Weight threshold and blood pressure in a lean black population

Blood pressure screening in Mata Sector, a rural area of Rwanda

In rural sub-Saharan Africa, knowledge of non-communicable diseases such as high blood pressure (BP) is rather limited. This report provides information about a BP screening in Mata Sector, a rural region in Southern Province of Rwanda. Community-based, house-to-house screening was performed between February and July 2020 on more than 7000 inhabitants. The screening was conducted by a local team composed by 20 community health care workers, five community health care supervisors, and one nurse with hypertension surveillance training. BP and heart rate were recorded after 5 min of resting, using a validated automated oscillometric OMRON M6 IT-HEM-7322-E monitor with Intelli Wrap Cuff (HEM-FL31-E) technology. The mean of the second and third value was retained. BP was normal (<140/90 mm Hg) in 6340 (88%) and elevated in 863 (12%) participants with 95% of unawareness. Grade 1 (140-159/90-99 mm Hg) hypertensive BP readings were detected in 697 (81%), grade 2 (160-179/100-109 mm Hg) in 134 (16%), and grade 3 (≥180/≥110 mm Hg) in 32 (3.7%) individuals. The prevalence of hypertensive readings was significantly age-dependent. Additionally, a slightly greater proportion of participants with high BP (14% versus 11%) had a body mass index (BMI) ≥ 25.0 kg/m2. Also resting heart rate was higher in individuals with high BP (82 versus 77 beats/min). Although individuals identified with occasionally elevated BP values need further confirmatory measurements to establish the diagnosis of hypertension, these data suggest that high BP represents a noteworthy and preventable reason of concern within sub-Saharan Africa.

Hepatic lipase (LIPC) sequencing in individuals with extremely high and low high-density lipoprotein cholesterol levels

Common variants in the hepatic lipase (LIPC) gene have been shown to be associated with plasma lipid levels; however, the distribution and functional features of rare and regulatory LIPC variants contributing to the extreme lipid phenotypes are not well known. This study was aimed to catalogue LIPC variants by resequencing the entire LIPC gene in 95 non-Hispanic Whites (NHWs) and 95 African blacks (ABs) with extreme HDL-C levels followed by in silico functional analyses. A total of 412 variants, including 43 novel variants were identified; 56 were unique to NHWs and 234 were unique to ABs. Seventy-eight variants in NHWs and 89 variants in ABs were present either in high HDL-C group or low HDL-C group. Two non-synonymous variants (p.S289F, p.T405M), found in NHWs with high HDL-C group were predicted to have damaging effect on LIPC protein by SIFT, MT2 and PP2. We also found several non-coding variants that possibly reside in the circRNA and lncRNA binding sites and may have regulatory potential, as identified in rSNPbase and RegulomeDB databases. Our results shed light on the regulatory nature of rare and non-coding LIPC variants as well as suggest their important contributions in affecting the extreme HDL-C phenotypes.

Hypertension and selected indicators of health assessment in a population of 19-year-old men subject to military qualifications

Assessment the prevalence of hypertension and its relation to selected indicators of health status and performance, including classification of BMI, obesity classifications, and body structure in a large test group of 19-year-old men.The study was observational-retrospective, and included a group of 17,282 men, aged 19, from the Małopolska region. All subjects met the qualifications for compulsory military service in 2017. We analyzed selected data obtained from the records of the Ministry of National Defense-spiral-ZINT. Data collection and analysis were carried out from April 1, 2018 to August 31, 2018.Hypertension was found at 0.6%, weak body structure at 0.8% and obesityco-existing with cardiorespiratory insufficiency has been reported 2.6% of respondents and it was more frequent in the recruiters from HT II than I. The underweight concerned almost 7%, and the overweight and obesity of 1/4 of conscripts. The vast majority of people with hypertension were characterized by excessive body weight (74.8%), mainly overweight.Hypertension was seen in a negligible percentage of males studied and was significantly associated with an increase in BMI, particularly with regards to being overweight.

Apolipoprotein E-C1-C4-C2 gene cluster region and inter-individual variation in plasma lipoprotein levels: a comprehensive genetic association study in two ethnic groups

The apolipoprotein E-C1-C4-C2 gene cluster at 19q13.32 encodes four amphipathic apolipoproteins. The influence of APOE common polymorphisms on plasma lipid/lipoprotein profile, especially on LDL-related traits, is well recognized; however, little is known about the role of other genes/variants in this gene cluster. In this study, we evaluated the role of common and uncommon/rare genetic variation in this gene region on inter-individual variation in plasma lipoprotein levels in non-Hispanic Whites (NHWs) and African blacks (ABs). In the variant discovery step, the APOE, APOC1, APOC4, APOC2 genes were sequenced along with their flanking and hepatic control regions (HCR1 and HCR2) in 190 subjects with extreme HDL-C/TG levels. The next step involved the genotyping of 623 NHWs and 788 ABs for the identified uncommon/rare variants and common tagSNPs along with additional relevant SNPs selected from public resources, followed by association analyses with lipid traits. A total of 230 sequence variants, including 15 indels were identified, of which 65 were novel. A total of 70 QC-passed variants in NHWs and 108 QC-passed variants in ABs were included in the final association analyses. Single-site association analysis of SNPs with MAF>1% revealed 20 variants in NHWs and 24 variants in ABs showing evidence of association with at least one lipid trait, including several variants exhibiting independent associations from the established APOE polymorphism even after multiple-testing correction. Overall, our study has confirmed known associations and also identified novel associations in this genomic region with various lipid traits. Our data also support the contribution of both common and uncommon/rare variation in this gene region in affecting plasma lipid profile in the general population.

