Eric Dewailly

Indigenous health in the Arctic: an overview of the circumpolar Inuit population.

The health of the Inuit has undergone substantial changes over the past five centuries, as a result of social, cultural, and economic changes brought about by interactions with Europeans. This process was accelerated considerably in the second half of the twentieth century. The incidence of infectious diseases has declined considerably but is still high compared with Western societies. Chronic diseases such as diabetes and cardiovascular disease are on the increase, while accidents, suicides, violence, and substance abuse are of major importance for the pattern of ill health in most Inuit communities. Lifestyle changes, social change, and changes in society and the environment are major determinants of health among the Inuit.

Impact of Waist Circumference on the Relationship Between Blood Pressure and Insulin: The Quebec Health Survey

Hyperinsulinemia has been suggested to be involved in the etiology of obesity-associated hypertension. The objective of the present study was to quantify, in a population-based study, the respective contributions of excess adiposity (body mass index [BMI]), waist circumference (WC), fasting insulin levels, and insulin sensitivity to the variation of resting blood pressure. The Quebec Health Survey was used to obtain fasting plasma insulin and glucose levels and resting blood pressure as well as anthropometric measurements in a representative sample of 907 men and 937 women. When the sample was divided into tertiles of BMI and further stratified on the basis of the 50th percentile of WC (88 cm in men), nonobese men in the first BMI tertile (<23.2 kg/m2) but with abdominal obesity were characterized by an increased systolic blood pressure (SBP) compared with nonobese men with low WC (130±18 versus 120±11 mm Hg; mean±SD; P=0.075). The SBP was comparable to SBP values measured among men in the top BMI tertile (129±14 mm Hg for BMI ≥26.6 kg/m2). When subjects were classified into tertiles of fasting insulin and WC, no association between insulin levels and blood pressure was noted, once the variation in WC was considered. Insulin sensitivity (estimated with homeostasis model assessment [HOMA]) did not explain variation in blood pressure in men, whereas the contribution of HOMA in women was of marginal clinical significance (R2 of <1.3%; P<0.0001). These results suggest that the documented association between obesity, fasting insulin, insulin sensitivity, and blood pressure is largely explained by concomitant variation in WC.

Environmental contaminants and human health in the Canadian Arctic.

The third Canadian Arctic Human Health Assessment conducted under the Canadian Northern Contaminants Program (NCP), in association with the circumpolar Arctic Monitoring and Assessment Programme (AMAP), addresses concerns about possible adverse health effects in individuals exposed to environmental contaminants through a diet containing country foods. The objectives here are to: 1) provide data on changes in human contaminant concentrations and exposure among Canadian Arctic peoples; 2) identify new contaminants of concern; 3) discuss possible health effects; 4) outline risk communication about contaminants in country food; and 5) identify knowledge gaps for future contaminant research and monitoring. The nutritional and cultural benefits of country foods are substantial; however, some dietary studies suggest declines in the amount of country foods being consumed. Significant declines were found for most contaminants in maternal blood over the last 10 years within all three Arctic regions studied. Inuit continue to have the highest levels of almost all persistent organic pollutants (POPs) and metals among the ethnic groups studied. A greater proportion of people in the East exceed Health Canadas guidelines for PCBs and mercury, although the proportion of mothers exceeding these guidelines has decreased since the previous assessment. Further monitoring and research are required to assess trends and health effects of emerging contaminants. Infant development studies have shown possible subtle effects of prenatal exposure to heavy metals and some POPs on immune system function and neurodevelopment. New data suggest important beneficial effects on brain development for Inuit infants from some country food nutrients. The most successful risk communication processes balance the risks and benefits of a diet of country food through input from a variety of regional experts and the community, to incorporate the many socio-cultural and economic factors to arrive at a risk management decision that will be the most beneficial in Arctic communities.

Beneficial Effects of a Polyunsaturated Fatty Acid on Infant Development: Evidence from the Inuit of Arctic Quebec

OBJECTIVES To examine the relation of cord plasma docosahexaenoic acid (DHA) concentration to gestation length, birth size, growth, and infant visual acuity, cognitive, and motor development and the effects on growth and development associated with DHA intake from breast-feeding. STUDY DESIGN DHA, other polyunsaturated fatty acids, and 3 environmental contaminants (polychlorinated biphenyls, mercury, and lead) were assessed in cord plasma and maternal plasma and milk in 109 Inuit infants in Arctic Quebec. Multiple regression was used to examine the relation of cord DHA and DHA from breast-feeding on growth and development at 6 and 11 months, after controlling for contaminant exposure and other potential confounders. RESULTS Higher cord DHA concentration was associated with longer gestation, better visual acuity and novelty preference on the Fagan Test at 6 months, and better Bayley Scale mental and psychomotor performance at 11 months. By contrast, DHA from breast-feeding was not related to any indicator of cognitive or motor development in this full-term sample. CONCLUSIONS The association of higher cord DHA concentration with more optimal visual, cognitive, and motor development is consistent with the need for substantial increases in this critically important fatty acid during the third trimester spurt of synaptogenesis in brain and photoreceptor development.

