Beatriz Valera

Environmental Mercury Exposure and Blood Pressure Among Nunavik Inuit Adults

Epidemiological evidence suggests a negative impact of methylmercury on the cardiovascular system, but findings regarding the effect on blood pressure (BP) are not consistent. We aimed to study the impact of mercury levels on BP among Nunavik Inuit adults. The health survey Qanuippitaa? was conducted in Nunavik (northern Quebec, Canada), and data were obtained from 732 Inuit ≥18 years of age. Anthropometric blood samples, as well as systolic BP and diastolic BP, were assessed. Pulse pressure (systolic BP−diastolic BP) was calculated. Mercury blood concentration was used as a biomarker of recent exposure. Simple relations between mercury and BP parameters were studied by using the Pearson correlation, whereas multiple regressions were performed to control for confounders. Mean age of the participants was 34.3 years (95% CI: 33.6 to 34.9 years). Systolic BP, diastolic BP, and pulse pressure means were 117 mm Hg (95% CI: 116 to 118 mm Hg), 73 mm Hg (95% CI: 72 to 74 mm Hg), and 43 mm Hg (95% CI: 42 to 44 mm Hg), respectively. Mercury mean was 50.2 nmol/L. In multivariable analyses, mercury was associated with systolic BP (&bgr;=2.14; P =0.0004), whereas the association with diastolic BP was near the significance level (&bgr;=0.96; P =0.069). In conclusion, mercury is associated with increasing BP and pulse pressure among Nunavik Inuit adults after considering the effect of fish nutrients (n-3 fatty acids and selenium) and other confounders.

Cardiac autonomic activity and blood pressure among Nunavik Inuit adults exposed to environmental mercury: a cross-sectional study

BackgroundMercury is a contaminant that reaches high levels in Nunavik (North of Quebec). It is transformed into methylmercury (MeHg) and accumulated in marine mammals and predator fish, an important part of the traditional Inuit diet. MeHg has been suggested to affect BP in adults and children while the influence on HRV has only been studied in children. We aimed to assess the impact of MeHg levels on HRV and BP in Inuit adults from Nunavik.MethodsIn the fall of 2004, the «Qanuippitaa?» Health Survey was conducted in Nunavik (Quebec, Canada) and information on HRV was collected among 280 adults aged 40 years and older. Indicators of the time and frequency domains of HRV were derived from a 2-hour Holter recording. BP was measured according to the Canadian Coalition for High Blood Pressure technique. Pulse pressure (PP) was the difference between systolic (SBP) and diastolic blood pressure (DBP). Blood mercury concentration was used as exposure biomarker. Statistical analysis was conducted through linear regression and multivariable linear regression was used to control for confounders.ResultsMercury was negatively correlated with low frequency (LF) (r = -0.18; p = 0.02), the standard deviation of RR intervals (SDNN) (r = -0.14; p = 0.047) and the coefficient of variation of RR intervals (CVRR) (r = -0.18; p = 0.011) while correlations with other HRV parameters did not reach statistical significance. After adjusting for confounders, the association with LF (beta = -0.006; p = 0.93) became non significant. However, the association with SDANN became statistically significant (beta = -0.086; p = 0.026) and CVRR tended to decrease with blood mercury concentrations (beta = -0.057; p = 0.056). Mercury was positively correlated with SBP (r = 0.25; p < 0.0001) and PP (r = 0.33; p < 0.0001). After adjusting for confounders, these associations remained statistically significant (beta SBP = 4.77; p = 0.01 and beta PP = 3.40; p = 0.0036). Moreover, most of the HRV parameters correlated well with BP although SBP the best before adjustment for mercury exposure.ConclusionThe results of this study suggest a deleterious impact of mercury on BP and HRV in adults. SBP and PP increased with blood mercury concentrations while SDANN decreased with blood mercury concentrations.

Influence of mercury exposure on blood pressure, resting heart rate and heart rate variability in French Polynesians: a cross-sectional study