High prevalence of hypertension in an agricultural village in Madagascar

Elevated blood pressure presents a global health threat, with rates of hypertension increasing in low and middle-income countries. Lifestyle changes may be an important driver of these increases in blood pressure. Hypertension is particularly prevalent in African countries, though the majority of studies have focused on mainland Africa. We collected demographic and health data from 513 adults living in a community in rural Madagascar. We used generalized linear mixed models to assess body mass index (BMI), age, sex, and attributes related to household composition and lifestyle as predictors of blood pressure and hypertension. The prevalence of hypertension in this cohort was 49.1% (both sexes combined: N = 513; females: 50.3%, N = 290; males: 47.5%, N = 223). Blood pressure, as well as hypertensive state, was positively associated with age and BMI. Lifestyle and household factors had no significant relationships with blood pressure. The prevalence of hypertension was similar to that found in urban centers of other African countries, yet almost double what has been previously found in Madagascar. Future research should investigate the drivers of hypertension in rural communities worldwide, as well as the lifestyle, cultural, and genetic factors that underlie variation in hypertension across space and time.

Not a ‘Straitjacket Affair’: Anthropometrically Derived Obesity Index Correlates of Elevated Blood Pressure among University Undergraduates

Obesity is known to correlate with measures of blood pressure (BP). The nature of the correlations has, however, remained a subject of scientific enquiry, especially when BP phenotypes are disaggregated and obesity is determined by a variety of methods. This study examined the relationship between obesity and BP in young-adult Nigerians. A total of 1610 subjects (53.9% females) were recruited from five universities in the Igbo-speaking part of Nigeria. Relevant BP and anthropometric data were obtained following standard protocols. Appropriate statistical tools were used for data analyses. The results show that 42.2% (49.5% males, 36.1% females) and 13.3% (15.2% males, 11.6% females) of the population had point prehypertension and hypertension, respectively. By body mass index (BMI) standards, 20.6% (12.4% males, 27.5% females) of the population were overweight/obese. Despite the weak positive and significant correlations between BP and the measures of obesity in both males and females in the general population (r = +0.110 to +0.261; p < 0.05), the correlations were found to exist essentially in normotensives, taper in the prehypertensives, and disappear (or became negative) among hypertensives. When analysed along weight status lines, a discordant relationship was found between the sexes. Overall, the relationship between blood pressure and measures of obesity is not linear throughout the BP spectrum. Clearly the said relationship is not a ‘straitjacket affair’.

Determinants of Mean Blood Pressure and Hypertension among Workers in West Africa

Background. This review was undertaken to estimate the mean blood pressure and evaluate its determinants as well as the determinants of hypertension among workers in West Africa. Methods. In a follow-up to an earlier study, a systematic search for articles published between 1980 and August 2015 was undertaken using major databases. Results. A total of 55 articles involving 34,919 different cadres of workers from six countries were retrieved. The mean systolic blood pressure (BP) ranged from 116.6 ± 1.3 mmHg to 151.7 ± 13.6 mmHg while the mean diastolic BP ranged from 69.6 ± 11.0 mmHg to 97.1 ± 9.1 mmHg. Population-wide prehypertension was common. The major determinants of mean BP and hypertension were similar and included male sex, older age group, higher socioeconomic status, obesity, alcohol consumption, plasma glucose, and sodium excretion. Ethnicity and educational level were inconsistently associated with hypertension. Workers at higher risk of cardiovascular event did not perceive themselves as such. Conclusion. The prevailing mean prehypertensive BP, low perception of risk, and clustering of risk factors call for interventions such as healthy diets, improved physical activity, and a favourable work environment. Successful models for improving the cardiovascular health of sedentary informal sector workers in Africa are urgently needed.

Resequencing of the CETP gene in American whites and African blacks: Association of rare and common variants with HDL-cholesterol levels

BACKGROUND

Cholesteryl ester transfer protein (CETP) plays a crucial role in lipid metabolism. Associations of common CETP variants with variation in plasma lipid levels, and/or CETP mass/activity have been extensively studied and well-documented; however, the effects of uncommon/rare CETP variants on plasma lipid profile remain undefined. Hence, resequencing of the gene in extreme phenotypes and follow-up rare-variant association analyses are essential to fill this gap.

OBJECTIVE

To identify common and uncommon/rare variants in the CETP gene by resequencing the entire gene and test the effects of both common and uncommon/rare CETP variants on plasma lipid traits in two genetically distinct populations.

METHODS AND RESULTS

The entire CETP gene plus flanking regions were resequenced in 190 individuals comprising 95 non-Hispanic whites (NHWs) and 95 African blacks with extreme HDL-C levels. A total of 279 sequence variants were identified, of which 25 were novel. Selected variants were genotyped in the entire samples of 623 NHWs and 788 African blacks and 184 QC-passed variants were tested in relation to plasma lipid traits by using gene-based, single-site, haplotype and rare variant association analyses (SKAT-O). Two novel and independent associations of rs1968905 and rs289740 with HDL-C were identified in African blacks. Using SKAT-O analysis, we also identified rare variants with minor allele frequency <0.01 to be associated with HDL-C in both NHWs (P=0.024) and African blacks (P=0.009).

CONCLUSIONS

Our results point out that in addition to the common CETP variants, rare genetic variants in the CETP gene also contribute to the phenotypic variation of HDL-C in the general population.

Trends in Adolescents Obesity and the Association between BMI and Blood Pressure: A Cross-Sectional Study in 714,922 Healthy Teenagers

BACKGROUND

Seventeen percent of youth in the United States are obese. Obesity has been linked to higher prevalence of hypertension. Past studies were limited by their size and conflicting results. The aim of this study was to analyze trends in adolescents' obesity between 1998 and 2011 and to evaluate the relationship between blood pressure and body mass index (BMI) in healthy adolescents.

METHODS

All adolescents who underwent a medical exam in the years 1998-2011 and were found fit for combat duties in the Israeli Defense Force were included.

