Postnatal methylmercury exposure and neurodevelopmental outcomes at 7 years of age in the Seychelles Child Development Study Nutrition Cohort 2

BACKGROUND

Consumption of fish yields many nutritional benefits, but also results in exposure to methylmercury (MeHg). The developing brain is known to be particularly susceptible to MeHg toxicity in high doses. However, the potential impact of low-level environmental exposure from fish consumption on children's neurodevelopment remains unclear.

METHODS

We investigated postnatal MeHg exposure at 7 years and its association with a battery of 17 neurodevelopmental outcomes in a subset of children (n = 376) from 1535 enrolled mother-child pairs in Nutrition Cohort 2 of the Seychelles Child Development Study (SCDS NC2). Each outcome was modeled in relation to postnatal MeHg exposure using linear regression, adjusting for prenatal MeHg exposure, levels of maternal polyunsaturated fatty acids (PUFA), and several other covariates known to be associated with neurodevelopmental outcomes.

RESULTS

Median postnatal MeHg exposure at 7 years was 2.5 ppm, while the median prenatal MeHg exposure was 3.5 ppm. We found no statistically significant associations between postnatal MeHg exposure and any of the 17 neurodevelopmental outcomes after adjusting for prenatal MeHg exposure and other covariates.

CONCLUSIONS

These findings are consistent with previous cross-sectional analyses of the SCDS Main Cohort. Continued follow-up of the entire NC2 cohort at later ages with repeated exposure measures is needed to further confirm these findings.

Associations between time-weighted postnatal methylmercury exposure from fish consumption and neurodevelopmental outcomes through 24 years of age in the Seychelles Child Development Study Main Cohort

PURPOSE

Methylmercury (MeHg) is a known neurodevelopmental toxicant in sufficient dosage and is universally found in fish. Current fish advisories for children are based on epidemiology studies examining prenatal exposure with a premise that MeHg exposure resulting from children eating fish could also be neurotoxic and have long-term consequences. However, the evidence that this assumption is true is limited. We investigated postnatal MeHg exposure from regular fish consumption using time weighted Hg measurements to determine if there are neurotoxic consequences.

METHODS

We examined 85 neurodevelopmental outcomes measured from ages 9-24 years in the Seychelles Child Development Study Main Cohort (n = 312-550) and examined their association with time-weighted measures of postnatal MeHg exposure in childhood and early adulthood. Postnatal MeHg exposure measured in the first cm of participants' hair samples collected at seven evaluations were used to create two time-weighted (TW) average MeHg exposure metrics, one for childhood (TW-C) and the other for early adulthood (TW-A). TW-C was based on Hg measures at three ages between 6 months and 5.5 years, and TW-A was based on Hg measured at up to four ages between 17 and 24 years. We examined the association between each of these exposure metrics and the neurodevelopmental outcomes using linear regression with adjustment for covariates known to influence neurodevelopmental outcomes.

RESULTS

There were 14 statistically significant associations between a postnatal metric and an endpoint. Six were associated with the TW-C and eight with the TW-A. Thirteen were adverse. Only the TW-C association at 9 years with the Bender Gestalt error score showed improvement. TW-C was adversely associated at 9 years with the Continuous Performance Task risk score, at 22 years with the Boston Naming Test (BNT) total and no cues scores, and at 24 years with the Test of Variables of Attention (TOVA) auditory response time variability and visual response time mean on the logarithmic scale. TW-A was adversely associated at 17 years with the Wisconsin Card Sorting Test % total errors, the Woodcock-Johnson passage comprehension, and the CANTAB rapid visual information processing false alarms, and at 22 years with the BNT total and no cue scores, the CANTAB rapid visual information processing false alarms and the intra-extra dimensional shift total errors and trials.

CONCLUSION

These findings suggest that postnatal MeHg exposure may be adversely associated with neurodevelopmental outcomes in early adulthood. However, the associations are statistical and of unknown, if any, clinical significance. The results need confirmation in other cohorts.

Consumption of Monounsaturated Fatty Acids Is Associated with Improved Cardiometabolic Outcomes in Four African-Origin Populations Spanning the Epidemiologic Transition

Long-chain omega-3 PUFAs, specifically eicosapentaenoic acid (EPA) and docosahexaenoic acid (DHA), are of increasing interest because of their favorable effect on cardiometabolic risk. This study explores the association between omega 6 and 3 fatty acids intake and cardiometabolic risk in four African-origin populations spanning the epidemiological transition. Data are obtained from a cohort of 2500 adults aged 25-45 enrolled in the Modeling the Epidemiologic Transition Study (METS), from the US, Ghana, Jamaica, and the Seychelles. Dietary intake was measured using two 24 h recalls from the Nutrient Data System for Research (NDSR). The prevalence of cardiometabolic risk was analyzed by comparing the lowest and highest quartile of omega-3 (EPA+ DHA) consumption and by comparing participants who consumed a ratio of arachidonic acid (AA)/EPA + DHA ≤4:1 and >4:1. Data were analyzed using multiple variable logistic regression adjusted for age, gender, activity, calorie intake, alcohol intake, and smoking status. The lowest quartile of EPA + DHA intake is associated with cardiometabolic risk 2.16 (1.45, 3.2), inflammation 1.59 (1.17, 2.16), and obesity 2.06 (1.50, 2.82). Additionally, consuming an AA/EPA + DHA ratio of >4:1 is also associated with cardiometabolic risk 1.80 (1.24, 2.60), inflammation 1.47 (1.06, 2.03), and obesity 1.72 (1.25, 2.39). Our findings corroborate previous research supporting a beneficial role for monounsaturated fatty acids in reducing cardiometabolic risk.

Prevalence and Correlates of Behavioral Non-Communicable Diseases Risk Factors among Adolescents in the Seychelles: Results of a National School Survey in 2015

The aim of this study was to investigate the prevalence and correlates of behavioral non-communicable disease (NCD) risk factors among a national sample of school-going adolescents in the Seychelles. Cross-sectional data were analyzed from 2540 school adolescents (median age 14 years, interquartile range = 2), in the Seychelles "Global School-Based Student Health Survey (GSHS)" in 2015. Behavioral NCD risk factors (current tobacco use, current alcohol use, inadequate fruit and vegetable consumption, soft drink consumption, overweight or obesity, physical inactivity, and leisure-time sedentary behavior) were assessed by self-report. Among the seven individual behavioral risk factors, the highest prevalence was physical inactivity (82.7%), followed by daily soft drink consumption (68.3%), inadequate fruit and vegetable consumption (60.9%), leisure-time sedentary behavior (51.0%), current alcohol use (47.6%), overweight or obesity (28.2%), and current tobacco use (23.4%). The total mean number of behavioral NCD risk factors was 3.6 (Standard Deviation = 1.3), and the proportion of co-occurrence of having three or more behavioral NCD risk factors was 80.7%. In adjusted linear regression analysis, male sex, older age, and psychological distress were positively, and school attendance and peer support were negatively associated with the total number of behavioral NCD risk factors. A high prevalence of multiple behavioral NCD risk factors were found and several associated factors were identified, such as male sex, older age, psychological distress, school truancy, and lack of peer support, which may help in aiding intervention programs in this population.

