Relationship of adiposity and cardiorespiratory fitness with resting blood pressure of South African adolescents: the PAHL Study

Hypertension among adolescents in sub-Saharan Africa: a systematic review

Introduction

Hypertension (HTN) among adolescents is common in high-income countries, and leads to increased premature cardiovascular diseases (CVD). In sub-Saharan Africa (SSA), the prevalence of HTN among adolescents, associated risk factors and CVD complications are not well-described. Such data is needed for planning public health programs to prevent premature CVD in SSA.

Methods

We systematically searched 5 databases (MEDLINE, Embase, Google Scholar, Web of Science, and African Index Medicus) from their establishment to December 2021. Key search terms were: adolescent, arterial hypertension, and names of the 48 countries in SSA. We used Covidence® to manage the search results. The review was registered in the Open Science Framework (OSF) https://osf.io/p5sbt/.

Results

We identified 4,008 articles out of which we screened 3,088 abstracts, and reviewed 583 full-text articles. We finally included 92 articles that were published between 1968 to December 2021. The majority were cross-sectional studies (80%) and conducted in school settings (78%). The risk of bias was low for 59 studies (64.1%), moderate for 29 studies (31.5%), and high for 4 studies (4.3%). Overall, the prevalence of HTN varied widely from 0.18% to 34.0% with a median (IQR) of 5.5% (3.1%, 11.1%). It was relatively higher in studies using automated blood pressure (BP) devices, and in studies defining HTN using thresholds based on percentile BP distribution for one's height, age, and sex. In addition, the prevalence of HTN was significantly higher in studies from Southern Africa region of SSA and positively correlated with the year of publication. Across studies, traditional risk factors such as age, sex, body mass index, and physical inactivity, were commonly found to be associated with HTN. In contrast, non-traditional risk factors related to poverty and tropical diseases were rarely assessed. Only three studies investigated the CVD complications related to HTN in the study population.

Conclusion

The prevalence of HTN among adolescents in SSA is high indicating that this is a major health problem. Data on non-traditional risk factors and complications are scarce. Longitudinal studies are needed to clearly define the rates, causes, and complications of HTN.

Systematic Review Registration

https://osf.io/p5sbt/, identifier (10.17605/OSF.IO/P5SBT).

Elevated blood pressure among adolescents in sub-Saharan Africa: a systematic review and meta-analysis

BACKGROUND

More people from sub-Saharan Africa aged between 20 years and 60 years are affected by end-organ damage due to underlying hypertension than people in high-income countries. However, there is a paucity of data on the pattern of elevated blood pressure among adolescents aged 10-19 years in sub-Saharan Africa. We aimed to provide pooled estimates of high blood pressure prevalence and mean levels in adolescents aged 10-19 years across sub-Saharan Africa.

METHODS

In this systematic review and meta-analysis, we searched PubMed, Google Scholar, African Index Medicus, and Embase to identify studies published from Jan 1, 2010, to Dec 31, 2021. To be included, primary studies had to be observational studies of adolescents aged 10-19 years residing in sub-Saharan African countries reporting the pooled prevalence of elevated blood pressure or with enough data to compute these estimates. We excluded studies on non-systemic hypertension, in African people not living in sub-Saharan Africa, with participant selection based on the presence of hypertension, and with adult cohorts in which we could not disaggregate data for adolescents. We independently extracted relevant data from individual studies using a standard data extraction form. We used a random-effects model to estimate the pooled prevalence of elevated blood pressure and mean systolic blood pressure (SBP) and diastolic blood pressure (DBP) levels overall and on a sex-specific basis. This study is registered with PROSPERO (CRD42022297948).

FINDINGS

We identified 2559 studies, and assessed 81 full-text studies for eligibility, of which 36 studies comprising 37 926 participants aged 10-19 years from ten (20%) of 49 sub-Saharan African countries were eligible. A pooled sample of 29 696 adolescents informed meta-analyses of elevated blood pressure and 27 155 adolescents informed meta-analyses of mean blood pressure. Sex data were available from 26 818 adolescents (14 369 [53·6%] were female and 12 449 [46·4%] were male) for the prevalence of elevated blood pressure and 23 777 adolescents (12 864 [54·1%] were female and 10 913 [45·9%] were male) for mean blood pressure. Study quality was high, with no low-quality studies. The reported prevalence of elevated blood pressure ranged from 4 (0·2%) of 1727 to 1755 (25·1%) of 6980 (pooled prevalence 9·9%, 95% CI 7·3-12·5; I?=99·2%, p_{heterogeneity}<0·0001). Mean SBP was 111 mm Hg (95% CI 108-114) and mean DBP was 68 mm Hg (66-70). 13·4% (95% CI 12·9-13·9; p_{heterogeneity}<0·0001) of male participants had elevated blood pressure compared with 11·9% (11·3-12·4; p_{heterogeneity}<0·0001) of female participants (odds ratio 1·04, 95% CI 0·81-1·34; p_{heterogeneity}<0·0001).