RESULTS

The cohort included 714,922 healthy adolescents with 59% of them being males. The mean age was 17.4±0.45 and mean BMI was 22±3.5 kg/m(2). The percentage of overweight adolescents (BMI > 25 kg/m(2)) has increased from 13.2% in 1998 to 21% in 2011, P < 0.001. The mean systolic and diastolic blood pressures increased with increasing BMI deciles (systolic blood pressure by 10mm Hg and diastolic blood pressure by 3-4mm Hg from the 1st decile to the 10th decile, P < 0.001 for both). In multivariate analysis, each increase of 1 unit of BMI was associated with an increased risk of systolic blood pressure above 130 mm Hg in both males (OR = 1.108, 95% CI 1.107-1.110, P < 0.001) and females (OR = 1.114, 95% CI 1.139-1.146, P < 0.001).

CONCLUSIONS

BMI in adolescents is significantly associated with systolic blood pressure and diastolic blood pressure in both genders and in both the normal weight and overweight groups. There has been consistent trend of increasing BMI values over recent years.

The prevalence, awareness, and control of hypertension among workers in West Africa: a systematic review

BACKGROUND

: Interventions in workplace settings are considered to be cost-effective in preventing cardiovascular diseases. A systematic review was conducted to assess the prevalence of hypertension and the level of awareness and control among workers in West Africa.

DESIGN

A systematic search for studies on formal and informal sector workers aged ≥15 years in West Africa published between 1980 and September 2014 was undertaken using the Ovid Medline, Embase, PubMed, and Google Scholar databases. Clinical and obstetric studies and studies that did not report prevalence were excluded. Data on study settings, characteristics of workers, blood pressure (BP) levels, prevalence of hypertension, and associated demographic factors were extracted.

RESULTS

A total of 45 studies from six countries were identified involving 30,727 formal and informal sector workers. In 40 studies with a common definition of hypertension, the prevalence ranged from 12.0% among automobile garage workers to 68.9% among traditional chiefs. In 15 of these studies, the prevalence exceeded 30%. Typically sedentary workers such as traders, bank workers, civil servants, and chiefs were at high risk. Among health care workers, the prevalence ranged from 17.5 to 37.5%. The prevalence increased with age and was higher among males and workers with higher socio-economic status. Complications of hypertension, co-morbidities, and clustering of risk factors were common. The crude prevalence of hypertension increased progressively from 12.9% in studies published in the 1980s to 34.4% in those published in 2010-2014. The proportion of hypertensives who were previously aware of their diagnosis, were on treatment or had their BP controlled was 19.6-84.0%, 0-79.2%, and 0-12.7%, respectively. Hypertensive subjects, including health workers, rarely checked their BP except when they were ill.

CONCLUSIONS

There is a high prevalence of hypertension among West Africa's workforce, of which a significant proportion is undiagnosed, severe or complicated. The clustering of risk factors, co-morbidities, and general low awareness warrant an integrated and multisectoral approach. Models for workplace health programmes aiming to improve cardiovascular health should be extended to informal sector workers.

Comprehensive evaluation of the association of APOE genetic variation with plasma lipoprotein traits in U.S. whites and African blacks

Although common APOE genetic variation has a major influence on plasma LDL-cholesterol, its role in affecting HDL-cholesterol and triglycerides is not well established. Recent genome-wide association studies suggest that APOE also affects plasma variation in HDL-cholesterol and triglycerides. It is thus important to resequence the APOE gene to identify both common and uncommon variants that affect plasma lipid profile. Here, we have sequenced the APOE gene in 190 subjects with extreme HDL-cholesterol levels selected from two well-defined epidemiological samples of U.S. non-Hispanic Whites (NHWs) and African Blacks followed by genotyping of identified variants in the entire datasets (623 NHWs, 788 African Blacks) and association analyses with major lipid traits. We identified a total of 40 sequence variants, of which 10 are novel. A total of 32 variants, including common tagSNPs (≥5% frequency) and all uncommon variants (<5% frequency) were successfully genotyped and considered for genotype-phenotype associations. Other than the established associations of APOE*2 and APOE*4 with LDL-cholesterol, we have identified additional independent associations with LDL-cholesterol. We have also identified multiple associations of uncommon and common APOE variants with HDL-cholesterol and triglycerides. Our comprehensive sequencing and genotype-phenotype analyses indicate that APOE genetic variation impacts HDL-cholesterol and triglycerides in addition to affecting LDL-cholesterol.

A multiethnic replication study of plasma lipoprotein levels-associated SNPs identified in recent GWAS

Genome-wide association studies (GWAS) have identified a number of loci/SNPs associated with plasma total cholesterol (TC), low-density lipoprotein cholesterol (LDL-C), high-density lipoprotein cholesterol (HDL-C), and triglyceride (TG) levels. The purpose of this study was to replicate 40 recent GWAS-identified HDL-C-related new loci in 3 epidemiological samples comprising U.S. non-Hispanic Whites (NHWs), U.S. Hispanics, and African Blacks. In each sample, the association analyses were performed with all 4 major lipid traits regardless of previously reported specific associations with selected SNPs. A total of 22 SNPs showed nominally significant association (p<0.05) with at least one lipid trait in at least one ethnic group, although not always with the same lipid traits reported as genome-wide significant in the original GWAS. The total number of significant loci was 10 for TC, 12 for LDL-C, 10 for HDL-C, and 6 for TG levels. Ten SNPs were significantly associated with more than one lipid trait in at least one ethnic group. Six SNPs were significantly associated with at least one lipid trait in more than one ethnic group, although not always with the same trait across various ethnic groups. For 25 SNPs, the associations were replicated with the same genome-wide significant lipid traits in the same direction in at least one ethnic group; at nominal significance for 13 SNPs and with a trend for association for 12 SNPs. However, the associations were not consistently present in all ethnic groups. This observation was consistent with mixed results obtained in other studies that also examined various ethnic groups.