The Association of Dietary Fiber Intake with Cardiometabolic Risk in Four Countries across the Epidemiologic Transition

The greatest burden of cardiovascular disease is now carried by developing countries with cardiometabolic conditions such as metabolic syndrome, obesity and inflammation believed to be the driving force behind this epidemic. Dietary fiber is known to have protective effects against obesity, type 2 diabetes, cardiovascular disease and the metabolic syndrome. Considering the emerging prevalence of these cardiometabolic disease states across the epidemiologic transition, the objective of this study is to explore these associations of dietary fiber with cardiometabolic risk factors in four countries across the epidemiologic transition. We examined population-based samples of men and women, aged 25⁻45 of African origin from Ghana, Jamaica, the Seychelles and the USA. Ghanaians had the lowest prevalence of obesity (10%), while Jamaicans had the lowest prevalence of metabolic syndrome (5%) across all the sites. Participants from the US presented with the highest prevalence of obesity (52%), and metabolic syndrome (22%). Overall, the Ghanaians consumed the highest dietary fiber (24.9 ± 9.7 g), followed by Jamaica (16.0 ± 8.3 g), the Seychelles (13.6 ± 7.2 g) and the lowest in the USA (14.2 ± 7.1 g). Consequently, 43% of Ghanaians met the fiber dietary guidelines (14 g/1000 kcal/day), 9% of Jamaicans, 6% of Seychellois, and only 3% of US adults. Across all sites, cardiometabolic risk (metabolic syndrome, inflammation and obesity) was inversely associated with dietary fiber intake, such that the prevalence of metabolic syndrome was 13% for those in the lowest quartile of fiber intake, compared to 9% those in the highest quartile of fiber intake. Notably, twice as many of participants (38%) in the lowest quartile were obese compared to those in the highest quartile of fiber intake (18%). These findings further support the need to incorporate strategies and policies to promote increased dietary fiber intake as one component for the prevention of cardiometabolic risk in all countries spanning the epidemiologic transition.

Human leptospirosis in Seychelles: A prospective study confirms the heavy burden of the disease but suggests that rats are not the main reservoir

Background

Leptospirosis is a bacterial zoonosis caused by pathogenic Leptospira for which rats are considered as the main reservoir. Disease incidence is higher in tropical countries, especially in insular ecosystems. Our objectives were to determine the current burden of leptospirosis in Seychelles, a country ranking first worldwide according to historical data, to establish epidemiological links between animal reservoirs and human disease, and to identify drivers of transmission.

Methods

A total of 223 patients with acute febrile symptoms of unknown origin were enrolled in a 12-months prospective study and tested for leptospirosis through real-time PCR, IgM ELISA and MAT. In addition, 739 rats trapped throughout the main island were investigated for Leptospira renal carriage. All molecularly confirmed positive samples were further genotyped.

Results

A total of 51 patients fulfilled the biological criteria of acute leptospirosis, corresponding to an annual incidence of 54.6 (95% CI 40.7–71.8) per 100,000 inhabitants. Leptospira carriage in Rattus spp. was overall low (7.7%) but dramatically higher in Rattus norvegicus (52.9%) than in Rattus rattus (4.4%). Leptospira interrogans was the only detected species in both humans and rats, and was represented by three distinct Sequence Types (STs). Two were novel STs identified in two thirds of acute human cases while noteworthily absent from rats.

Conclusions

This study shows that human leptospirosis still represents a heavy disease burden in Seychelles. Genotype data suggests that rats are actually not the main reservoir for human disease. We highlight a rather limited efficacy of preventive measures so far implemented in Seychelles. This could result from ineffective control measures of excreting animal populations, possibly due to a misidentification of the main contaminating reservoir(s). Altogether, presented data stimulate the exploration of alternative reservoir animal hosts.

Leptospirosis is an emerging environmental infectious disease caused by corkscrew shaped bacteria called Leptospira. Humans usually get infected during recreational or work-related outdoor activities through contact with urine excreted by animal reservoirs. As a zoonotic disease, leptospirosis is a good example of the One Health concept for it links humans, animals and ecosystems in a web of pathogen maintenance and transmission. This zoonosis is highly prevalent in the tropics and especially in tropical islands. Seychelles archipelago has been reported as the country with highest human incidence worldwide, although figures are based on dated studies and/or poorly specific tests. The presented investigation aimed at providing an updated information on human leptospirosis burden in Seychelles and exploring the transmission chains in their environmental aspects. Presented data confirms that the disease still heavily impacts the country. Genotyping of pathogenic Leptospira in human acute cases reveals that three distinct Sequence Types (STs) are involved in the disease. However, rats typically considered as the main reservoir in Seychelles, harbor only one of these STs, found only in a minority of human cases. Hence, it appears that rats are likely not the main reservoir of leptospirosis in Seychelles, which has important consequences in terms of preventive measures to be implemented for a better control of human leptospirosis.

Cardiovascular risk status of Afro-origin populations across the spectrum of economic development: findings from the Modeling the Epidemiologic Transition Study

BACKGROUND

Cardiovascular risk factors are increasing in most developing countries. To date, however, very little standardized data has been collected on the primary risk factors across the spectrum of economic development. Data are particularly sparse from Africa.

METHODS

In the Modeling the Epidemiologic Transition Study (METS) we examined population-based samples of men and women, ages 25-45 of African ancestry in metropolitan Chicago, Kingston, Jamaica, rural Ghana, Cape Town, South Africa, and the Seychelles. Key measures of cardiovascular disease risk are described.

RESULTS

The risk factor profile varied widely in both total summary estimates of cardiovascular risk and in the magnitude of component factors. Hypertension ranged from 7% in women from Ghana to 35% in US men. Total cholesterol was well under 200 mg/dl for all groups, with a mean of 155 mg/dl among men in Ghana, South Africa and Jamaica. Among women total cholesterol values varied relatively little by country, following between 160 and 178 mg/dl for all 5 groups. Levels of HDL-C were virtually identical in men and women from all study sites. Obesity ranged from 64% among women in the US to 2% among Ghanaian men, with a roughly corresponding trend in diabetes. Based on the Framingham risk score a clear trend toward higher total risk in association with socioeconomic development was observed among men, while among women there was considerable overlap, with the US participants having only a modestly higher risk score.

CONCLUSIONS

These data provide a comprehensive estimate of cardiovascular risk across a range of countries at differing stages of social and economic development and demonstrate the heterogeneity in the character and degree of emerging cardiovascular risk. Severe hypercholesterolemia, as characteristic in the US and much of Western Europe at the onset of the coronary epidemic, is unlikely to be a feature of the cardiovascular risk profile in these countries in the foreseeable future, suggesting that stroke may remain the dominant cardiovascular event.

Socioeconomic Differences in Dietary Patterns in an East African Country: Evidence from the Republic of Seychelles

BACKGROUND

In high income countries, low socioeconomic status (SES) is related to unhealthier dietary patterns, while evidence on the social patterning of diet in low and middle income countries is scarce.

OBJECTIVE

In this study, we assess dietary patterns in the general population of a middle income country in the African region, the Republic of Seychelles, and examine their distribution according to educational level and income.

METHODS

Data was drawn from two independent national surveys conducted in the Seychelles among adults aged 25-64 years in 2004 (n = 1236) and 2013 (n = 1240). Dietary patterns were assessed by principal component analysis (PCA). Educational level and income were used as SES indicators. Data from both surveys were combined as no interaction was found between SES and year.

RESULTS

Three dietary patterns were identified: "snacks and drinks", "fruit and vegetables" and "fish and rice". No significant associations were found between SES and the "snacks and drinks" pattern. Low vs. high SES individuals had lower adherence to the "fruit and vegetables" pattern [prevalence ratio (95% CI) 0.71 (0.60-0.83)] but a higher adherence to the traditional "fish and rice" pattern [1.58 (1.32-1.88)]. Income modified the association between education and the "fish and rice" pattern (p = 0.02), whereby low income individuals had a higher adherence to this pattern in both educational groups.

CONCLUSION

Low SES individuals have a lower consumption of fruit and vegetables, but a higher consumption of traditional foods like fish and rice. The Seychelles may be at a degenerative diseases stage of the nutrition transition.

Elevated hypertension risk for African-origin populations in biracial societies: modeling the Epidemiologic Transition Study

OBJECTIVES

Blood pressures in persons of African descent exceed those of other racial/ethnic groups in the United States. Whether this trait is attributable to the genetic factors in African-origin populations, or a result of inadequately measured environmental exposures, such as racial discrimination, is not known. To study this question, we conducted a multisite comparative study of communities in the African diaspora, drawn from metropolitan Chicago, Kingston, Jamaica, rural Ghana, Cape Town, South Africa, and the Seychelles.

METHODS

At each site, 500 participants between the age of 25 and 49 years, with approximately equal sex balance, were enrolled for a longitudinal study of energy expenditure and weight gain. In this study, we describe the patterns of blood pressure and hypertension observed at baseline among the sites.