BackgroundPopulations which diet is rich in seafood are highly exposed to contaminants such as mercury, which could affect cardiovascular risk factorsObjectiveTo assess the associations between mercury and blood pressure (BP), resting heart rate (HR) and HR variability (HRV) among French PolynesiansMethodsData were collected among 180 adults (≥ 18 years) and 101 teenagers (12-17 years). HRV was measured using a two-hour ambulatory electrocardiogram (Holter) and BP was measured using a standardized protocol. The association between mercury and HRV and BP parameters was studied using analysis of variance (ANOVA) and analysis of covariance (ANCOVA)ResultsAmong teenagers, the high frequency (HF) decreased between the 2nd and 3rd tertile (380 vs. 204 ms2, p = 0.03) and a similar pattern was observed for the square root of the mean squared differences of successive R-R intervals (rMSSD) (43 vs. 30 ms, p = 0.005) after adjusting for confounders. In addition, the ratio low/high frequency (LF/HF) increased between the 2nd and 3rd tertile (2.3 vs. 3.0, p = 0.04). Among adults, the standard deviation of R-R intervals (SDNN) tended to decrease between the 1st and 2nd tertile (84 vs. 75 ms, p = 0.069) after adjusting for confounders. Furthermore, diastolic BP tended to increase between the 2nd and 3rd tertile (86 vs. 91 mm Hg, p = 0.09). No significant difference was observed in resting HR or pulse pressure (PP)ConclusionsMercury was associated with decreased HRV among French Polynesian teenagers while no significant association was observed with resting HR, BP, or PP among teenagers or adults

Hypertension among the Inuit from Nunavik: should we expect an increase because of obesity?

Objectives. Because of their recent adoption of a Westernized lifestyle, an increased risk of developing hypertension (HTN) is suspected among Inuit populations. This study aimed to assess the exact prevalence of HTN in Nunavik Inuit and to examine its association with other major risk factors of cardiovascular disease. Study design. A cross-sectional population-based study. Methods. We analysed biological and anthropometric data and the medical history of 832 Inuit. Results. The overall prevalence of HTN (≥140/90 mmHg or the use of medication) was 19% with no gender difference. Obesity (body mass index [BMI] ≥30 kg/m2) was the highest prevalent cardiovascular risk factor (23%), and was significantly associated with HTN (OR for BMI&25 kg/m2 vs. BMI 30–34 kg/m2: 7.9 [3.5–17.9]; OR for BMI&25 kg/m2 vs. BMI ≥35 kg/m2: 14.4 [5.6–36.7]). An increase in odds of prehypertension (preHTN) (130–139/80–89 mmHg) was also observed as the BMI increased (p for trend, p&0.0001). Conclusion. The prevalence of HTN in the Inuit populations has reached values similar to those of their Westernized counterparts. Furthermore, not only HTN but also preHTN states are significantly associated with obesity even after adjusting for confounding variables. These results clearly indicate that HTN is becoming a growing health challenge in Nunavik because of pandemic obesity.

Influence of n-3 fatty acids on cardiac autonomic activity among Nunavik Inuit adults

Objectives. Inuit from Nunavik (northern Quebec) consume large amounts of fish and marine mammals, which are important sources of n-3 polyunsaturated fatty acids (n-3 PUFAs). These substances have a beneficial impact on heart rate (HR) and heart rate variability (HRV). However, it is unknown if this beneficial impact remains significant in populations with high mercury exposure. The study assessed the impact of n-3 PUFAs (Docosahexaenoic [DHA] and Eicosapentaenoic acid [EPA]) on resting HR and HRV among Nunavik Inuit adults considering mercury and other potential confounders. Study design. Cross-sectional study employing clinical measurements. Methods. Complete data were collected among 181 adults ≥40 years old (109 women and 72 men) living in the 14 coastal villages of Nunavik. Several indices of HRV were derived from a 2-hour Holter monitoring assessment. n-3 PUFAs levels were measured in membrane erythrocytes. Simple linear regression was used to analyse the relationship between n-3 PUFAs levels and resting HR and HRV parameters while multiple linear regressions were carried out to control for confounders. Results. In the overall analyses, EPA was associated with SDANN (β=0.07, p=0.04) and LF norm (β=- 1.84, p=0.03) after adjusting for confounders. Among women, DHA was associated with resting HR (β=-1.40, p=0.03) while EPA was associated with SDNN (β=0.08, p=0.03), SDANN (β=0.09, p=0.02) and resting HR (β=-2.61, p=0.002). No significant association was observed in men. Conclusions. These results suggest a beneficial impact of n-3 PUFAs on resting HR and HRV among Nunavik Inuit women.

Methylmercury exposure, PON1 gene variants and serum paraoxonase activity in Eastern James Bay Cree adults