The confounding effect of cryptic relatedness for environmental risks of systolic blood pressure on cohort studies

The impact of cryptic relatedness (CR) on genomic association studies is well studied and known to inflate false-positive rates as reported by several groups. In contrast, conventional epidemiological studies for environmental risks, the confounding effect of CR is still uninvestigated. In this study, we investigated the confounding effect of unadjusted CR among a rural cohort in the relationship between environmental risk factors (body mass index, smoking status, alcohol consumption) and systolic blood pressure. We applied the methods of population-based whole-genome association studies for the analysis of the genome-wide single nucleotide polymorphism data in 1622 subjects, and detected 20.2% CR in this cohort population. In the case of the sample size, approximately 1000, the ratio of CR to the population was 20.2%, the population prevalence 25%, the prevalence in the CR 26%, heritability for liability 14.3% and prevalence in the subpopulation without CR 26%, the difference of estimated regression coefficient between samples with and without CR was not significant (P-value = 0.55). On the other hand, in another case with approximately >20% heritability for liability, we showed that confounding due to CR biased the estimation of exposure effects.

Oral contraceptive use in girls and alcohol consumption in boys are associated with increased blood pressure in late adolescence

AIMS

Lifestyle behaviours established during adolescence may adversely affect blood pressure (BP) and contribute to gender differences in cardiovascular risk in adulthood. We aimed to assess the association of health behaviours with BP in adolescents, using data from the Western Australian Pregnancy (Raine) Study.

METHODS

Cross-sectional analysis on 1248 Raine Study adolescents aged 17 years, to examine associations between lifestyle factors and BP.

RESULTS

Boys had 8.97 mmHg higher systolic BP, as compared with girls. The 30% of girls using oral contraceptives (OC) had 3.27 and 1.74 mmHg higher systolic and diastolic BP, respectively, compared with non-users. Alcohol consumption in boys, increasing body mass index (BMI) and the sodium-potassium ratio were associated with systolic BP. We found a continuous relationship between BMI and systolic BP in both genders; however, the gradient of this relationship was significantly steeper in boys, compared with girls not taking OC. In boys, systolic BP was 5.7 mmHg greater in alcohol consumers who were in the upper quartile of BMI and the urinary sodium-potassium ratio compared with teetotallers in the lowest quartile. In girls, systolic BP was 5.5 mmHg higher in those taking OC, in the highest BMI and urinary sodium-potassium ratio quartile as compared to those not taking the OC pill and in the lowest quartile.

CONCLUSION

In addition to gender-related differences in the effects of adiposity on BP, we found lifestyle-related health behaviours such as high salt intake for both sexes, consumption of alcohol in boys, and OC use in girls were important factors associated with BP measurements in late adolescence. This suggests that gender-specific behavioural modification in adolescence may prevent adult hypertension.

Obesity and blood pressure levels of adolescents in Abeokuta, Nigeria

BACKGROUND

We determined the prevalence of general and central obesity and their relationship with blood pressure levels among adolescents in Abeokuta, Nigeria.

METHODS

We selected 423 adolescents from seven schools in Abeokuta, Nigeria, using a multistage random-sampling technique. Body mass index (BMI), waist circumference (WC) and blood pressures were measured.

RESULTS

Twenty-one (5%) children had general obesity and 109 (24.5%) had central obesity. Of those with general obesity, 20 (95.1%) children were centrally obese. With simple linear regression analysis, BMI and WC explained 10.7 and 8.4%, respectively of the variance in systolic blood pressure (SBP), and 3.6 and 2.7%, respectively of the variance in diastolic blood pressure (DBP). Following logistic regression analysis, BMI was the major factor determining SBP levels (OR 0.8, 95% CI: 0.65-0.99, p < 0.05).

CONCLUSION

BMI remains an important anthropometric screening tool for high blood pressure in Nigerian adolescents.

Body size and blood pressure: an analysis of Africans and the African diaspora

BACKGROUND

Blood pressure is directly and causally associated with body mass index (BMI) in populations worldwide. However, the relationship may vary across BMI in populations of African origin.

METHODS

We compared the relationship between blood pressure and BMI in populations of African origin, using 13 samples from Africa, the Caribbean, the United Kingdom and the United States. We had access to data from individual participants for age, height, weight, blood pressure, and treatment of hypertension. Analysis was restricted to 18,072 participants (age 35-64 years; 44% men). We carried out multivariate regression analysis to estimate the relationship between blood pressure and BMI by country and by sex. The use of antihypertensive treatment was taken into account by exclusion and by sensitivity analysis.

RESULTS

There was a positive relationship between both systolic and diastolic blood pressure and BMI. In men the slopes for systolic blood pressure varied from 0.27 mm Hg per kg/m (95% confidence interval = -0.01 to 0.56) in the United States to 1.72 mm Hg per kg/m (95% confidence interval = 0.92 to 2.53) in Ghana (Kumasi). In women, the slopes varied from 0.08 (-0.54 to 0.72) in South Africa to 1.32 (0.98 to 1.66) in the Republic of Congo. Similar variation in trends was seen for diastolic blood pressure. The higher the BMI, the shallower the slopes [-0.10 (-0.15 to -0.06) for systolic, -0.09 (-0.12 to -0.06) for diastolic]. No differences were seen after excluding persons who were being treated for hypertension.

CONCLUSIONS

Blood pressure and BMI levels vary among populations of the African diaspora. The effect of BMI on blood pressure levels diminishes as BMI increases. These results suggest a complex relationship among excess body weight, adiposity, and energy expenditure.

