| 51. |
- Lampa, Erik, et al.
(författare)
-
The identification of complex interactions in epidemiology and toxicology : a simulation study of Boosted Regression Trees
- 2014
-
Ingår i: Environmental Health. - 1476-069X. ; 13, s. 57-
-
Tidskriftsartikel (refereegranskat)abstract
- Background: There is a need to evaluate complex interaction effects on human health, such as those induced by mixtures of environmental contaminants. The usual approach is to formulate an additive statistical model and check for departures using product terms between the variables of interest. In this paper, we present an approach to search for interaction effects among several variables using boosted regression trees. Methods: We simulate a continuous outcome from real data on 27 environmental contaminants, some of which are correlated, and test the method's ability to uncover the simulated interactions. The simulated outcome contains one four-way interaction, one non-linear effect and one interaction between a continuous variable and a binary variable. Four scenarios reflecting different strengths of association are simulated. We illustrate the method using real data. Results: The method succeeded in identifying the true interactions in all scenarios except where the association was weakest. Some spurious interactions were also found, however. The method was also capable to identify interactions in the real data set. Conclusions: We conclude that boosted regression trees can be used to uncover complex interaction effects in epidemiological studies.
|
|
| 52. |
- Lee, Duk-Hee, et al.
(författare)
-
Associations of persistent organic pollutants with abdominal obesity in the elderly : The Prospective Investigation of the Vasculature in Uppsala Seniors (PIVUS) study
- 2012
-
Ingår i: Environment International. - : Elsevier. - 0160-4120 .- 1873-6750. ; 40, s. 170-178
-
Tidskriftsartikel (refereegranskat)abstract
- Objectives: In animal experiments, persistent organic pollutants (POPs) have induced visceral obesity. To address this possibility in humans, we evaluated associations between POPs and abdominal obesity both cross-sectionally and prospectively.Methods: Twenty-one plasma POPs (16 polychlorinated biphenyl (PCB) congeners, 3 organochlorine (OC) pesticides, 1 brominated diphenyl ether (BDE), and 1 dioxin) were measured at baseline in 970 participants aged 70 years of the Prospective Investigation of the Vasculature in Uppsala Seniors (PIVUS), with prospective analyses in 511 participants re-examined after 5 years. Abdominal obesity was defined by an increased waist circumference.Results: In the cross-sectional analyses, concentrations of the less chlorinated PCBs, OC pesticides such as p,p'-DDE and dioxin had adjusted odds ratios of 2 to 3 for abdominal obesity. Many relations had inverted U-shapes rather than being linear, particularly in women. In contrast, concentrations of highly chlorinated PCBs were strongly inversely associated with abdominal obesity. In a single model including summary measures of the less chlorinated PCBs, highly chlorinated PCBs, and OC pesticides, both the positive associations and inverse associations strengthened. Similar but somewhat weaker associations were seen between POPs and risk of development of abdominal obesity in the prospective analyses.Conclusion: Using both a cross-sectional and a prospective design, low-dose exposure to less chlorinated PCBs, p,p'-DDE, and dioxin, were associated with existence or development of abdominal obesity, while highly chlorinated PCBs had an opposite association in an elderly population, despite the previous observation of higher incident diabetes associated with these same PCBs.
|
|
| 53. |
- Lee, Duk-Hee, et al.
(författare)
-
Background exposure to persistent organic pollutants predicts stroke in the elderly
- 2012
-
Ingår i: Environment International. - : Elsevier BV. - 0160-4120 .- 1873-6750. ; 47, s. 115-120
-
Tidskriftsartikel (refereegranskat)abstract
- Background exposure to persistent organic pollutants (POPs), lipophilic xenobiotics that accumulate mainly in adipose tissue, has recently emerged as a new risk factor for cardiovascular diseases. This prospective study was performed to evaluate if plasma concentrations of selected POPs predict incident stroke among the elderly. Twenty-one POPs (including 16 polychlorinated biphenyl (PCB) congeners, 3 organochlorine (OC) pesticides, 1 brominated diphenyl ether (BDE), and 1 dioxin) were measured in plasma collected at baseline in 898 participants aged 70 years of the Prospective Investigation of the Vasculature in Uppsala Seniors (PIVUS). Stroke diagnosis was validated by hospital records. During the five year follow-up, 35 subjects developed hospital-treated stroke. After adjusting for known stroke risk factors, most PCBs with 4, 5, or 6 chlorine atoms, p,p'-DDE, trans-nonachlor, and octachlorodibenzo-p-dioxin significantly predicted the risk of stroke. Across quartiles of summary measures of PCBs and OC pesticides, the adjusted ORs were 1.0, 0.8 (95% confidence interval: 0.2-2.5), 1.2 (0.4-3.4), and 2.1 (0.7-6.2) for PCBs and 1.0, 1.2 (0.3-4.2), 2.3 (0.7-6.9), and 3.0 (1.0-9.4) for OC pesticides (P for trend = 0.11 and 0.03, respectively). The adjusted ORs among participants >= 90th percentile of the summary measures were 5.5 (1.7-18.1) for PCBs and 4.0 (1.1-14.6) for OC pesticides; corresponding ORs for those >= 95th percentile were 7.8 (2.1-29.6) and 9.5 (2.3-38.9). Background exposure to POPs may play an important role in development or progression of stroke in the elderly.
