scholarly journals The Search for Non-Linear Exposure-Response Relationships at Ambient Levels in Environmental Epidemiology

2005 ◽  
Vol 3 (1) ◽  
pp. nonlin.003.01.0 ◽  
Author(s):  
Morton Lippmann
Keyword(s):  
Environmental Epidemiology ◽  
Exposure Response ◽  
Non Linear ◽  
Ambient Levels

scholarly journals 757Using smartphone technology to characterise associations between respiratory symptoms and pollen

2021 ◽  
Vol 50 (Supplement_1) ◽  
Author(s):  
Penelope Jones ◽  
Fay Johnston ◽  
Iain Koolhof ◽  
Antonio Gasparrini ◽  
Amanda Wheeler ◽  
...  
Keyword(s):  
Air Pollution ◽  
Respiratory Symptoms ◽  
Airborne Pollen ◽  
Environmental Epidemiology ◽  
Particulate Pollution ◽  
Exposure Response ◽  
Pollen Concentrations ◽  
Non Linear ◽  
Smartphone Technology ◽  
Total Pollen

Abstract Background Pollen is a well-established trigger of asthma and allergic rhinoconjunctivitis, yet key gaps in our understanding remain. These include knowledge of concentration thresholds for symptoms, exposure-response associations through time, and the potential for interactions with other environmental stressors such as air pollution. Smartphone technology offers an opportunity to address these challenges using large datasets that capture individual symptoms in real time. Methods We analysed 44,820 symptom reports logged by 2,272 users of the AirRater app over four years to evaluate associations between daily respiratory symptoms and atmospheric concentrations of pollen in Tasmania, Australia. We used case time series, a novel methodology developed for app-sourced data. We adjusted for seasonality and meteorology and tested for interactions with particulate pollution (PM2.5). Results There was a non-linear association between pollen concentrations and respiratory symptoms for up to three days following exposure. Risk ratios (RR) were greatest on the same day, for total pollen increased steeply to a RR of 1.31 (95% CI: 1.26-1.37) at a concentration of 50 grains/m3 before plateauing. Associations with individual pollen taxa showed similar non-linear trends. There was an interaction with PM2.5, with effect estimates significantly higher when PM2.5 was >50 µg/m3 (p for interaction < 0.001). Conclusions The association between respiratory symptoms and airborne pollen was non-linear, greatest in magnitude on the day of exposure, and synergistic with air pollution. Key messages Smartphone symptom tracking offers a useful means of assessing dose-response relationships in environmental epidemiology.

scholarly journals 1302Potential exposure-response relationships between vitamin D and cognitive performance in middle to older-aged adults

2021 ◽  
Vol 50 (Supplement_1) ◽  
Author(s):  
Janis Harse ◽  
Kun Zhu ◽  
Romola Bucks ◽  
Michael Hunter ◽  
Ee Mun Lim ◽  
...  
Keyword(s):  
Vitamin D ◽  
Cognitive Performance ◽  
Serum Levels ◽  
Vitamin D Status ◽  
Linear Pattern ◽  
Hydroxyvitamin D ◽  
Exposure Response ◽  
Non Linear ◽  
Global Cognition ◽  
And Performance

Abstract Background Low vitamin D status is consistently associated with poorer global cognition in older adults, particularly women, but findings in relation to higher status are unclear. A better understanding of the relationship across the range is required. Methods We investigated patterns of association between serum levels of 25-hydroxyvitamin D (25OHD), the standard measure of vitamin D status, and cognitive performance in 4872 middle to older-aged adults from the Busselton Healthy Ageing Study. Global cognition and performance in domains of attention, memory, and executive function were modelled using linear regression and restricted cubic splines, while controlling for demographic, lifestyle, and health factors. Results Mean (SD) serum 25OHD levels were 78 (24) nM/L for women and 87 (25) nM/L for men. Positive, linear patterns for global cognition in women (p = 0.023) and attention accuracy in men (p = 0.022) suggested cognitive performance improved throughout the range. A non-linear pattern for attention accuracy in women suggested performance improved up to 25OHD levels of approximately 80 nM/L and then plateaued (p = 0.035). In men, negative patterns for semantic verbal fluency (linear, p = 0.025) and global cognition (non-linear, p = 0.015) suggested performance declined as 25OHD levels increased. Conclusions Effects were small and patterns of association were inconsistent for men and women and across domains. However, the positive patterns identified for women, particularly in relation to attention accuracy, have biological plausibility as early, exposure-response relationships.