A cross-sectional study of vascular risk factors in a rural South African population: data from the Southern African Stroke Prevention Initiative (SASPI)

BACKGROUND

Rural sub-Saharan Africa is at an early stage of economic and health transition. It is predicted that the 21st century will see a serious added economic burden from non-communicable disease including vascular disease in low-income countries as they progress through the transition. The stage of vascular disease in a population is thought to result from the prevalence of vascular risk factors. Already hypertension and stroke are common in adults in sub-Saharan Africa. Using a multidisciplinary approach we aimed to assess the prevalence of several vascular risk factors in Agincourt, a rural demographic surveillance site in South Africa.

METHODS

We performed a cross sectional random sample survey of adults aged over 35 in Agincourt (population approximately 70 000). Participants were visited at home by a trained nurse who administered a questionnaire, carried out clinical measurements and took a blood sample. From this we assessed participants' history of vascular risk, blood pressure using an OMRON 705 CP monitor, waist circumference, body mass index (BMI), ankle brachial index (ABI), and total and HDL cholesterol.

RESULTS

402 people (24% men) participated. There was a high prevalence of smoking in men, but the number of cigarettes smoked was small. There was a striking difference in mean BMI between men and women (22.8 kg/m2 versus 27.2 kg/m2), but levels of blood pressure were very similar. 43% of participants had a blood pressure greater than 140/90 or were on anti-hypertensive treatment and 37% of participants identified with measured high blood pressure were on pharmacological treatment. 12% of participants had an ABI of < 0.9, sugesting the presence of sub-clinical atheroma. 25.6% of participants had a total cholesterol level > 5 mmol/l.

CONCLUSION

We found a high prevalence of hypertension, obesity in women, and a suggestion of subclinical atheroma despite relatively favourable cholesterol levels in a rural South African population. South Africa is facing the challenge of an emerging epidemic of vascular disease. Research to establish the social determinates of these risk factors and interventions to reduce both individual and population risk are required.

Physiology, Genetics, and Cardiovascular Disease: Focus on African Americans

The disproportionate impact of cardiovascular disease in African Americans is well recognized. Not only do risk factors such as obesity occur at a higher rate in the African-American community, but this population experiences a greater mortality from cardiovascular disease than their white counterparts. The cardiovascular system is regulated in part by two opposing mediators linking the risk factors of obesity, vascular dysfunction, and diabetes. One of these mediators--angiotensin II--increases blood pressure, impairs endothelial function, decreases peroxisome proliferator activated-receptor gamma, and is proinflammatory, growth stimulating, profibrotic, and proatherogenic. The other mediator, peroxisome proliferator activated-receptor gamma, lowers blood pressure, improves endothelial function, decreases angiotensin II type 1 receptor function, and is anti-inflammatory, growth-inhibiting, antifibrotic, and antiatherogenic. Genotypic variants have been discovered that affect the functioning of both of these important systems. Some of these variants--like some genotypic variants discovered in the adrenergic system--occur with different frequencies in African Americans than in Americans of European descent and may help to explain racial/ethnic differences in susceptibility to cardiovascular disease and aspects of the response to treatment. Recognition of these genotypic differences may permit the development of therapies tailored to individual patients.

Association between body mass index and blood pressure across three populations in Africa and Asia

Despite a growing burden of obesity and hypertension in developing countries, there is limited information on the contribution of body mass index (BMI) to blood pressure (BP) in these populations. This study examines the association between BMI and BP in three populations across Africa and Asia. Data on BMI, BP and other background characteristics of study participants were generated using the World Health Organization STEPwise approach to surveillance (STEPS), at three demographic surveillance sites in Ethiopia, Vietnam and Indonesia. BMI and BP increased along the socioeconomic gradient across the three countries. Mean (s.d.) BMI in men varied between 19.41 (2.28) in Ethiopia to 21.17 (2.86) in Indonesia. A high prevalence of overweight/obesity was noted among Indonesian women (25%) and men (10%), whereas low BMI was widely prevalent in Ethiopia and Vietnam, ranging from 33 to 43%. Mean (s.d.) systolic BP (SBP) among men varied between 117.15 (15.35) in Ethiopia to 127.33 (17.80) in Indonesia. The prevalence of hypertension was highest among women (25%) and men (24%) in Indonesia. Mean BP levels increased with increasing BMI. The risk of hypertension was higher among population groups with overweight and obesity (BMI>/=25 kg/m(2)); odds ratio (95% confidence interval); 2.47 (1.42, 4.29) in Ethiopia, 2.67 (1.75, 4.08) in Vietnam and 7.64 (3.88, 15.0) in Indonesia. BMI was significantly and positively correlated with both SBP and DBP in all the three populations, correlation coefficient (r) ranging between 0.23 and 0.27, P<0.01. High BP exists in a background of undernutrition in populations at early stages of the epidemiologic transition.

Blood pressure and body mass index in lean rural and semi-urban subjects in West Africa

BACKGROUND

Blood pressure (BP) is positively related to body mass index (BMI) in persons of both Caucasian and African origin, but the precise nature of the relationship is unclear.

OBJECTIVE

To study the relationship between BP and BMI in a lean African population.

DESIGN

A community-based cross-sectional study.

METHODS

The BMI and BP were measured in 362 men and 592 women aged 40-75 years living in Ashanti, Ghana. In total, 498 lived in semi-urban areas and 456 in rural villages.

RESULTS

The BMI was higher among semi-urban women [23.1 kg/m (95% confidence interval (CI), 22.5 to 23.6)] than semi-urban men [20.9 kg/m (95% CI, 20.6 to 21.5)], rural men [19.5 kg/m (95% CI, 19.1 to 19.9)] and rural women [19.9 kg/m (95% CI, 19.5 to 20.3)]. For systolic BP in women older than 52 years and in semi-urban women, the relationship was non-linear. The slope of the line below the change point ("knot") was greater than that above it. There was no evidence of non-linearity in men. For diastolic BP only younger women had a significant "knot" point at 18 kg/m. Again, the slope of the line below the "knot" was greater than that above it. In men, however, there was also evidence of a "knot" in younger and rural men, with the slope of the line below the "knot" being less that that above it (unlike in women).