|
|
| 54. |
- Lee, Duk-Hee, et al.
(författare)
-
Does Mortality Risk of Cigarette Smoking Depend on Serum Concentrations of Persistent Organic Pollutants? : Prospective Investigation of the Vasculature in Uppsala Seniors (PIVUS) Study
- 2014
-
Ingår i: PLOS ONE. - San Francisco : Public Library Science. - 1932-6203. ; 9:5, s. e95937-
-
Tidskriftsartikel (refereegranskat)abstract
- Cigarette smoking is an important cause of preventable death globally, but associations between smoking and mortality vary substantially across country and calendar time. Although methodological biases have been discussed, it is biologically plausible that persistent organic pollutants (POPs) like polychlorinated biphenyls (PCBs) and organochlorine (OC) pesticides can affect this association. This study was performed to evaluate if associations of cigarette smoking with mortality were modified by serum concentrations of PCBs and OC pesticides. We evaluated cigarette smoking in 111 total deaths among 986 men and women aged 70 years in the Prospective Investigation of the Vasculature in Uppsala Seniors (PIVUS) with mean follow-up for 7.7 years. The association between cigarette smoking and total mortality depended on serum concentration of PCBs and OC pesticides (P value for interaction = 0.02). Among participants in the highest tertile of the serum POPs summary score, former and current smokers had 3.7 (95% CI, 1.5-9.3) and 6.4 (95% CI, 2.3-17.7) times higher mortality hazard, respectively, than never smokers. In contrast, the association between cigarette smoking and total mortality among participants in the lowest tertile of the serum POPs summary score was much weaker and statistically nonsignificant. The strong smoking-mortality association observed among elderly people with high POPs was mainly driven by low risk of mortality among never smokers with high POPs. As smoking is increasing in many low-income and middle-income countries and POPs contamination is a continuing problem in these areas, the interactions between these two important health-related issues should be considered in future research.
|
|
| 55. |
- Lee, Duk-Hee, et al.
(författare)
-
Polychlorinated Biphenyls and Organochlorine Pesticides in Plasma Predict Development of Type 2 Diabetes in the Elderly
- 2011
-
Ingår i: Diabetes Care. - : American Diabetes Association. - 0149-5992 .- 1935-5548. ; 34:8, s. 1778-1784
-
Tidskriftsartikel (refereegranskat)abstract
- OBJECTIVE-Persistent organic pollutants (POPs), lipophilic chemicals that accumulate mainly in adipose tissue, have recently been linked to type 2 diabetes. However, evidence from prospective studies is sparse. This study was performed to evaluate prospective associations of type 2 diabetes with selected POPs among the elderly. RESEARCH DESIGN AND METHODS-Nineteen POPs (14 polychlorinated biphenyl [PCB] congeners, 3 organochlorine pesticides, 1 brominated diphenyl ether, and 1 dioxin) were measured in plasma collected at baseline in 725 participants, aged 70 years, of the Prospective Investigation of the Vasculature in Uppsala Seniors (PIVUS). RESULTS-After adjusting for known type 2 diabetes risk factors, including obesity, odds ratios (ORs) (95% CIs) for type 2 diabetes at age 75 years (n = 36) according to the quintiles of a summary measure of concentrations of PCBs (vs. the lowest quintile) were 4.5, 5.1, 8.8 (1.8-42.7), and 7.5 (1.4-38.8) (P(trend) <0.01). Among organochlorine pesticides, adjusted ORs across concentrations of trans-nonachlor showed that P(trend) = 0.03. Adjusted ORs (95% CIs) across quintiles of the sum of three organochlorine pesticides were 1.1, 1.6, 1.5, and 3.4 (1.0-11.7) (P(trend) = 0.03). Neither brominated diphenyl ether 47 nor dioxin was significantly associated with incident diabetes. The sum of PCBs improved reclassification significantly when added to traditional risk factors for diabetes. CONCLUSIONS-Despite the small number of incident cases, this study found that environmental exposure to some POPs substantially increased risk of future type 2 diabetes in an elderly population.
|
|
| 56. |
- Lee, Duk-Hee, et al.