scholarly journals Occupational noise exposure and the prevalence of dyslipidemia in a cross-sectional study

2021 ◽  
Vol 21 (1) ◽  
Author(s):  
Kun Zhang ◽  
Feng Jiang ◽  
Haibin Luo ◽  
Fangwei Liu
Keyword(s):  
Noise Exposure ◽  
Cross Sectional Study ◽  
Confounding Factors ◽  
Occupational Noise ◽  
Cross Sectional ◽  
Occupational Noise Exposure ◽  
Exposure Response ◽  
Exposed Workers ◽  
Non Linear ◽  
Physical Examinations

Abstract Background Occupational noise exposure was related to cardiovascular disease, of which dyslipidemia was an important inducement. This study investigated the relationship between occupational noise exposure and dyslipidemia. Methods Four hundred ninety-two occupational noise-exposed workers and 664 non-exposed workers were recruited to conduct environmental noise tests and personal occupational physical examinations. A lasso-logistic regression model was used to estimate the relative risk of dyslipidemia. A restricted cubic spline was used to estimate the association between noise exposure years and dyslipidemia after adjusting for potential confounding factors. Results A crude association was observed between the occupational noise exposure (75–85 dB(A)) and dyslipidemia. After adjusting for confounding factors, there was a non-linear relationship between noise exposure years and dyslipidemia (P for non-linearity =0.01). Workers exposed to 75–85 dB(A) for 11 to 24.5 years had a higher risk of dyslipidemia than non-exposed workers. Conclusions A positive and non-linear exposure-response relationship was found in workers exposed to 75–85 dB(A) whose exposure years were between 11 and 24.5. Workers had the highest risk of dyslipidemia when exposed for 13.5 years.

scholarly journals The Comparison of Alternative Smoothing Methods for Fitting Non-Linear Exposure-Response Relationships with Cox Models in a Simulation Study

2009 ◽  
Vol 5 (1) ◽  
Author(s):  
Usha S Govindarajulu ◽  
Elizabeth J Malloy ◽  
Bhaswati Ganguli ◽  
Donna Spiegelman ◽  
Ellen A Eisen
Keyword(s):  
Simulation Study ◽  
Cox Models ◽  
Smoothing Methods ◽  
Exposure Response ◽  
Non Linear

scholarly journals Combining Ensemble Learning Techniques and G-Computation to Investigate Chemical Mixtures in Environmental Epidemiology Studies

2017 ◽  
Author(s):  
Youssef Oulhote ◽  
Marie-Abele Bind ◽  
Brent Coull ◽  
Chirag J Patel ◽  
Philippe Grandjean
Keyword(s):  
Ensemble Learning ◽  
Environmental Epidemiology ◽  
Additive Models ◽  
Response Relationship ◽  
Chemical Mixtures ◽  
Exposure Response ◽  
Learning Techniques ◽  
Extreme Gradient Boosting ◽  
Epidemiology Studies ◽  
Correlated Exposures