RESULTS

Mean SBP and DBP were very similar in the United States and South Africa in both men and women, although among women, the prevalence of hypertension was higher in the United States (24 vs. 17%, respectively). After adjustment for multiple covariates, relative to participants in the United States, SBP was significantly higher among the South Africans by 9.7 mmHg (P < 0.05) and significantly lower for each of the other sites: for example, Jamaica: -7.9 mmHg (P = 0.06), Ghana: -12.8 mmHg (P < 0.01) and Seychelles: -11.1 mmHg (P = 0.01).

CONCLUSION

These data are consistent with prior findings of a blood pressure gradient in societies of the African diaspora and confirm that African-origin populations with lower social status in multiracial societies, such as the United States and South Africa, experience more hypertension than anticipated based on anthropometric and measurable socioeconomic risk factors.

Seasonal variation of overall and cardiovascular mortality: a study in 19 countries from different geographic locations

Background

Cardiovascular diseases (CVD) mortality has been shown to follow a seasonal pattern. Several studies suggested several possible determinants of this pattern, including misclassification of causes of deaths. We aimed at assessing seasonality in overall, CVD, cancer and non-CVD/non-cancer mortality using data from 19 countries from different latitudes.

Methods and Findings

Monthly mortality data were compiled from 19 countries, amounting to over 54 million deaths. We calculated ratios of the observed to the expected numbers of deaths in the absence of a seasonal pattern. Seasonal variation (peak to nadir difference) for overall and cause-specific (CVD, cancer or non-CVD/non-cancer) mortality was analyzed using the cosinor function model. Mortality from overall, CVD and non-CVD/non-cancer showed a consistent seasonal pattern. In both hemispheres, the number of deaths was higher than expected in winter. In countries close to the Equator the seasonal pattern was considerably lower for mortality from any cause. For CVD mortality, the peak to nadir differences ranged from 0.185 to 0.466 in the Northern Hemisphere, from 0.087 to 0.108 near the Equator, and from 0.219 to 0.409 in the Southern Hemisphere. For cancer mortality, the seasonal variation was nonexistent in most countries.

Conclusions

In countries with seasonal variation, mortality from overall, CVD and non-CVD/non-cancer show a seasonal pattern with mortality being higher in winter than in summer. Conversely, cancer mortality shows no substantial seasonality.

Comparisons of intensity-duration patterns of physical activity in the US, Jamaica and 3 African countries

BACKGROUND

This difference in how populations living in low-, middle or upper-income countries accumulate daily PA, i.e. patterns and intensity, is an important part in addressing the global PA movement. We sought to characterize objective PA in 2,500 participants spanning the epidemiologic transition. The Modeling the Epidemiologic Transition Study (METS) is a longitudinal study, in 5 countries. METS seeks to define the association between physical activity (PA), obesity and CVD risk in populations of African origin: Ghana (GH), South Africa (SA), Seychelles (SEY), Jamaica (JA) and the US (suburban Chicago).

METHODS

Baseline measurements of objective PA, SES, anthropometrics and body composition, were completed on 2,500 men and women, aged 25-45 years. Moderate and vigorous PA (MVPA, min/d) on week and weekend days was explored ecologically, by adiposity status and manual labor.

RESULTS

Among the men, obesity prevalence reflected the level of economic transition and was lowest in GH (1.7%) and SA (4.8%) and highest in the US (41%). SA (55%) and US (65%) women had the highest levels of obesity, compared to only 16% in GH. More men and women in developing countries engaged in manual labor and this was reflected by an almost doubling of measured MPVA among the men in GH (45 min/d) and SA (47 min/d) compared to only 28 min/d in the US. Women in GH (25 min/d), SA (21 min/d), JA (20 min/d) and SEY (20 min/d) accumulated significantly more MPVA than women in the US (14 min/d), yet this difference was not reflected by differences in BMI between SA, JA, SEY and US. Moderate PA constituted the bulk of the PA, with no study populations except SA men accumulating > 5 min/d of vigorous PA. Among the women, no sites accumulated >2 min/d of vigorous PA. Overweight/obese men were 22% less likely to engage in manual occupations.

CONCLUSION

While there is some association for PA with obesity, this relationship is inconsistent across the epidemiologic transition and suggests that PA policy recommendations should be tailored for each environment.

Association of socioeconomic status with overall and cause specific mortality in the Republic of Seychelles: results from a cohort study in the African region

BACKGROUND

Low socioeconomic status (SES) is consistently associated with higher mortality in high income countries. Only few studies have assessed this association in low and middle income countries, mainly because of sparse reliable mortality data. This study explores SES differences in overall and cause-specific mortality in the Seychelles, a rapidly developing small island state in the African region.

METHODS

All deaths have been medically certified over more than two decades. SES and other lifestyle-related risk factors were assessed in a total of 3246 participants from three independent population-based surveys conducted in 1989, 1994 and 2004. Vital status was ascertained using linkage with vital statistics. Occupational position was the indicator of SES used in this study and was assessed with the same questions in the three surveys.

RESULTS

During a mean follow-up of 15.0 years (range 0-23 years), 523 participants died (overall mortality rate 10.8 per 1000 person-years). The main causes of death were cardiovascular disease (CVD) (219 deaths) and cancer (142 deaths). Participants in the low SES group had a higher mortality risk for overall (HR = 1.80; 95% CI: 1.24-2.62), CVD (HR = 1.95; 1.04-3.65) and non-cancer/non-CVD (HR = 2.14; 1.10-4.16) mortality compared to participants in the high SES group. Cancer mortality also tended to be patterned by SES (HR = 1.44; 0.76-2.75). Major lifestyle-related risk factors (smoking, heavy drinking, obesity, diabetes, hypertension, hypercholesterolemia) explained a small proportion of the associations between low SES and all-cause, CVD, and non-cancer/non-CVD mortality.

CONCLUSIONS

In this population-based study assessing social inequalities in mortality in a country of the African region, low SES (as measured by occupational position) was strongly associated with overall, CVD and non-cancer/non-CVD mortality. Our findings support the view that the burden of non-communicable diseases may disproportionally affect people with low SES in low and middle income countries.

Weight status, body image and bullying among adolescents in the Seychelles

We investigated the relationship between being bullied and measured body weight and perceived body weight among adolescents of a middle-income sub Saharan African country. Our data originated from the Global School-based Health Survey, which targets adolescents aged 13–15 years. Student weights and heights were measured before administrating the questionnaire which included questions about personal data, health behaviors and being bullied. Standard criteria were used to assess thinness, overweight and obesity. Among 1,006 participants who had complete data, 16.5% (95%CI 13.3–20.2) reported being bullied ≥3 days during the past 30 days; 13.4% were thin, 16.8% were overweight and 7.6% were obese. Categories of actual weight and of perceived weight correlated only moderately (Spearman correlation coefficient 0.37 for boys and 0.57 for girls; p < 0.001). In univariate analysis, both actual obesity (OR 1.76; p = 0.051) and perception of high weight (OR 1.63 for “slightly overweight”; OR 2.74 for “very overweight”, both p < 0.05) were associated with being bullied. In multivariate analysis, ORs for categories of perceived overweight were virtually unchanged while ORs for actual overweight and obesity were substantially attenuated, suggesting a substantial role of perceived weight in the association with being bullied. Actual underweight and perceived thinness also tended to be associated with being bullied, although not significantly. Our findings suggest that more research attention be given to disentangling the significant association between body image, overweight and bullying among adolescents. Further studies in diverse populations are warranted.

Prevalence of thinness in children and adolescents in the Seychelles: comparison of two international growth references

BACKGROUND

Thinness in children and adolescents is largely under studied, a contrast with abundant literature on under-nutrition in infants and on overweight in children and adolescents. The aim of this study is to compare the prevalence of thinness using two recently developed growth references, among children and adolescents living in the Seychelles, an economically rapidly developing country in the African region.