There is growing evidence that cardiovascular health can be affected by exposure to methylmercury (MeHg), by a mechanism involving oxidative stress. Paraoxonase 1 (PON1) is a high-density lipoprotein-bound enzyme that hydrolyzes toxic oxidized lipids and protects against cardiovascular diseases. Evidence from in vitro studies indicates that MeHg can inhibit PON1 activity but little is known regarding this effect in humans. We investigated whether increased blood mercury levels are associated with decreased serum PON1 activity in Cree people who are exposed to MeHg by fish consumption. We conducted a multi-community study of 881 Cree adults living in Eastern James Bay communities (Canada). Multivariate analyses considered sociodemographic, anthropometric, clinical, dietary and lifestyle variables and six PON1 gene variants (rs705379 (−108C/T), rs662 (Q192R), rs854560 (L55M), rs854572 (−909C/G), rs854571 (−832C/T) and rs705381 (−162C/T)). In a multiple regression model adjusted for all potential confounding factors and the rs854560 PON1 variant, a statistically significant MeHg*rs705379 interaction was observed. Blood mercury levels were inversely associated with serum PON1 activities in individual homozygous for the −108T allele (P=0.009). Our results suggest a gene–environment interaction between the rs705379 polymorphism and MeHg exposure on PON1 activity levels in this aboriginal population. This finding will need to be replicated in other population studies.

The ethnoepidemiology of obesity.

The prevalence of overweight and obesity varies significantly across ethnic groups and among aboriginal people in Canada and appears to be increasing overall in children and youth, which will have significant health consequences in the future. Individual health behaviours, genetic predisposition, and community-level factors all contribute to the high burden of overweight and obesity across communities in Canada. Preliminary studies indicate that individuals who live in neighbourhoods in Canada with increased walkability, fewer fast food outlets, and higher socioeconomic status have lower rates of overweight/obesity when compared with other neighbourhoods. However, more research is required to understand the impact of community level factors on overweight/obesity trends in Canadian ethnic groups, including children and youth, and aboriginal people.

Influence of polyunsaturated fatty acids on blood pressure, resting heart rate and heart rate variability among French Polynesians.

Objective: To analyze the associations between marine n-3 polyunsaturated fatty acids (PUFAs) and blood pressure (BP), resting heart rate (HR), and heart rate variability (HRV) in a population highly exposed to methylmercury through the diet. Methods: Concentrations of docosahexaenoic acid (DHA) and eicosapentaenoic acid (EPA) in erythrocytes membranes were measured in 180 French Polynesian adults (≥18 years) residing in Tubuai, which is a community with a traditional lifestyle, or Papeete, which has a modern lifestyle. HRV was measured using a 2-hour ambulatory electrocardiogram (Holter). Resting HR and BP were measured using standardized protocols and pulse pressure (PP) was calculated as systolic BP − diastolic BP. The associations between n-3 PUFAs and the dependent variables were studied using simple and multiple linear regressions. Results: Increasing DHA concentration was associated with lower resting HR (β = −2.57, p = 0.005) and diastolic BP (β = −1.96, p = 0.05) and higher HRV in multivariable models. Specifically, DHA was associated with high frequency (HF; β = 0.19, p = 0.02) and the square root of the mean squared differences of successive R-R intervals (difference between two consecutive R waves; rMSSD; β = 0.08, p = 0.03), which are specific indices of the parasympathetic activity of the autonomic nervous system. Conclusion: DHA was associated with lower BP and resting HR and higher HRV among French Polynesians who are also exposed to high methylmercury levels.

Daily Steps Threshold to Improve Cardiovascular Disease Risk Factors During the Year After an Acute Coronary Syndrome

PURPOSE: To evaluate the daily steps threshold associated with improved cardiovascular disease risk factors during the first year following an acute coronary syndrome. METHODS: Subjects (N = 41) were recruited during hospitalization for an acute coronary syndrome. A blinded pedometer with a 7-day memory (NL-2000) was used at baseline, 3, 6, 9, and 12 months following hospitalization. Cardiovascular disease risk factors were measured at baseline, 6, and 12 months after discharge. Subjects who maintained a mean of 7500 steps per day or more at each time period were classified into the active group, whereas those who did not maintain this threshold were classified into the less active group. RESULTS: The active group included 25 subjects, whereas 16 subjects were included in the less active group. Daily steps mean ± SEM was different between groups at 6 and 12 months followup (11 320 ± 3380 vs 5503 ± 1502 and 10 507 ± 2861 vs 6624 ± 3295 steps per day, respectively; both P < .001). Based on the analysis of variance for repeated measures (ANOVA-RM), the active group showed lower triglycerides (P < .01), lower waist circumference (P < .01), and higher high-density lipoprotein–cholesterol (HDL-C) (P = .04) at 12 months. Interaction effects (group × followup) were also significant for HDL-C (P = .01) and triglycerides (P = .01) after adjustment for age, gender, and baseline waist circumference. CONCLUSION: Targeting

Associations between plasma persistent organic pollutant levels and blood pressure in Inuit adults from Nunavik

7500 daily steps during 1 year may be efficient to maintain lowest waist circumference and to improve lipid profile during the year following an acute coronary syndrome. It could be considered a starting target point to initiate changes in physical activity behavior.