ABSTRACTBackgroundAlthough biomonitoring studies demonstrate that the general population experiences exposure to multiple chemicals, most environmental epidemiology studies consider each chemical separately when assessing adverse effects of environmental exposures. Hence, the critical need for novel approaches to handle multiple correlated exposures.MethodsWe propose a novel approach using the G-formula, a maximum likelihood-based substitution estimator, combined with an ensemble learning technique (i.e. SuperLearner) to infer causal effect estimates for a multi-pollutant mixture. We simulated four continuous outcomes from real data on 5 correlated exposures under four exposure-response relationships with increasing complexity and 500 replications. The first simulated exposure-response was generated as a linear function depending on two exposures; the second was based on a univariate nonlinear exposure-response relationship; the third was generated as a linear exposure-response relationship depending on two exposures and their interaction; the fourth simulation was based on a non-linear exposure-response relationship with an effect modification by sex and a linear relationship with a second exposure. We assessed the method based on its predictive performance (Minimum Square error [MSE]), its ability to detect the true predictors and interactions (i.e. false discovery proportion, sensitivity), and its bias. We compared the method with generalized linear and additive models, elastic net, random forests, and Extreme gradient boosting. Finally, we reconstructed the exposure-response relationships and developed a toolbox for interactions visualization using individual conditional expectations.ResultsThe proposed method yielded the best average MSE across all the scenarios, and was therefore able to adapt to the true underlying structure of the data. The method succeeded to detect the true predictors and interactions, and was less biased in all the scenarios. Finally, we could correctly reconstruct the exposure-response relationships in all the simulations.ConclusionsThis is the first approach combining ensemble learning techniques and causal inference to unravel the effects of chemical mixtures and their interactions in epidemiological studies. Additional developments including high dimensional exposure data, and testing for detection of low to moderate associations will be carried out in future developments.

Measurement error in environmental epidemiology and the shape of exposure-response curves

2011 ◽  
Vol 41 (8) ◽  
pp. 651-671 ◽  
Author(s):  
Lorenz R. Rhomberg ◽  
Juhi K. Chandalia ◽  
Christopher M. Long ◽  
Julie E. Goodman
Keyword(s):  
Measurement Error ◽  
Environmental Epidemiology ◽  
Response Curves ◽  
Exposure Response

B. The Non-Linear Calculations for Pulsating Stars

1967 ◽  
Vol 28 ◽  
pp. 105-176
Author(s):  
Robert F. Christy
Keyword(s):  
Major Part ◽  
Afternoon Session ◽  
Discussion Session ◽  
Pulsating Stars ◽  
Fourth Symposium ◽  
Non Linear ◽  
Considerable Discussion ◽  
Informal Approach ◽  
Preceding Session

(Ed. note: The custom in these Symposia has been to have a summary-introductory presentation which lasts about 1 to 1.5 hours, during which discussion from the floor is minor and usually directed at technical clarification. The remainder of the session is then devoted to discussion of the whole subject, oriented around the summary-introduction. The preceding session, I-A, at Nice, followed this pattern. Christy suggested that we might experiment in his presentation with a much more informal approach, allowing considerable discussion of the points raised in the summary-introduction during its presentation, with perhaps the entire morning spent in this way, reserving the afternoon session for discussion only. At Varenna, in the Fourth Symposium, several of the summaryintroductory papers presented from the astronomical viewpoint had been so full of concepts unfamiliar to a number of the aerodynamicists-physicists present, that a major part of the following discussion session had been devoted to simply clarifying concepts and then repeating a considerable amount of what had been summarized. So, always looking for alternatives which help to increase the understanding between the different disciplines by introducing clarification of concept as expeditiously as possible, we tried Christy's suggestion. Thus you will find the pattern of the following different from that in session I-A. I am much indebted to Christy for extensive collaboration in editing the resulting combined presentation and discussion. As always, however, I have taken upon myself the responsibility for the final editing, and so all shortcomings are on my head.)

A decomposition method in non-linear programmm

Optimization ◽  
1975 ◽  
Vol 6 (4) ◽  
pp. 549-559
Author(s):  
L. Gerencsér
Keyword(s):  
Decomposition Method ◽  
Non Linear
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