(författare)
-
Polychlorinated biphenyls and organochlorine pesticides in plasma predict development of type 2 diabetes in the elderly : the prospective investigation of the vasculature in Uppsala Seniors (PIVUS) study
- 2011
-
Ingår i: Diabetes Care. - : American Diabetes Association. - 0149-5992 .- 1935-5548. ; 34:8, s. 1778-1784
-
Tidskriftsartikel (refereegranskat)abstract
- OBJECTIVE: Persistent organic pollutants (POPs), lipophilic chemicals that accumulate mainly in adipose tissue, have recently been linked to type 2 diabetes. However, evidence from prospective studies is sparse. This study was performed to evaluate prospective associations of type 2 diabetes with selected POPs among the elderly.RESEARCH DESIGN AND METHODS: Nineteen POPs (14 polychlorinated biphenyl [PCB] congeners, 3 organochlorine pesticides, 1 brominated diphenyl ether, and 1 dioxin) were measured in plasma collected at baseline in 725 participants, aged 70 years, of the Prospective Investigation of the Vasculature in Uppsala Seniors (PIVUS).RESULTS: After adjusting for known type 2 diabetes risk factors, including obesity, odds ratios (ORs) (95% CIs) for type 2 diabetes at age 75 years (n = 36) according to the quintiles of a summary measure of concentrations of PCBs (vs. the lowest quintile) were 4.5, 5.1, 8.8 (1.8-42.7), and 7.5 (1.4-38.8) (P(trend) <0.01). Among organochlorine pesticides, adjusted ORs across concentrations of trans-nonachlor showed that P(trend) = 0.03. Adjusted ORs (95% CIs) across quintiles of the sum of three organochlorine pesticides were 1.1, 1.6, 1.5, and 3.4 (1.0-11.7) (P(trend) = 0.03). Neither brominated diphenyl ether 47 nor dioxin was significantly associated with incident diabetes. The sum of PCBs improved reclassification significantly when added to traditional risk factors for diabetes.CONCLUSIONS: Despite the small number of incident cases, this study found that environmental exposure to some POPs substantially increased risk of future type 2 diabetes in an elderly population.
|
|
| 57. |
|
|
| 58. |
- Lind, Lars, et al.
(författare)
-
Can Persistent Organic Pollutants And Plastic-Associated Chemicals Cause Cardiovascular Disease?
- 2012
-
Ingår i: Journal of Internal Medicine. - : Wiley. - 0954-6820 .- 1365-2796. ; 271:6, s. 537-553
-
Forskningsöversikt (refereegranskat)abstract
- During the last decade, associations between persistent organic pollutants (POPs), such as polychlorinated biphenyls, dioxins and pesticides, and cardiovascular (CV) risk factors and overt CV disease (CVD) have been reported in humans. Recently, associations between plastic-associated chemicals (PACs), such as bisphenol A and phthalates, and CVD have also begun to emerge. Several approaches to evaluating such associations have been used: accidents with a high level of exposure, occupational exposure studies, geographical studies of subjects living near a contaminated area and traditional case-control or cohort studies with measurements of circulating levels of different environmental contaminants in the general population. Exposure to POPs has consistently been associated with diabetes using all the approaches described above, including prospective studies. The evidence regarding associations between exposure to POPs and other CV risk factors, such as hypertension, obesity and lipids, is less strong, and is mainly based on cross-sectional data. Associations between overt CVD and POPs have been reported using all the above approaches, but prospective data from population-based studies are still lacking to provide firm evidence of an important and independent role of POP exposure in the pathogenesis of CVD. Nevertheless, taken together, current evidence suggests that further longitudinal and experimental studies should be conducted to investigate the effect of exposure to both POPs and PACs, such as bisphenol A and phthalates.
|
|
| 59. |
- Lind, Lars, et al.