Thyroid Function and Plasma Concentrations of Polyhalogenated Compounds in Inuit Adults

Background Several ubiquitous polyhalogenated compounds (PHCs) have been shown to alter thyroid function in animal and in vitro studies. So far, epidemiologic studies have focused on the potential effect of a small number of them, namely, polychlorinated biphenyls (PCBs) and some organochlorines (OCs), without paying attention to other important PHCs. Objectives We investigated the relationship between exposure to several PHCs and thyroid hormone homeostasis in Inuit adults from Nunavik. Methods We measured thyroid parameters [thyroid-stimulating-hormone (TSH), free thyroxine (fT4), total triiodothyronine (tT3), and thyroxine-binding globulin (TBG)] and concentrations of 41 contaminants, including PCBs and their metabolites, organochlorine pesticides (OCPs), polybrominated diphenyl ethers (PBDEs), perfluorooctanesulfonate (PFOS), and a measure of dioxin-like compounds, detected in plasma samples from Inuit adults (n = 623). Results We found negative associations between tT3 concentrations and levels of 14 PCBs, 7 hydroxylated PCBs (HO-PCBs), all methylsulfonyl metabolites of PCBs (MeSO2-PCBs), and 2 OCPs. Moreover, we found negative associations between fT4 levels and hexachlorobenzene Concentrations. TBG concentrations were inversely related to 8 PCBs, 5 HO-PCBs, and 3 OCPs. Exposure to BDE-47 was positively related to tT 3, whereas PFOS concentrations were negatively associated with TSH, tT3, and TBG and positively with fT4 concentrations. Conclusion Exposure to several PHCs was associated with modifications of the thyroid parameters in adult Inuit, mainly by reducing tT3 and TBG circulating concentrations. The effects of PFOS and BDE-47 on thyroid homeostasis require further investigation because other human populations display similar or higher concentrations of these chemicals.

Lead, Mercury, and Organochlorine Compound Levels in Cord Blood in Québec, Canada

We conducted this study to evaluate blood levels of lead, mercury, and organochlorine compounds in newborns in the Province of Quebec. During 1993 to 1995, we carried out a survey in 10 hospitals located in southern Quebec. During that time, umbilical cord blood samples were obtained from 1109 newborns, and we analyzed each for lead, mercury, 14 polychlorinated biphenyl congeners, and 11 chlorinated pesticides. We used the geometric mean and 95% confidence interval (CI) to describe the results. Mean concentrations of lead and mercury in cord blood were 0.076 micromol/l (95% CI = 0.074, 0.079) and 4.82 nmol/l (95% CI = 4.56, 5.08), respectively. The mean concentrations of total polychlorinated biphenyls (Aroclor 1260) and dichlorodiphenyl dichloroethylene were 0.514 microg/I (95% CI = .493, 0.536) and 0.412 microg/l (95% CI = 0.390, 0.435), respectively. We observed a statistically significant relationship between maternal age and cord blood concentrations of (a) lead, (b) mercury, (c) polychlorinated biphenyls, and (d) dichlorodiphenyl dichloroethylene. In addition, maternal smoking during pregnancy was associated with cord blood lead levels. The cord blood concentrations of lead, mercury, polychlorinated biphenyls, and dichlorodiphenyl dichloroethylene we measured in our study were the lowest levels recently reported in industrialized countries. The results of this study underline the role of public health authorities in the evaluation of biological levels of environmental contaminants among children for the assessment of risk of adverse health effects.

