanding the knowledge, attitudes, perception, and practices (KAPP) over time in response to natural disasters such as wildfires is crucial for public health interventions and disaster preparedness. This is the first study to investigate the change in air quality KAPP over time in response to natural disasters. Previous studies have only assessed KAPP at a fixed time point. Using a two-wave panel survey (during and post-wildfires), we assessed the association between KAPP and respiratory health indicators as well as the changes over time in 212 participants in the U.S. Between the two waves, we found a significant 8% increase in knowledge, which was mainly driven by participants in areas unaffected by the wildfires. In addition, we found differential associations between KAPP and respiratory health indicators between areas affected and unaffected by the wildfires. These findings suggest that experiencing wildfires may affect KAPP and more longitudinal studies are warranted, particularly during periodic air quality crises.

Association of ambient air pollution with risk of hemorrhagic stroke: A time-stratified case crossover analysis of the Singapore stroke registry.

BACKGROUND: Haemorrhagic stroke (HS) is a major cause of mortality and disability. Previous studies reported inconsistent associations between ambient air pollutants and HS risk. OBJECTIVE: We evaluated the association between air pollutant exposure and the risk of HS in a cosmopolitan city in the tropics. METHODS: We performed a nationwide, population-based, time-stratified case-crossover analysis on all HS cases reported to the Singapore Stroke Registry from 2009 to 2018 (n = 12,636). We estimated the risk of HS across tertiles of air pollutant concentrations in conditional Poisson models, adjusting for meteorological confounders. We stratified our analysis by age, atrial fibrillation and smoking status, and investigated the lagged effects of each pollutant on the risk of HS up to 5 days. RESULTS: All 12,636 episodes of HS were included. The median (1st-to 3rd-quartile) daily pollutant levels from 22 remote stations deployed across the island were as follows: (PM2.5 = 15.9 (12.7-20.5), PM10 = 27.3 (22.7-33.4), O3 = 22.5 (17.3-29.8), NO2 = 23.3 (18.8-28.4), SO2 = 10.2 (5.6-14.4), CO = 0.5 (0.5-0.6). The median (1st-to 3rd-quartile) temperature (°C) was 27.9 (27.1-28.7), that of relative humidity (%) was 79.4 (75.6-83.2), and that of total rainfall (mm) was 0.0 (0.0-4.2). Higher levels of CO were significantly associated with an increased risk of HS (3rd tertile vs 1st tertile: Incidence Rate Ratio (IRR) = 1.06, 95% CI = 1.01-1.12). The increased risk of HS due to CO persisted for at least 5 days after exposure. Individuals under 65 years old and non-smokers had a higher risk of HS when exposed to CO. O3 was associated with increased risk of HS up to 5 days (3rd tertile vs 1st tertile: IRRday 1 = 1.07, 95% CI = 1.02-1.12; IRRday 5 = 1.07, 95% CI = 1.02-1.13). CONCLUSION: Short-term exposure to ambient CO levels was associated with an increased risk of HS. A reduction in CO emissions may reduce the burden of HS in the population.

Development and validation of a new scale to assess air quality knowledge (AQIQ).

BACKGROUND: Air pollution is a leading public health concern around the world. Assessing the public's knowledge about air quality is critical to calibrate public health interventions. However, previous efforts to measure knowledge about air quality (AQIQ) have not relied on consistent and validated measures, thus precluding cross-country comparisons. We aimed to develop a robust scale to assess AQIQ and tested it in multiple countries. METHODS: To evaluate the psychometric properties and select the best performing items out of 10 AQIQ questions, we used methods from classical test theory and item response theory. We evaluated the scales using several scalability measures, including the Kuder-Richardson Formula 20 (KR-20), Loevinger's H, as well as trace lines. Volunteers from the United States (US, n = 400), India (n = 403), and China (n = 443) were recruited to validate the scale. Multiple linear regression was used to estimate the association between demographic factors and AQIQ. RESULTS: We found that participants from India had the highest AQIQ. In addition, not all questions performed well in each country. The scale was pruned and shorter subscales were validated. In the US, we obtained a 4-item scale (KR20 = 0.53, Loevinger's H = 0.34). In India, we obtained a 6-item scale (KR20 = 0.56; Loevinger's H = 0.48 for just 2 items). In China, we obtained a 5-item scale (KR20 = 0.39; Loevinger's H = 0.41 for just 2 items). Compared to the 10-item scale, the pruned scales showed stronger associations between measures of socioeconomic status and AQIQ. The results were robust to the scale used. CONCLUSIONS: Overall, general knowledge questions measured AQIQ more effectively in the US and India whereas knowledge of the air quality index better measured AQIQ in China. The findings suggest that careful measurement and validation are essential to develop knowledge scales for use in public health and environmental research.

Vitamin E Intake and Risk of Prostate Cancer: A Meta-Analysis.

Vitamin E is a group of antioxidative tocopherols and tocotrienols that play a potential role in chemoprevention. Studies investigating the association between vitamin E and prostate cancer risk have been conflicting. We identified observational and interventional studies examining the association between vitamin E intake and prostate cancer risk from PubMed, EMBASE and the Cochrane Library. A random-effects model was used to perform a meta-analysis and estimate relative risks (RRs) and the corresponding 95% confidence intervals (CIs) of prostate cancer risk according to vitamin E intake. Subgroup analyses were conducted by study design, sample size, study population characteristics, geographical region, and dose of vitamin E intake. The association between dietary (RR = 0.97; 95% CI = 0.92-1.02) and supplemental (RR = 0.99; 95% CI = 0.94-1.04) vitamin E intake on prostate cancer risk was non-significant. In subgroup analyses, supplemental vitamin E was significantly associated with reduced prostate cancer risk in studies in Europe (RR = 0.81, 95% CI = 0.69-0.97). Overall, this meta-analysis demonstrates little evidence for a beneficial effect of vitamin E intake on prostate cancer risk but suggests that there may be some conditions in which supplements could confer a protective effect on prostate cancer risk.

Association between family history and lung cancer risk among Chinese women in Singapore.

Risk factors of lung cancer unrelated to smoking are not well-studied, especially among women. Family history has been shown to play a role in predisposing individuals to lung cancer, but this relationship has not been investigated in the Southeast Asian population. A total of 1159 women were recruited in a case-control study conducted in public hospitals in Singapore from 2005 to 2008. After excluding participants with incomplete family history information, 374 cases and 785 controls remained in the final analysis. Adjusted odds ratios (aORs) and 95% confidence intervals (CIs) were calculated using logistic regression, adjusting for potential confounders. Overall, family history of lung cancer was associated with a higher risk for lung cancer (aOR 2.08, 95% CI 1.25-3.47). When stratified by smoking status, a significant association was observed among never-smokers (aOR 2.78, 95% CI 1.57-4.90). Further stratification by fruit consumption identified a significant association between family history of lung cancer and higher risk of lung cancer among never-smokers who had low fruit consumption (aOR 3.09, 95% CI 1.37-7.01). Our findings suggest that family history of lung cancer is a significant risk factor for lung cancer in Singaporean Chinese women, especially among never-smokers.