(författare)
-
Circulating levels of perfluoroalkyl substances and prevalent diabetes in the elderly
- 2014
-
Ingår i: Diabetologia. - : Springer-Verlag New York. - 0012-186X .- 1432-0428. ; 57:3, s. 473-479
-
Tidskriftsartikel (refereegranskat)abstract
- Several environmental contaminants, such as polychlorinated biphenyls, dioxins, bisphenol A and phthalates, have been linked to diabetes. We therefore investigated whether other kinds of contaminants, perfluoroalkyl substances (PFAS), also called perfluorinated compounds (PFCs), are also associated with diabetes.The Prospective Investigation of the Vasculature in Uppsala Seniors (PIVUS) study investigated 1,016 men and women aged 70 years. Seven PFAS were detected in almost all participant sera by ultra-high performance liquid chromatograph/tandem mass spectrometry. Diabetes was defined as use of hypoglycaemic agents or fasting glucose > 7.0 mmol/l.114 people had diabetes. In the linear analysis, no significant relationships were seen between the seven PFAS and prevalent diabetes. However, inclusion of the quadratic terms of the PFAS revealed a significant non-linear relationship between perfluorononanoic acid (PFNA) and diabetes, even after adjusting for multiple confounders (OR 1.96, 95% CI 1.19, 3.22, p = 0.008 for the linear term and OR 1.25, 95% CI 1.08, 1.44, p = 0.002 for the quadratic term). Perfluorooctanoic acid (PFOA) also showed such a relationship (p = 0.01). PFOA was related to the proinsulin/insulin ratio (a marker of insulin secretion), but none of the PFAS was related to the HOMA-IR (a marker of insulin resistance) following adjustment for multiple confounders.PFNA was related to prevalent diabetes in a non-monotonic fashion in this cross-sectional study, supporting the view that this perfluoroalkyl substance might influence glucose metabolism in humans at the level of exposure seen in the general elderly population.
|
|
| 60. |
- Lind, Lars, et al.
(författare)
-
Circulating levels of secretory- and lipoprotein-associated phospholipase A2 activities : relation to atherosclerotic plaques and future all-cause mortality
- 2012
-
Ingår i: European Heart Journal. - : Oxford University Press (OUP). - 0195-668X .- 1522-9645. ; 33:23, s. 2946-54
-
Tidskriftsartikel (refereegranskat)abstract
- AimsSecretory- and lipoprotein-associated phospholipases A2 (sPLA2 and Lp-PLA2) are enzymes both suggested to be of importance for atherosclerosis. We investigated relationships between the activities of these enzymes in the circulation and atherosclerosis as well as future clinical events.Methods and resultsThe population-based Prospective Investigation of the Vasculature in Uppsala Seniors (PIVUS) study included 1016 randomly selected subjects, all aged 70. The prevalence of carotid artery plaques was recorded by ultrasound (n= 954), and arterial stenosis was assessed by whole-body magnetic resonance angiography (WBMRA, n= 302). Secretory-associated phospholipase A2 [odds ratio 1.23 for 1 SD increase, 95% confidence interval (CI): 1.05-1.44, P= 0.007], but not Lp-PLA2 (P= 0.26), activity was significantly related to carotid atherosclerosis and to the amount of stenosis at WBMRA (P= 0.006) following adjustment for multiple risk factors (waist circumference, serum triglycerides, body mass index, C-reactive protein, high density lipoprotein-C, low density lipoprotein-C, triglycerides, GFR, fasting glucose, blood pressure, statin use, and exercise habits). Secretory-associated phospholipase A2 [hazard ratio (HR) 1.45 for 1 SD increase, 95% CI: 1.15-1.84, P= 0.001], but not Lp-PLA2 (HR 0.95, P= 0.55), activity was a significant risk factor for all-cause mortality (114 had died) during 7.0 years follow-up after adjustment for the risk factors described above. In a sample of 1029 post-myocardial infarction (MI) patients (French registry of Acute ST-elevation and non-ST-elevation Myocardial Infarction), sPLA2 (adjusted HR 1.32 for 1 unit increase, 95% CI: 1.02-1.71, P= 0.036), but not Lp-PLA2 (HR 1.03, P= 0.90), activity predicted death or recurrent MI during 1-year follow-up (n= 136 cases).ConclusionsPLA2 activity was related to atherosclerosis and predicted all-cause mortality in a sample of elderly subjects, as well as death or MI in post-MI patients.
|
|