METHODS

Weight and height were measured every year in all children of 4 grades (age range: 5 to 16 years) of all schools in the Seychelles as part of a routine school-based surveillance program. In this study we used data collected in 16,672 boys and 16,668 girls examined from 1998 to 2004. Thinness was estimated according to two growth references: i) an international survey (IS), defining three grades of thinness corresponding to a BMI of 18.5, 17.0 and 16.0 kg/m2 at age 18 and ii) the WHO reference, defined here as three categories of thinness (-1, -2 and -3 SD of BMI for age) with the second and third named "thinness" and "severe thinness", respectively.

RESULTS

The prevalence of thinness was 21.4%, 6.4% and 2.0% based on the three IS cut-offs and 27.7%, 6.7% and 1.2% based on the WHO cut-offs. The prevalence of thinness categories tended to decrease according to age for both sexes for the IS reference and among girls for the WHO reference.

CONCLUSION

The prevalence of the first category of thinness was larger with the WHO cut-offs than with the IS cut-offs while the prevalence of thinness of "grade 2" and thinness of "grade 3" (IS cut-offs) was similar to the prevalence of "thinness" and "severe thinness" (WHO cut-offs), respectively.

Socioeconomic position and cognitive function in the Seychelles: a life course analysis

OBJECTIVE

Poorer socioeconomic conditions early in life have been linked with memory, attention and learning deficits in adulthood, as well as with specific areas of educational achievement. It remains unclear, however, whether these distal associations are mediated by more current socioeconomic factors. In this study, we sought to confirm the relation between early-life socioeconomic position (SEP) and adult cognitive function, and to examine potential mediation by contemporaneous SEP.

METHODS

Data from 463 young adults from the Main Cohort of the Seychelles Child Development Study were analyzed using subtests of the Cambridge Neurological Test Automated Battery and the Woodcock Johnson Test of Scholastic Achievement in relation to maternal Hollingshead Social Status Index scores at study enrollment (infancy), follow-up at 107 months, and follow-up at 17 years.

RESULTS

Findings include evidence of a link between infant-period SEP and 17-year memory, which was not mediated by childhood and 17-year SEP. Verbal and mathematical achievement at 17 years was associated with SEP at all points in the life course.

CONCLUSIONS

SEP at different points during the young-adult life course may affect different cognitive domains later in life, which may provide targets for societal investment in ensuring adequate family resources throughout childhood and adolescence.

Varying coefficient function models to explore interactions between maternal nutritional status and prenatal methylmercury toxicity in the Seychelles Child Development Nutrition Study

Maternal consumption of fish during the gestational period exposes the fetus to both nutrients, especially the long-chain polyunsaturated fatty acids (LCPUFAs), believed to be beneficial for fetal brain development, as well as to the neurotoxicant methylmercury (MeHg). We recently reported that nutrients present in fish may modify MeHg neurotoxicity. Understanding the apparent interaction of MeHg exposure and nutrients present in fish is complicated by the limitations of modeling methods. In this study we fit varying coefficient function models to data from the Seychelles Child Development Nutrition Study (SCDNS) cohort to assess the association of dietary nutrients and children's development. This cohort of mother-child pairs in the Republic of Seychelles had fish consumption averaging 9 meals per week. Maternal nutritional status was assessed for five different nutritional components known to be present in fish (n-3 LCPUFA, n-6 LCPUFA, iron status, iodine status, and choline) and associated with children's neurological development. We also included prenatal MeHg exposure (measured in maternal hair). We examined two child neurodevelopmental outcomes (Bayley Scales Infant Development-II (BSID-II) Mental Developmental Index (MDI) and Psychomotor Developmental Index (PDI)), each administered at 9 and at 30 months. The varying coefficient models allow the possible interactions between each nutritional component and MeHg to be modeled as a smoothly varying function of MeHg as an effect modifier. Iron, iodine, choline, and n-6 LCPUFA had little or no observable modulation at different MeHg exposures. In contrast the n-3 LCPUFA docosahexaenoic acid (DHA) had beneficial effects on the BSID-II PDI that were reduced or absent at higher MeHg exposures. This study presents a useful modeling method that can be brought to bear on questions involving interactions between covariates, and illustrates the continuing importance of viewing fish consumption during pregnancy as a case of multiple exposures to nutrients and to MeHg. The results encourage more emphasis on a holistic view of the risks and benefits of fish consumption as it relates to infant development.

Fish consumption, mercury exposure, and their associations with scholastic achievement in the Seychelles Child Development Study

Studies of neurodevelopmental outcomes in offspring exposed to MeHg from maternal consumption of fish have primarily measured cognitive abilities. Reported associations have been subtle and in both adverse and beneficial directions. Changes in functional outcomes such as school achievement and behavior in exposed children and adolescents have not been examined. We undertook an assessment of school success of children in the Seychelles Child Development Study (SCDS) main cohort to determine if there were any associations with either prenatal or recent postnatal MeHg exposure. The primary endpoints were Seychelles nationally standardized end-of-year examinations given when the cohort children were 9 and 17 years of age. A subgroup (n=215) from the main cohort was also examined at 9 years of age using a regional achievement test called SACMEQ. Prenatal MeHg exposure was 6.8 ppm in maternal hair; recent postnatal exposure was 6.09 ppm at 9 years and 8.0 ppm at 17 years, measured in child hair. Multiple linear regression analyses showed no pattern of associations between prenatal or postnatal exposure, and either the 9- or 17-year end-of-year examination scores. For the subgroup of 215 subjects who participated in the SACMEQ test, there were significant adverse associations between examination scores and postnatal exposure, but only for males. The average postnatal exposure level in child hair for this subgroup was significantly higher than for the overall cohort. These results are consistent with our earlier studies and support the interpretation that prenatal MeHg exposure at dosages achieved by mothers consuming a diet high in fish are not associated with adverse educational measures of scholastic achievement. The adverse association of educational measures with postnatal exposure in males is intriguing, but will need to be confirmed by further studies examining factors that influence scholastic achievement.

Iron status in pregnant women in the Republic of Seychelles

OBJECTIVE

To establish the Fe status of pregnant women and their neonates in the Republic of Seychelles.

DESIGN

A prospective study.

SETTING

Republic of Seychelles.

SUBJECTS

Pregnant women were recruited and blood samples taken at enrolment and post-delivery along with cord blood samples. Ferritin and soluble transferrin receptor (sTfR) were measured in maternal (n 220) and cord blood (n 123) samples.

RESULTS

Maternal Fe deficiency (ferritin < 15 ng/ml, sTfR > 28 nmol/l) was present in 6 % of subjects at enrolment and in 20 % at delivery. There was no significant decrease in maternal ferritin. A significant increase in sTfR was observed between enrolment and delivery (P < 0.001). Maternal BMI and use of Fe supplements at 28 weeks' gestation were associated with improved maternal Fe status at delivery, whereas parity had a negative effect on sTfR and ferritin at delivery.

CONCLUSIONS

Fe status of pregnant Seychellois women was, on average, within normal ranges. The incidence of Fe deficiency throughout pregnancy in this population was similar to that in a Westernised population. Increased awareness of the importance of adequate Fe intake during pregnancy, particularly in multiparous women, is warranted.

Interpreting epidemiological evidence in the presence of multiple endpoints: an alternative analytic approach using the 9-year follow-up of the Seychelles child development study

PURPOSE

The potential for ill-informed causal inference is a major concern in published longitudinal studies evaluating impaired neurological function in children prenatally exposed to background levels of methyl mercury (MeHg). These studies evaluate a large number of developmental tests. We propose an alternative analysis strategy that reduces the number of comparisons tested in these studies.

METHODS

Using data from the 9-year follow-up of 643 children in the Seychelles child development study, we grouped 18 individual endpoints into one overall ordinal outcome variable as well as by developmental domains. Subsequently, ordinal logistic regression analyses were performed.

RESULTS

We did not find an association between prenatal MeHg exposure and developmental outcomes at 9 years of age.

CONCLUSION

Our proposed framework is more likely to result in a balanced interpretation of a posteriori associations. In addition, this new strategy should facilitate the use of complex epidemiological data in quantitative risk assessment.