CONCLUSIONS

The relationship between BP and BMI is not linear, and is possibly sigmoid, but this may vary between subgroups.

Using generalized additive models to reduce residual confounding

Traditionally, confounding by continuous variables is controlled by including a linear or categorical term in a regression model. Residual confounding occurs when the effect of the confounder on the outcome is mis-modelled. A continuous representation of a covariate was previously shown to result in a less biased estimate of the adjusted exposure effect than categorization provided the functional form of the covariate-outcome relationship is correctly specified. However, this is rarely known. In contrast to parametric regression, generalized additive models (GAM) fit a smooth dose-response curve to the data, without requiring a priori knowledge of the functional form. We used simulations to compare parametric multiple logistic regression vs its non-parametric GAM extension in their ability to control for a continuous confounder. We also investigated several issues related to the implementation of GAM in this context, including: (i) selecting the degrees of freedom; and (ii) alternative criteria for inclusion/exclusion of the potential confounder and for choosing between parametric and non-parametric representation of its effect. The impact of the shape and strength of the confounder-disease association, sample size, and the correlation between the confounder and exposure were investigated. Simulations showed that when the confounder has a non-linear association with the outcome, compared to a parametric representation, GAM modelling (i) reduced the mean squared error for the adjusted exposure effect; (ii) avoided inflation of the type I error for testing the exposure effect. When the true confounder-outcome relationship was linear, GAM performed as well as the parametric logistic regression. When modelling a continuous exposure non-parametrically, in the presence of a continuous confounder, our results suggest that assuming a linear effect of the confounder and focussing on the non-linearity of the exposure-outcome relationship leads to spurious findings of non-linearity: joint non-linear modelling is necessary. Overall, our results suggest that the use of GAM to reduce residual confounding offers several improvements over conventional parametric modelling.

Insulin resistance and the sympathetic nervous system

The obesity epidemic is driving metabolic (insulin resistance) syndrome-related health problems including an approximately threefold increased coronary heart disease risk. Sympathetic hyperfunction may participate in the pathogenesis and complications of the metabolic syndrome including higher blood pressure, a more active renin-angiotensin system, insulin resistance, faster heart rates, and excess cardiovascular disease including sudden death. Possible factors augmenting sympathetic activation in the metabolic syndrome include alterations of insulin, leptin, nonesterified fatty acids (NEFAs), cytokines, tri-iodothyronine, eicosanoids, sleep apnea, nitric oxide, endorphins, and neuropeptide Y. Of note, high plasma NEFAs are a risk factor for hypertension and sudden death. In short-term human studies, NEFAs can raise blood pressure, heart rate, and a(1)-adrenoceptor vasoreactivity, while reducing baroreflex sensitivity, endothelium-dependent vasodilatation, and vascular compliance. Efforts to further identify the mechanisms and consequences of sympathetic dysfunction in the metabolic syndrome may provide insights for therapeutic advances to ameliorate the excess cardiovascular risk and adverse outcomes.

Cladistic analysis of human apolipoprotein a4 polymorphisms in relation to quantitative plasma lipid risk factors of coronary heart disease

Genetic variation in several genes involved in lipid metabolism is known to affect population variation in quantitative lipid risk factor profiles for coronary heart disease (CHD). The apolipoprotein A-IV gene (APOA4) is one such candidate gene. We genotyped five polymorphisms in the APOA4 gene (codon 127, codon 130, codon347, codon 360 and 3' VNTR) and investigated their impact on plasma lipid trait levels in three populations comprising 604 U.S. non-Hispanic Whites (NHWs), 408 U.S. Hispanics and 708 Nigerian Blacks. Cladistic analysis was carried out to identify 5-site haplotypes that were associated with significant phenotypic differences in each population. The distribution of APOA4 genotypes was significantly different between ethnic groups. The Africans were monomorphic for two of the five sites (codons 130 and 360), but possess a unique 12 bp insertion that was not observed in NHWs and Hispanics. Due to linkage disequilibrium between the sites, only 6 haplotypes were observed in NHWs and Hispanics, and 4 in Africans. Several gender-and ethnic-specific associations between genotypes and plasma lipid traits were observed when single sites were used. Several haplotypes were identified by cladistic analysis that may carry functional mutations that affect plasma lipid trait levels.

Physical activity and its relationship with obesity, hypertension and diabetes in urban and rural Cameroon

OBJECTIVES

To evaluate and compare physical activity patterns of urban and rural dwellers in Cameroon, and study their relationship with obesity, diabetes and hypertension.

METHODS

We studied 2465 subjects aged >or=15 y, recruited on the basis of a random sampling of households, of whom 1183 were urban dwellers from Yaoundé, the capital city of Cameroon and 1282 rural subjects from Bafut, a village of western Cameroon. They all had an interviewer-administered questionnaire for the assessment of their physical activity and anthropometric measurements, blood pressure and fasting blood glucose determination. The procedure was satisfactorily completed in 2325 (94.3%) subjects. Prevalences were age-adjusted and subjects compared according to their region, sex and age group.

RESULTS

Obesity was diagnosed in 17.1 and 3.0% urban and rural women, respectively (P<0.001), and in 5.4 vs 1.2% urban and rural men, respectively (P<0.001). The prevalence of hypertension was significantly higher in urban vs rural dwellers (11.4 vs 6.6% and 17.6 vs 9.1% in women and men, respectively; P<0.001). Diabetes was more prevalent in urban compared to rural women (P<0.05), but not men. Urban subjects were characterized by lower physical activity (P<0.001), light occupation, high prevalence of multiple occupations, and reduced walking and cycling time compared to rural subjects. Univariate analysis showed significant associations between both physical inactivity and obesity and high blood pressure. The relationship of physical inactivity with hypertension and obesity were independent in both urban and rural men, but not in women. Body mass index, blood pressure and glycaemia were higher in the first compared with the fourth quartiles of energy expenditure.