Organochlorine exposure and the risk of endometriosis

OBJECTIVE To compare mean concentrations of organochlorine in women with a new diagnosis of endometriosis and in controls. DESIGN Case-control study. SETTING Women attending an institutional clinic of reproductive endocrinology. PATIENT(S) Cases and controls were selected among women who underwent laparoscopy for chronic pelvic pain, infertility, or tubal fulguration between January 1994 and December 1994. Eighty-six women with endometriosis and 70 controls, matched for the indication for laparoscopy, were recruited. MAIN OUTCOME MEASURE(S) Mean organochlorine plasma concentrations of 14 polychlorinated biphenyl congeners and 11 chlorinated pesticides were compared between the cases and controls. Analysis of covariance was used to adjust means for confounding variables, and odds ratios were estimated by logistic regression. RESULT(S) Crude geometric mean concentrations did not differ significantly between cases and controls for any of the organochlorine compounds. Similarly, crude or adjusted means of the sum of polychlorinated biphenyl congeners, the sum of chlordanes, or the sum of dichlorodiphenyltrichloroethanes did not differ between the groups. There was no significant linear trend in the adjusted odds ratios for endometriosis as organochlorine concentrations increased. CONCLUSION(S) These results suggest that exposure to polychlorinated biphenyls and chlorinated pesticides during adulthood is not associated with endometriosis in the general population.

Omega-3 fatty acids and risk of cognitive impairment and dementia.

It has been suggested that the dietary intake of omega-3 polyunsaturated fatty acids could be inversely related to the risk of dementia and cognitive decline. This analysis examined the association between plasma concentration of omega-3 polyunsaturated fatty acids and prevalence and incidence of cognitive impairment and dementia. Data are reported on subjects 65 years or older who had a complete clinical evaluation at the first two waves (1991-1992 and 1996-1997) of the Canadian Study of Health and Aging. Main outcome measures were cognitive impairment and dementia by mean relative plasma concentrations of fatty acids in the phospholipid fraction at baseline. Results were adjusted for age, sex, education, smoking, alcohol intake, body mass index, history of cardiovascular disease, and apolipoprotein E e4 genotype. In the cross-sectional analysis, no significant difference in omega-3 polyunsaturated fatty acid concentrations was observed between controls and both prevalent cases of cognitive impairment and dementia. In the prospective analysis, a higher eicosapentaenoic acid (p < 0.01) concentration was found in cognitively impaired cases compared to controls while higher docosahexaenoic acid (p < 0.07), omega-3 (p < 0.04) and total polyunsaturated fatty acid (p < 0.03) concentrations were found in dementia cases. These findings do not support the hypothesis that omega-3 polyunsaturated fatty acids play a protective role in cognitive function and dementia.

Effect of prenatal exposure to polychlorinated biphenyls on incidence of acute respiratory infections in preschool Inuit children.

Objective We set out to assess whether environmental prenatal exposure to polychlorinated biphenyls (PCBs) is associated with incidence of acute respiratory infections in preschool Inuit children. Study design We reviewed the medical charts of 343 children from 0 to 5 years of age and evaluated the associations between PCB-153 concentration in umbilical cord plasma and the incidence rates of acute otitis media (AOM) and of upper and lower respiratory tract infections (URTIs and LRTIs, respectively). Results The incidence rates of AOM and LRTIs were positively associated with prenatal exposure to PCBs. Compared with children in the first quartile of exposure (least exposed), children in fourth quartile (most exposed) had rate ratios of 1.25 (p < 0.001) and 1.40 (p < 0.001) for AOM and LRTIs, respectively. There was no association between prenatal PCB exposure and incidence rate of URTIs or hospitalization. Conclusion Prenatal exposure to PCBs could be responsible for a significant portion of respiratory infections in children of this population.

Acute infections and environmental exposure to organochlorines in Inuit infants from Nunavik

The Inuit population of Nunavik (Canada) is exposed to immunotoxic organochlorines (OCs) mainly through the consumption of fish and marine mammal fat. We investigated the effect of perinatal exposure to polychlorinated biphenyls (PCBs) and dichlorodiphenyldichloroethylene (DDE) on the incidence of acute infections in Inuit infants. We reviewed the medical charts of a cohort of 199 Inuit infants during the first 12 months of life and evaluated the incidence rates of upper and lower respiratory tract infections (URTI and LRTIs, respectively), otitis media, and gastrointestinal (GI) infections. Maternal plasma during delivery and infant plasma at 7 months of age were sampled and assayed for PCBs and DDE. Compared to rates for infants in the first quartile of exposure to PCBs (least exposed), adjusted rate ratios for infants in higher quartiles ranged between 1.09 and 1.32 for URTIs, 0.99 and 1.39 for otitis, 1.52 and 1.89 for GI infections, and 1.16 and 1.68 for LRTIs during the first 6 months of follow-up. For all infections combined, the rate ratios ranged from 1.17 to 1.27. The effect size was similar for DDE exposure but was lower for the full 12-month follow-up. Globally, most rate ratios were > 1.0, but few were statistically significant (p < 0.05). No association was found when postnatal exposure was considered. These results show a possible association between prenatal exposure to OCs and acute infections early in life in this Inuit population.