Associations of maternal long-chain polyunsaturated fatty acids, methyl mercury, and infant development in the Seychelles Child Development Nutrition Study

Fish consumption during gestation can provide the fetus with long-chain polyunsaturated fatty acids (LCPUFA) and other nutrients essential for growth and development of the brain. However, fish consumption also exposes the fetus to the neurotoxicant, methyl mercury (MeHg). We studied the association between these fetal exposures and early child development in the Seychelles Child Development Nutrition Study (SCDNS). Specifically, we examined a priori models of Omega-3 and Omega-6 LCPUFA measures in maternal serum to test the hypothesis that these LCPUFA families before or after adjusting for prenatal MeHg exposure would reveal associations with child development assessed by the BSID-II at ages 9 and 30 months. There were 229 children with complete outcome and covariate data available for analysis. At 9 months, the PDI was positively associated with total Omega-3 LCPUFA and negatively associated with the ratio of Omega-6/Omega-3 LCPUFA. These associations were stronger in models adjusted for prenatal MeHg exposure. Secondary models suggested that the MeHg effect at 9 months varied by the ratio of Omega-6/Omega-3 LCPUFA. There were no significant associations between LCPUFA measures and the PDI at 30 months. There were significant adverse associations, however, between prenatal MeHg and the 30-month PDI when the LCPUFA measures were included in the regression analysis. The BSID-II mental developmental index (MDI) was not associated with any exposure variable. These data support the potential importance to child development of prenatal availability of Omega-3 LCPUFA present in fish and of LCPUFA in the overall diet. Furthermore, they indicate that the beneficial effects of LCPUFA can obscure the determination of adverse effects of prenatal MeHg exposure in longitudinal observational studies.

Associations of maternal long-chain polyunsaturated fatty acids, methyl mercury, and infant development in the Seychelles Child Development Nutrition Study

Fish consumption during gestation can provide the fetus with long-chain polyunsaturated fatty acids (LCPUFA) and other nutrients essential for growth and development of the brain. However, fish consumption also exposes the fetus to the neurotoxicant, methyl mercury (MeHg). We studied the association between these fetal exposures and early child development in the Seychelles Child Development Nutrition Study (SCDNS). Specifically, we examined a priori models of Omega-3 and Omega-6 LCPUFA measures in maternal serum to test the hypothesis that these LCPUFA families before or after adjusting for prenatal MeHg exposure would reveal associations with child development assessed by the BSID-II at ages 9 and 30 months. There were 229 children with complete outcome and covariate data available for analysis. At 9 months, the PDI was positively associated with total Omega-3 LCPUFA and negatively associated with the ratio of Omega-6/Omega-3 LCPUFA. These associations were stronger in models adjusted for prenatal MeHg exposure. Secondary models suggested that the MeHg effect at 9 months varied by the ratio of Omega-6/Omega-3 LCPUFA. There were no significant associations between LCPUFA measures and the PDI at 30 months. There were significant adverse associations, however, between prenatal MeHg and the 30-month PDI when the LCPUFA measures were included in the regression analysis. The BSID-II mental developmental index (MDI) was not associated with any exposure variable. These data support the potential importance to child development of prenatal availability of Omega-3 LCPUFA present in fish and of LCPUFA in the overall diet. Furthermore, they indicate that the beneficial effects of LCPUFA can obscure the determination of adverse effects of prenatal MeHg exposure in longitudinal observational studies.

Decreasing Association Between Body Mass Index and Blood Pressure Over Time

BACKGROUND

Our purpose was to assess blood pressure (BP) and its relationship with body mass index (BMI) over a 15-year interval in the Seychelles, a rapidly developing country in the African region.

METHODS

Two independent cross-sectional examination surveys were conducted in 1989 (n=1081) and 2004 (n=1255) using representative samples of the population age 25-64 years.

RESULTS

Between 1989 and 2004, mean BP (mm Hg) decreased slightly (from 133/87 to 131/86 in men and from 127/82 to 124/81 in women), with little change in the age-standardized prevalence of high BP (BP >or=140/90 or current treatment; from 45% to 44% in men and from 34% to 36% in women). During this same time period, there were marked increases in awareness (from 42% to 64%), treatment (22% to 59%), and control (3% to 20%) among participants with high BP. The prevalence of overweight (BMI >or=25 kg/m) increased from 39% to 60%. Furthermore, the linear relationship between BMI and BP was markedly weaker in 2004 than in 1989, irrespective of antihypertensive treatment and age, and among both lean and overweight participants. Among untreated persons, a BMI increment of 1 kg/m was associated with an elevation of 2.0/1.5 mm Hg of systolic/diastolic BP in 1989 but only 1.3/1.0 mm Hg in 2004.

CONCLUSIONS

The association between BMI and BP has decreased over time. Further study is needed to understand the reasons for the decline in this association, and what the implications are in the context of the obesity epidemic.

HIV type 1 diversity in the Seychelles

Subtype determination and drug resistance-associated mutations (DRM) detection were performed on 40 HIV-1 Western blot-positive sera detected, obtained from consecutive patients resident in the Seychelles and consulting the Communicable Disease Control Unit, HIV reference center, in Victoria Hospital (Mahe) from October 2005 to June 2006. Amplification and sequencing of at least two of the partial reverse transcriptase, protease, and partial envelope genes were successful for all strains. All three genes sequences were obtained for 39 strains. A high degree of subtype or circulating recombinant forms (CRF) was observed for these 39 strains: A-A1 (17 cases), C (10 cases), B (8 cases), CRF02_AG (2 cases), D (1 case) and CRF01_AE (1 case). According to the ANRS 2006 DRM list and algorithm, none of the 40 isolates was found to be resistant to any protease or reverse transcriptase inhibitors.

Dose-response relationship of prenatal mercury exposure and IQ: an integrative analysis of epidemiologic data

BACKGROUND

Prenatal exposure to mercury has been associated with adverse childhood neurologic outcomes in epidemiologic studies. Dose-response information for this relationship is useful for estimating benefits of reduced mercury exposure.

OBJECTIVES

We estimated a dose-response relationship between maternal mercury body burden and subsequent childhood decrements in intelligence quotient (IQ), using a Bayesian hierarchical model to integrate data from three epidemiologic studies.

METHODS

Inputs to the model consist of dose-response coefficients from studies conducted in the Faroe Islands, New Zealand, and the Seychelles Islands. IQ coefficients were available from previous work for the latter two studies, and a coefficient for the Faroe Islands study was estimated from three IQ subtests. Other tests of cognition/achievement were included in the hierarchical model to obtain more accurate estimates of study-to-study and end point-to-end point variability.

RESULTS

We find a central estimate of -0.18 IQ points (95% confidence interval, -0.378 to -0.009) for each parts per million increase of maternal hair mercury, similar to the estimates for both the Faroe Islands and Seychelles studies, and lower in magnitude than the estimate for the New Zealand study. Sensitivity analyses produce similar results, with the IQ coefficient central estimate ranging from -0.13 to -0.25.

CONCLUSIONS

IQ is a useful end point for estimating neurodevelopmental effects, but may not fully represent cognitive deficits associated with mercury exposure, and does not represent deficits related to attention and motor skills. Nevertheless, the integrated IQ coefficient provides a more robust description of the dose-response relationship for prenatal mercury exposure and cognitive functioning than results of any single study.

Prenatal methyl mercury exposure from fish consumption and child development: A review of evidence and perspectives from the Seychelles Child Development Study

Evidence from an outbreak of methyl mercury (MeHg) poisoning in Iraq suggested that adverse effects of prenatal exposure on child development begin to appear at or above 10ppm measured in maternal hair. To test this hypothesis in a fish-eating population, we enrolled a cohort of 779 children (the main cohort) in the Seychelles Child Development Study (SCDS). The cohort was prenatally exposed to MeHg from maternal fish consumption, and the children started consuming fish products at about 1 year of age. Prenatal exposure was measured in maternal hair and recent postnatal exposure in the child's hair. The cohort has been examined six times over 11 years using extensive batteries of age-appropriate developmental tests. Analyses of a large number of developmental outcomes have identified frequent significant associations in the appropriate direction with numerous covariates known to affect child development, but only one adverse association between prenatal MeHg exposure and a developmental endpoint. Because such results could be ascribed to chance, there is no convincing evidence for an association between prenatal exposure and child development in this fish-eating population. Secondary analyses have generally supported the primary analyses, but more recently have suggested that latent or delayed adverse effects might be emerging at exposure above 10-12ppm as the children mature. This suggests that the association between prenatal exposure and child development may be more complex than originally believed. This paper reviews the SCDS main cohort study results and presents our current interpretations.