CONCLUSION

Obesity, diabetes and hypertension prevalence is higher in urban compared to rural dwellers in the populations studied. Physical activity is significantly lower and differs in pattern in urban subjects compared to rural. Physical inactivity is associated with these diseases, although not always significant in women.

Physical activity and cardiovascular risk factors in a developing population

PURPOSE

Noncommunicable diseases are emerging in developing countries. However, few studies have been conducted in those countries to evaluate the role of physical activity in the development of cardiovascular diseases. This study investigated physical activity and its relationship to risk factors for cardiovascular disease in a large population (N = 799) of civil servants from Benin City, Nigeria.

METHODS

Physical activity levels were estimated by an interviewer-administered questionnaire, which determined the average hours per week over the past year spent in occupational and leisure activities. Time spent walking or biking to work was assessed as well. Other major measures included body mass index (BMI), waist-hip ratio (WHR), blood pressures, plasma insulin level, lipid profiles, and diet.

RESULTS

More of the physical activity was attributed to occupational than to leisure activities. Compared with women, men had a higher activity level. No significant trend was observed across age groups. Male senior staff (a marker of higher socioeconomic status) had a lower physical activity level than male junior staff. Physical activity, especially time walking or biking to work, was inversely correlated with weight, BMI, WHR, blood pressures, insulin, total cholesterol, LDL and HDL cholesterol, and triglycerides in men, while such correlations were not consistent in women. In multivariate analysis in men, blood pressure and insulin were independently associated with BMI but not with walking, while an independent inverse association was seen between walking and BMI.

CONCLUSION

Lack of physical activity was associated with adverse risk profiles for cardiovascular disease in this developing population.

Gender-specific nonrandom association between the alpha 1-antichymotrypsin and apolipoprotein E polymorphisms in the general population and its implication for the risk of Alzheimer's disease

A common polymorphism in the alpha 1-antichymotrypsin (ACT) gene has been found co modify the APOE*4-associated risk of Alzheimer's disease due to an apparent interaction between the two loci. This study was undertaken to determine the gender- and age-related distributions of these two polymorphisms in two large population-based samples of Caucasians (n = 803) and Nigerian Blacks (n = 730). Significantly higher frequencies of the ACT*A (78.6% vs. 48.4%; P < 0.001) and APOE*4 (25.6% vs. 15.6%; P < 0.001) alleles were observed in Nigerian Blacks than in Caucasians. In Caucasian women but not in men, the frequency of the APOE*4 allele was significantly lower in the ACT/AA genotype as compared to the ACT/AT and ACT/TT genotypes, while a reverse trend was seen for the APOE*3 allele frequency among the ACT genotypes. The distribution of the ACT*A allele between the APOE*4 carriers and non-APOE*4 carriers was also different in Caucasian women but not in men. A similar gender-specific nonrandom association between the two polymorphisms was observed in Black women but this was not as strong as observed in Caucasian women. When the two samples were stratified by age group, an association or trend of association was observed in all age groups in women only. These data indicate the existence of a nonrandom association between the APOE and ACT loci in women which may have an important implication for the higher prevalence of Alzheimer's disease in women.

Insulin and hypertension in the NHLBI Family Heart Study: a sibpair approach to a controversial issue

The association between insulin and hypertension remains equivocal. We therefore investigated insulin levels in 3037 normotensive and 1067 hypertensive subjects from the National Heart, Lung and Blood Institute (NHLBI) Family Heart Study (FHS) by two different approaches. First, we compared insulin levels between normotensive and 275 untreated hypertensive subjects. Insulin levels unadjusted as well as adjusted for age, sex, and center were significantly higher in hypertensives. After adjustment for body mass index (BMI), insulin remained significantly higher only in the diastolic hypertensive group (mean +/- SD 77.0 +/-36.7 pmol/L, P < .01) but not in the isolated systolic hypertensive group (67.0 +/- 38.2 pmol/L) when compared to normotensives (63.2 +/- 29.1 pmol/L). A sibpair analysis was then used that compared the intra-sibpair differences in insulin concentrations to the intra-sibpair differences in blood pressure (BP) levels. This approach was intended to control for the effects of genetic and residual shared environmental variance upon insulin levels. The intra-sibpair difference in insulin concentrations between concordant (diastolic and systolic deltaBP < 5 mm Hg) and discordant sibpairs (diastolic and systolic deltaBP > 15 and > 20 mm Hg, respectively) was no longer significantly different when adjusted for BMI (2.7 v 5.9 pmol/L for diastolic and -1.7 v -1.8 pmol/L for systolic BP). Even the random selection of one sibpair from each of the 326 families independently of insulin and BP levels did not result in a significant correlation between the intrasibpair differences in insulin and BP. Using an insulin resistance index instead of insulin did not change our findings. Our investigation in the FHS sample of families suggests that there is only a small, if any, influence of insulin levels on BP after adjustment for obesity-related sources of variation.