Prevalence of elevated blood pressure and association with overweight in children of a rapidly developing country

We assessed the prevalence of elevated blood pressure (BP) and the association with excess body weight among a large sample of children in the Seychelles, a middle-income rapidly developing country in the African region. Weight, height and BP were measured in all children of four school grades in the Seychelles (Indian Ocean). Excess weight categories ('overweight' and 'obesity') were defined according to the criteria of the International Obesity Task Force. Two BP readings were obtained on one occasion. 'Elevated BP' was defined based on US reference tables. Data were available in 15,612 (86%) of 18,119 eligible children aged 5-16 years in 2002-2004. In all, 13.0% of Boys and 18.8% of girls were overweight or obese. The prevalence of elevated BP was 9.1% in boys and 10.1% in girls. Both systolic and diastolic BP were strongly associated with body mass index (BMI) in boys and in girls. In children with 'normal weight', 'overweight (and not obesity)' and 'obesity', respectively, proportions with elevated BP were 7.5, 16.9 and 25.2% in boys, and 7.5, 16.1 and 33.2% in girls. Overweight (including obesity) could account for 18% of cases of elevated BP in boys and 26% in girls. Further studies should examine the impact of the relationship between BMI and elevated BP on the burden of hypertension in the context of the epidemic of paediatric obesity.

Clustering of smoking, alcohol drinking and cannabis use in adolescents in a rapidly developing country

BACKGROUND

Smoking, alcohol drinking and cannabis use ("risk behaviors") are often initiated at a young age but few epidemiological studies have assessed their joined prevalence in children in developing countries. This study aims at examining the joint prevalence of these behaviors in adolescents in the Seychelles, a rapidly developing country in the Indian Ocean.

METHODS

Cross-sectional survey in a representative sample of secondary school students using an anonymous self-administered questionnaire (Global Youth Tobacco Survey). The questionnaire was completed by 1,321 (92%) of 1,442 eligible students aged 11 to 17 years. Main variables of interest included smoking cigarettes on > or =1 day in the past 30 days; drinking any alcohol beverage on > or =1 day in the past 30 days and using cannabis at least once in the past 12 months.

RESULTS

In boys and girls, respectively, prevalence (95% CI) was 30% (26-34)/21% (18-25) for smoking, 49% (45-54)/48% (43-52) for drinking, and 17% (15-20)/8% (6-10) for cannabis use. The prevalence of all these behaviors increased with age. Smokers were two times more likely than non-smokers to drink and nine times more likely to use cannabis. Drinkers were three times more likely than non-drinkers to smoke or to use cannabis. Comparison of observed versus expected frequencies of combination categories demonstrated clustering of these risk behaviors in students (P < 0.001).

CONCLUSION

Smoking, drinking and cannabis use were common and clustered among adolescents of a rapidly developing country. These findings stress the need for early and integrated prevention programs.

Plasma aldosterone is independently associated with the metabolic syndrome

The aim of this study was to analyze the associations of plasma aldosterone and plasma renin activity with the metabolic syndrome and each of its components. We analyzed data from a family based study in the Seychelles made up of 356 participants (160 men and 196 women) from 69 families of African descent. In multivariable models, plasma aldosterone was associated positively (P < 0.05) with blood pressure in older individuals (interaction with age, P < 0.05) and with waist circumference in men (interaction with sex, P < 0.05) and negatively with high-density lipoprotein cholesterol, in particular in individuals with elevated urinary potassium excretion (interaction with urinary potassium, P < 0.05); plasma renin activity was significantly associated with triglycerides and fasting blood glucose. Plasma aldosterone, but not plasma renin activity, was associated with the metabolic syndrome per se, independently of the association with its separate components. The observation that plasma renin activity was associated with some components of the metabolic syndrome, whereas plasma aldosterone was associated with other components of the metabolic syndrome, suggests different underlying mechanisms. These findings reinforce previous observations suggesting that aldosterone is associated with several cardiovascular risk factors and also suggest that aldosterone might contribute to the increased cardiovascular disease risk in individuals of African descent with the metabolic syndrome.

Benchmark concentrations for methyl mercury obtained from the 9-year follow-up of the Seychelles Child Development Study

Methyl mercury (MeHg) is highly toxic to the developing nervous system. Human exposure is mainly from fish consumption since small amounts are present in all fish. Findings of developmental neurotoxicity following high-level prenatal exposure to MeHg raised the question of whether children whose mothers consumed fish contaminated with background levels during pregnancy are at an increased risk of impaired neurological function. Benchmark doses determined from studies in New Zealand, and the Faroese and Seychelles Islands indicate that a level of 4-25 parts per million (ppm) measured in maternal hair may carry a risk to the infant. However, there are numerous sources of uncertainty that could affect the derivation of benchmark doses, and it is crucial to continue to investigate the most appropriate derivation of safe consumption levels. Earlier, we published the findings from benchmark analyses applied to the data collected on the Seychelles main cohort at the 66-month follow-up period. Here, we expand on the main cohort analyses by determining the benchmark doses (BMD) of MeHg level in maternal hair based on 643 Seychellois children for whom 26 different neurobehavioral endpoints were measured at 9 years of age. Dose-response models applied to these continuous endpoints incorporated a variety of covariates and included the k-power model, the Weibull model, and the logistic model. The average 95% lower confidence limit of the BMD (BMDL) across all 26 endpoints varied from 20.1 ppm (range=17.2-22.5) for the logistic model to 20.4 ppm (range=17.9-23.0) for the k-power model. These estimates are somewhat lower than those obtained after 66 months of follow-up. The Seychelles Child Development Study continues to provide a firm scientific basis for the derivation of safe levels of MeHg consumption.

[Epidemiology and prevention of malaria in the southwestern islands of the Indian Ocean]

Malaria epidemiology differs greatly in the geographically close islands of the southwestern Indian Ocean. In Madagascar and the Comoros Union malaria is still a major public health problem. In Mayotte indigenous transmission resumed in 1995 and is currently high in some communities. In the Mascarene Islands (Reunion and Mauritius), indigenous transmission has been eradicated (Reunion) or become rare (Mauritius). The Seychelles Islands are malaria-free since local conditions are unfavorable for Anopheles mosquitoes. The level of resistance to antimalarials also differs from one island to another. Resistance to chloroquine ranges from moderate in Madagascar to high in the Comoros Union. Health recommendations for travelers must be adapted to the epidemiological features on each island.

[Chikungunya on Reunion Island: chronicle of an epidemic foretold]

Chikungunya is a viral disease transmitted by a mosquito of the genus Aedes. It is currently epidemic on Reunion Island, in the Indian Ocean. It is essentially characterized by an influenza syndrome but associated with polyarthralgia and an eruption. The disabling and chronic nature of the arthralgia is the most remarkable clinical aspect of chikungunya infection. Severe and unusual forms have appeared, not previously described in the literature. These forms must be studied to determine whether there is a direct relation between the chikungunya virus and the severity factors. Treatment is solely symptomatic, combining analgesic and/or antiinflammatory agents. There is no vaccine. The epidemic is not limited to Reunion: cases of chikungunya have also been reported in neighboring islands (Maurice, Seychelles, and Madagascar). Travelers planning to visit the region should be counseled.

Comparison of smoking, drinking, and marijuana use between students present or absent on the day of a school-based survey

The aim of this population-based survey was to compare the prevalence of selected risk behaviors between students present or absent on the day of a school-based survey. The study population was a representative sample of all students of secondary schools in the Seychelles (Indian Ocean). Students absent on the day of the survey were traced and requested to complete the same self-administered questionnaire as did present students. Self-reported consumption of cigarettes, alcohol, and marijuana were measured. Of the sample of 1453 eligible students aged 11 to 17 years, 1321 "present students" completed the survey (90.9% participation), 11 refused to answer all questions, and 121 were not present at school. We could trace 105 of the 121 students not present at school on the survey day ("absent students"), and all of them completed the questionnaire over the next 4 weeks. The prevalence of risk behaviors was significantly higher in absent than present students for current smoking and drinking. Inclusion of data from the absent students resulted in a relative increase in the prevalence of the considered behaviors by 3% to 8% as compared to data based on present students only. In conclusion, the prevalence of risk behaviors was higher in absent than present students. Adjusting for data of absent students increased the prevalence estimates in the base population.

Prevalence of cardiovascular risk factors in a middle-income country and estimated cost of a treatment strategy

Background

We assessed the prevalence of risk factors for cardiovascular disease (CVD) in a middle-income country in rapid epidemiological transition and estimated direct costs for treating all individuals at increased cardiovascular risk, i.e. following the so-called "high risk strategy".

Methods

Survey of risk factors using an age- and sex-stratified random sample of the population of Seychelles aged 25–64 in 2004. Assessment of CVD risk and treatment modalities were in line with international guidelines. Costs are expressed as US$ per capita per year.

Results

1255 persons took part in the survey (participation rate of 80.2%). Prevalence of main risk factors was: 39.6% for high blood pressure (≥140/90 mmHg or treatment) of which 59% were under treatment; 24.2% for high cholesterol (≥6.2 mmol/l); 20.8% for low HDL-cholesterol (<1.0 mmol/l); 9.3% for diabetes (fasting glucose ≥7.0 mmol/l); 17.5% for smoking; 25.1% for obesity (body mass index ≥30 kg/m²) and 22.1% for the metabolic syndrome. Overall, 43% had HBP, high cholesterol or diabetes and substantially increased CVD risk. The cost for medications needed to treat all high-risk individuals amounted to US $45.6, i.e. $11.2 for high blood pressure, $3.8 for diabetes, and $30.6 for dyslipidemia (using generic drugs except for hypercholesterolemia). Cost for minimal follow-up medical care and laboratory tests amounted to $22.6.

Conclusion

High prevalence of major risk factors was found in a rapidly developing country and costs for treatment needed to reduce risk factors in all high-risk individuals exceeded resources generally available in low or middle income countries. Our findings emphasize the need for affordable cost-effective treatment strategies and the critical importance of population strategies aimed at reducing risk factors in the entire population.

Marked increase in the prevalence of obesity in children of the Seychelles, a rapidly developing country, between 1998 and 2004

BACKGROUND

There are few data on overweight in children in developing countries. Such data are important to guide public health policy. We assessed trends in the prevalence of overweight and obesity in children from the Seychelles, a middle-income island state in the Indian Ocean.

METHODS

Multiple cross-sectional surveys were conducted each year between 1998 and 2004 on all students of all schools in four selected school grades (creche, 4th, 7th and 10th years of mandatory school). Weight and height were measured and children were asked about walking time and frequency of physical exercise at leisure time. Excess weight categories were defined according to the criteria of the International Obesity Task Force (IOTF) and the U.S. Centers for Disease Control and Prevention (CDC).

RESULTS

Data were available for 33 340 observations in 1998-2004, corresponding to 23,459 individual children measured once or several times. Based on IOTF criteria, the prevalence of 'overweight' or 'obesity' increased from 8.7% to 13.5% in boys, and from 11.8% to 18.6% in girls from 1998 to 2004 (P < 0.001). The prevalence of 'obesity' increased from 2.1% to 5.2% in boys and from 3.1% to 6.2% in girls (P < 0.001). Using CDC criteria, the prevalence of 'at risk of overweight' and 'overweight' increased by similar proportions. The shift towards higher values over time was larger in the upper than the lower tail of the BMI distribution. Physical activity decreased over calendar years and was inversely associated with excess weight.

CONCLUSIONS

The prevalence of excess weight increased markedly over a seven-year period in children in the Seychelles. This is likely to reflect a rapid nutrition transition with increasingly positive energy balance. These findings stress the need for programs and policies aimed at promoting physical activity and healthy nutrition in countries in epidemiological transition.

[Neurodevelopmental effects from prenatal exposure to methylmercury in the Seychellois and Faroes cohorts and the critical concentration: a review]

A workshop on the Scientific Issues Relevant to Assessment of Health Effects from Exposure to Methylmercury was held in Raleigh, North Carolina, November 18-20, 1998. At that time, most discussions focused on two of the major epidemiologic studies, e.g., Seychelles child development study and Faroese birth cohort study, associating methylmercury exposure with an array of developmental measures in children. These two studies seemed to provide different conclusions on the potential health effects of methylmercury and significant uncertainties remained because of issues related to exposure, neurobehavioral endpoints, confounders and statistics, and design. Since then, each group researching the Seychellois or Faroes cohort has reported some new findings on the risk assessment of methylmercury. This article is intended to present an overview of the above research, as well as benchmark dose calculations. One implication is that neuropsychological measures may depend on social and cultural factors including race and language, and another is that a key to resolve whether the exposure has harmed the fetus appears to lie in neurophysiological measures such as brainstem auditory evoked potentials and electrocardiographic R-R interval variability. In addition, it is likely that the findings published tend to underestimate the neurotoxic effects of developmental methylmercury exposure. In light of the precautionary principle, a conclusion on health effects of low-level dietary exposures to methylmercury needs to be drawn from all available data including the New Zealand study.

Patients' sibling history was sensitive for hypertension and specific for diabetes

OBJECTIVE

We examined the analytic validity of reported family history of hypertension and diabetes among siblings in the Seychelles.

STUDY DESIGN AND SETTING

Four hundred four siblings from 73 families with at least two hypertensive persons were identified through a national hypertension register. Two gold standards were used prospectively. Sensitivity was the proportion of respondents who indicated the presence of disease in a sibling, given that the sibling reported to be affected (personal history gold standard) or was clinically affected (clinical status gold standard). Specificity was the proportion of respondents who reported an unaffected sibling, given that the sibling reported to be unaffected or was clinically unaffected. Respondents gave information on the disease status in their siblings in approximately two-thirds of instances.

RESULTS

When sibling history could be obtained (n=348 for hypertension, n=404 for diabetes), the sensitivity and the specificity of the sibling history were, respectively, 90 and 55% for hypertension, and 61 and 98% for diabetes, using clinical status and, respectively, 89 and 78% for hypertension, and 53 and 98% for diabetes, using personal history.

CONCLUSION

The sibling history, when available, is a useful screening test to detect hypertension, but it is less useful to detect diabetes.

Prevalence of hyperuricemia and relation of serum uric acid with cardiovascular risk factors in a developing country

BACKGROUND

The prevalence of hyperuricemia has rarely been investigated in developing countries. The purpose of the present study was to investigate the prevalence of hyperuricemia and the association between uric acid levels and the various cardiovascular risk factors in a developing country with high average blood pressures (the Seychelles, Indian Ocean, population mainly of African origin).

METHODS

This cross-sectional health examination survey was based on a population random sample from the Seychelles. It included 1011 subjects aged 25 to 64 years. Blood pressure (BP), body mass index (BMI), waist circumference, waist-to-hip ratio, total and HDL cholesterol, serum triglycerides and serum uric acid were measured. Data were analyzed using scatterplot smoothing techniques and gender-specific linear regression models.

RESULTS

The prevalence of a serum uric acid level >420 micromol/L in men was 35.2% and the prevalence of a serum uric acid level >360 micromol/L was 8.7% in women. Serum uric acid was strongly related to serum triglycerides in men as well as in women (r = 0.73 in men and r = 0.59 in women, p < 0.001). Uric acid levels were also significantly associated but to a lesser degree with age, BMI, blood pressure, alcohol and the use of antihypertensive therapy. In a regression model, triglycerides, age, BMI, antihypertensive therapy and alcohol consumption accounted for about 50% (R2) of the serum uric acid variations in men as well as in women.