Electrocardiographic left ventricular hypertrophy by five criteria among civil servants in Benin City, Nigeria: prevalence and correlates

Although increasing hypertension rates have been reported in several African populations, little is known about the frequency of resulting hypertensive complications in these populations. We recorded the electrocardiograms of 482 male and 284 female civil servants in Benin City, Nigeria. Five different criteria were used to detect the presence of electrocardiographic left ventricular hypertrophy. Associations between electrocardiographic left ventricular hypertrophy and demographic, anthropometric and blood pressure characteristics were assessed. The prevalence of electrocardiographic left ventricular hypertrophy ranged from 3 to 29% in the total population, depending on the criteria used, with four of the five criteria resulting in prevalence estimates of less than 10%. The prevalence of electrocardiographic left ventricular hypertrophy was significantly greater among those with hypertension (19% of the total population), ranging from 11 to 49%. The prevalence of electrocardiographic left ventricular hypertrophy increased with blood pressure level in both normotensives and hypertensives. Among hypertensives with systolic blood pressure > or =180 mm Hg or diastolic blood pressure > or =110 mm Hg, the prevalence exceeded 50% by four of the five criteria. We conclude that left ventricular hypertrophy may be affecting many hypertensives in this Nigerian population, potentially resulting in a substantial future burden of cardiovascular disease and death.

What is the role of obesity in hypertension and target organ injury in African Americans?

Hypertension is the most common reversible risk factor for cardiovascular disease. It is especially common in African Americans. One of the factors that may contribute to the high rates of hypertension and target organ injury in African Americans is obesity. Hypertension and obesity are common among African Americans. Obesity is particularly common in African American women. About 75% of African American women are obese. Regulation of both body weight and blood pressure are complex, involving an interaction of genetic and environmental factors. Most research thus far has focused on blood pressure control systems studied in other forms of hypertension, including the sympathetic nervous system, the renin angiotensin system, and metabolic factors-primarily insulin resistance. Proposed mechanisms that are unique to obesity-associated hypertension include: 1) intrarenal physical forces associated with obesity-induced changes in the renal medulla; 2) genetic/metabolic factors; and 3) metabolic effects of abdominal visceral fat. The Jackson Heart Study provides a unique opportunity to address unresolved questions in the relationship of body weight, blood pressure, and cardiovascular disease.

Nonpharmacologic Approaches to Therapy for Hypertension

OBJECTIVE

To provide an overview of nondrug therapeutic modalities for management of hypertension.

METHODS

We review four strategies that involve lifestyle changes--weight reduction, moderation of sodium intake, physical activity, and moderation of alcohol consumption--that can potentially have a blood pressure-lowering effect.

RESULTS

Several clinical trials have shown that a weight loss of 10 to 20% will significantly decrease blood pressure. An average of 1 to 2 mm Hg reduction in blood pressure may occur per kilogram of weight lost. Although sodium restriction has less effect on blood pressure than does weight reduction, a decrease in sodium intake to <100 mmol/day can yield a mean blood pressure reduction of 3 to 5 mm Hg systolic and 2 to 3 mm Hg diastolic. Exercise regimens have demonstrated convincing antihypertensive effects. In recent randomized studies, the average reduction in blood pressure ranged from 5 to 15 mm Hg for systolic measurements and 5 to 10 mm Hg for diastolic readings. Alcohol consumption has been shown to have one of the strongest associations with blood pressure among the potentially modifiable risk factors for hypertension. An average of 1 mm Hg decrease in blood pressure has been noted per one drink/day reduction in consumption.

CONCLUSION

Lifestyle changes that can decrease blood pressure are important because they may not only eliminate the need for drug treatment but also decrease other cardiovascular risk factors.

The role of socioeconomic status and serum fatty acids in the relationship between intake of animal foods and cardiovascular risk factors

Little is known regarding the relationship of serum fatty acids to cardiovascular risk factors in Nigerian populations. Civil servants with higher socioeconomic status (SES) in Nigeria appear to be in cultural transition toward a more Westernized lifestyle. For this study the food intakes of 397 civil servants were estimated from two 24-h recalls. Fatty acids in serum total lipids were measured in both absolute weight concentration and percentage composition. Daily meat intake was 43.5 g, and fish intake was 70.5 g. The intakes of meat, eggs, and milk were higher in high SES Nigerians than in low SES Nigerians. The concentration of total fatty acids (TFA, the sum of 12 serum fatty acids) was also higher in high SES men and women, as compared with low SES men and women (2064, 2060, 1831, and 1776 mg/L, respectively). There were significant direct associations between meat intake and serum level of arachidonic acid, and between fish intake and serum levels of eicosapentaenoic acid and docosahexaenoic acid. TFA was positively associated with cholesterol, low-density-lipoprotein cholesterol (LDLc), and triglycerides across gender and SES groups after adjustment for body mass index, fasting insulin level, and age. Nigerian women were compared with two groups of American women. We concluded that fatty acids in absolute weight concentration reflected the amount of fat intake. The level of TFA was directly related to cardiovascular risk factors in Nigerians. Follow-up of such populations in cultural transition can facilitate the understanding of the true roles of animal food intake in the early evolution of atherosclerosis.

Correlates of serum lipids in a lean black population

Exposure to an urban, sedentary work environment and higher socioeconomic status (SES) may stimulate adoption of Westernized lifestyles by populations in developing countries reversing the historically low risk for coronary heart disease. In a study of serum lipids in 1407 Nigerian civil servants, aged 25-54 years, we found a more atherogenic lipid profile among higher SES males and females compared with lower SES (LDL-cholesterol, 113 vs. 97 mg/dl, males, 125 vs. 114 mg/dl, females). Mean body mass index (BMI, kg/m2) in higher and lower SES was 22.6 and 21.3, respectively, males, and 24.7 and 24.4, respectively females. A strong relationship was observed between BMI and lipids although this relationship was absent among the leanest half of the population (BMI < 21.8). In multiple regression, SES and BMI were both strong and independent predictors of cholesterol. Both high and low SES consumed a typical Nigerian low fat, high carbohydrate diet, but somewhat higher meat, milk and egg intake suggested that some Westernization of the diet had occurred among the higher SES. Physical activity was lower among the higher SES. We conclude that SES related changes in lifestyle contribute to substantially higher total and LDL-cholesterol even in a generally lean population consuming a low fat diet.