CONCLUSIONS

This study shows that the prevalence of hyperuricemia can be high in a developing country such as the Seychelles. Besides alcohol consumption and the use of antihypertensive therapy, mainly diuretics, serum uric acid is markedly associated with parameters of the metabolic syndrome, in particular serum triglycerides. Considering the growing incidence of obesity and metabolic syndrome worldwide and the potential link between hyperuricemia and cardiovascular complications, more emphasis should be put on the evolving prevalence of hyperuricemia in developing countries.

Do recent data from the Seychelles Islands alter the conclusions of the NRC Report on the toxicological effects of methylmercury?

In 2000, the National Research Council (NRC), an arm of the National Academy of Sciences, released a report entitled, "Toxicological Effects of Methylmercury." The overall conclusion of that report was that, at levels of exposure in some fish- and marine mammal-consuming communities (including those in the Faroe Islands and New Zealand), subtle but significant adverse effects on neuropsychological development were occurring as a result of in utero exposure. Since the release of that report, there has been continuing discussion of the public health relevance of current levels of exposure to Methylmercury. Much of this discussion has been linked to the release of the most recent longitudinal update of the Seychelles Island study. It has recently been posited that these findings supercede those of the NRC committee, and that based on the Seychelles findings, there is little or no risk of adverse neurodevelopmental effects at current levels of exposure. In this commentary, members of the NRC committee address the conclusions from the NRC report in light of the recent Seychelles data. We conclude that no evidence has emerged since the publication of the NRC report that alters the findings of that report.

Developmental neurotoxicity following prenatal exposures to methylmercury and PCBs in humans from epidemiological studies

Adverse health effects following prenatal exposures to methylmercury (MeHg) have been apparent from several prospective cohort studies conducted in a fish-eating population. A prospective study in a Faroese birth cohort documented subtle deficits of several functional domains at prenatal MeHg exposure levels previously thought to be safe. Recent additional studies also showed neurobehavioral deficits associated with exposures to polychlorinated biphenyls (PCBs) with concomitant MeHg poisoning. In contrast, a prospective study in the Seychelles did not detect a similar association between MeHg exposure and neurodevelopmental deficits; children of the highest MeHg exposure group showed better scores in some developmental tests than those of the lower exposure groups for both prenatal and postnatal MeHg exposures. This paradoxical difference between both studies is summarized herein. The primary source of human exposure to MeHg is fish. Since a considerable number of pollutants, including polychlorinated biphenyls (PCBs) and pesticides, are also present in fish, and since some organochemical substances including PCBs are also well documented to be neurotoxic to the developing brain from epidemiological studies, the combined effects of these pollutants should be considered in discussing the neurotoxicity of MeHg. In this article, therefore, major prospective cohort studies focusing on the exposures to PCBs were reviewed.

Prevalence and risk factors for overweight and obesity in children from Seychelles, a country in rapid transition: the importance of early growth

OBJECTIVES

To establish the prevalence of overweight and obesity and related risk factors in children from Seychelles (Indian Ocean), a country in rapid economic and epidemiological transition.

DESIGN

Cross-sectional study with retrospective access to early life data.

SUBJECTS

All children from all schools of Seychelles, in four selected school grades (kindergarten, fourth, seventh and tenth year of obligatory school) in 1999. A total of 5514 children aged 4.5-17.4 y were measured, corresponding to 83.5% of the eligible population.

MEASUREMENTS

Overweight and obesity, using age- and sex-specific body mass index (BMI) cut-off points as defined by the International Obesity Task Force.

RESULTS

Some 12.6% (95% confidence interval: 11.8-13.5%) of the children were overweight and 3.8% (3.3-4.4%) were obese. Weight gain (kg) during the first year of life was strongly associated with subsequent overweight (odds ratio 1.46, 95% confidence interval 1.27-1.67) and obesity (1.59, 1.29-1.97) in childhood, independently of birth weight. Increased maternal BMI (kg/m(2)) was also associated with overweight (1.07, 1.03-1.10) and obesity (1.09, 1.04-1.14) in the offspring.

CONCLUSION

Prevalence of overweight and obesity among school children in Seychelles was as high as or higher than in some industrialized countries. If confirmed in other environments, the strong association between weight gain during the first year of life and subsequent obesity in childhood could affect the way optimal infant weight gain is defined in countries where public health priorities are changing.

Body mass index, abdominal adiposity and blood pressure: consistency of their association across developing and developed countries

BACKGROUND

Obesity is increasing worldwide because developing countries are adopting Western high-fat foods and sedentary lifestyles. In parallel, in many of them, hypertension is rising more rapidly, particularly with age, than in Western countries.

OBJECTIVE

To assess the relationship between adiposity and blood pressure (BP) in a developing country with high average BP (The Seychelles, Indian Ocean, population mainly of African origin) in comparison to a developed country with low average BP (Switzerland, population mainly of Caucasian origin).

DESIGN

Cross-sectional health examination surveys based on population random samples.

SETTING

The main Seychelles island (Mahé) and two Swiss regions (Vaud-Fribourg and Ticino).

SUBJECTS

Three thousand one hundred and sixteen adults (age range 35-64) untreated for hypertension.

MEASUREMENTS

Body mass index (BMI), waist circumference (WC), waist-to-hip ratio (WHR), systolic and diastolic blood pressure (SBP and DBP, mean of two measures).

METHODS

Scatterplot smoothing techniques and gender-specific linear regression models.

RESULTS

On average, SBP and DBP were found to increase linearly over the whole variation range of BMI, WHR and WC. A modest, but statistically significant linear association was found between each indicator of adiposity and BP levels in separate regression models controlling for age. The regression coefficients were not significantly different between the Seychelles and the two Swiss regions, but were generally higher in women than in men. For the latter, a gain of 1.7 kg/m(2) in BMI, of 4.5 cm in WC or of 3.4% in WHR corresponded to an elevation of 1 mmHg in SBP. For women, corresponding figures were 1.25 kg/m(2), 2.5 cm and 1.8% respectively. Regression coefficients for age reflected a higher effect of this variable on both SBP and DBP in the Seychelles than in Switzerland.

CONCLUSION

These findings suggest a stable linear relation of adiposity with BP, independent of age and body fat distribution, across developed and developing countries. The more rapid increase of BP with age observed in the latter countries are likely to reflect higher genetic susceptibility and/or higher cumulative exposure to another risk factor than adiposity.

Monitoring one-year compliance to antihypertension medication in the Seychelles

OBJECTIVE

To examine the compliance to medication among newly diagnosed hypertensive patients screened from the general population of the Seychelles, a rapidly developing country.

METHODS

Among the 1067 participants to a population-based survey for cardiovascular risk factors, hypertension was discovered in 50 (previously unaware of having hypertension and having blood pressure > or = 160/95 mmHg over 3 visits). These 50 patients were placed on a daily one-pill regimen of medication (bendrofluazide, atenolol, or a combination of hydrochlorothiazide and atenolol) and compliance to the regimen was assessed over 12 months using electronic pill containers. Satisfactory compliance was defined as taking the medication on 6 or 7 days a week on average (which corresponds to a mean compliance level of > or = 86%).

FINDINGS

In the first month, fewer than half (46%) of the new hypertension patients achieved satisfactory compliance, and only about one-quarter (26%) achieved this level by the twelfth month. Compliance was better among the 23 participants who regularly attended medical follow-up, with nearly three-quarters of these patients (74%) achieving satisfactory compliance during the first month and over one-half (55%) by the twelfth month. There was a direct association between mean 12-month compliance level and having a highly skilled occupation; having good health awareness; and regularly attending medical appointments. In contrast, there was an inverse relationship between mean compliance level and heavy drinking.

CONCLUSION

The low proportion of people selected from the general population who were capable of sustaining satisfactory compliance to antihypertension medication may correspond to the maximum effectiveness of medication interventions based on a screening and treatment strategy in the general population. The results stress the need for both high-risk and population approaches to improve hypertension control.