INTERPRETATION

To our knowledge, this systematic review and meta-analysis is the first systematic synthesis of blood pressure data specifically derived from adolescents in sub-Saharan Africa. Although many low-income countries were not represented in our study, our findings suggest that approximately one in ten adolescents have elevated blood pressure across sub-Saharan Africa. Accordingly, there is an urgent need to improve preventive heart-health programmes in the region.

FUNDING

None.

A new set of estimated cardiorespiratory fitness equations are associated with cognitive performance in older adults

This study aimed to develop new equations to estimate cardiorespiratory fitness specifically for older adults and, secondly, to analyze the associations of cardiorespiratory fitness, both objectively measured and estimated using new equations, with cognitive performance. Ninety-two older adults (41 females, 65-75 years) from baseline data of a randomized controlled trial were analyzed ("ClinicalTrials.gov" Identifier: NCT03923712). Participants completed 4 measurement sessions including (i) physiological and health indicators in a laboratory setting, (ii) field-based fitness tests, (iii) sociodemographic and physical activity questionnaires, and (iv) a battery of neuropsychological tests to evaluate cognitive performance. The main findings were as follows: (i) a set of new equations with good predictive value for estimated cardiorespiratory fitness were developed (74-87%), using different scenarios of complexity and/or equipment requirements, and (ii) higher estimated cardiorespiratory fitness, even using its simplest equation (eCRF =  - 1261.99 + 1.97 × 6 min walking test (m) + 1.12 × bioimpedance basal metabolic rate (kcal/day) + 5.25 × basal heart rate (bpm)), was associated with better cognitive performance evaluated by several neuropsychological tests (i.e., language, cognitive flexibility, fluency, attention, and working memory), similar to using objectively measured cardiorespiratory fitness. In summary, a new set of estimated cardiorespiratory fitness equations have been developed with predictive values ranging from 74 to 87% that could be used based on necessity, availability of equipment, resources, or measurement context. Moreover, similar to objectively measured cardiorespiratory fitness, this measure of estimated cardiorespiratory fitness was positively associated with performance on language, fluency, cognitive flexibility, attention, and working memory, independently of sex, age, and education level.

Body fat percentage, cardiorespiratory fitness and arterial blood pressure in children and adolescents: a longitudinal analysis

Background

A better understanding of how cardiorespiratory fitness (CRF) and adiposity interact to associate with arterial blood pressure over time remains inconclusive. Thus, the aim of the present study was to examine whether changes in CRF moderates the association between body fat percentage (BF%) and arterial blood pressure in children and adolescents.

Methods

This is an observational longitudinal study with 407 children and adolescents aged 8–17 years followed-up for three years from a city in Southern Brazil. Participants were evaluated in 2011 and 2014. CRF was measured by validated field-based tests following the Projeto Esporte Brazil protocols and peak oxygen uptake (VO_2peak) was estimated. BF% was determined by the measures of tricipital and subscapular skinfolds using equations according to sex. Systolic and diastolic blood pressure (SBP, DBP) were measured with a sphygmomanometer according to standard procedures. Moderation analyses included multiple linear regression models adjusted for sex, age, pubertal status, height, socioeconomic level, skin color, and the arterial blood pressure variable itself at baseline.

Results

It was observed a significant inverse association between VO_2peak at baseline with SBP (β = − 0.646 CI95% = − 0.976  − 0.316) and DBP (β = − 0.649 CI95% = − 0.923  − 0.375) at follow-up and a positive association between BF% at baseline with SBP (β = 0.274; CI95% = 0.094 0.455) and DBP (β = 0.301; CI95% = 0.150 0.453) at follow-up. In addition, results indicated a significant interaction term between changes in VO_2peak and BF% at baseline with both SBP (p = 0.034) and DBP at follow-up (p = 0.011), indicating that an increase of at least 0.35 mL/kg/min and 1.78 mL/kg/min in VO_2peak attenuated the positive relationship between BF% with SBP and DBP.

Conclusion

CRF moderates the relationship between BF% and SBP and DBP in children and adolescents.

Anthropometric indicators of body fat as discriminators of low levels of cardiorespiratory fitness in adolescents

PURPOSE

To evaluate the discriminatory power of anthropometric indicators of body fat (BF) for identifying low levels of cardiorespiratory fitness, as well as the association between cutoff points and low levels of cardiorespiratory fitness in adolescents.

DESIGN AND METHODS

This is a cross-sectional study involving 1132 students (age 14-19 years). The following anthropometric variables were measured according to international standards: body mass index (BMI), waist circumference (WC), waist-to-height ratio (WHtR), triceps skinfold thickness (TR), subscapular skinfold (SS), suprailiac skinfold (SI), sum of triceps and subscapular skinfolds (∑TR + SS), and sum of triceps, subscapular and suprailiac skinfolds (∑TR + SS + SI). The BF percentage was calculated using the equations of Lohman (1986) (%FL), Slaughter et al. (1988) (%FS), and Boileau et al. (1985) (%FB).

RESULTS

Except for TR, WC, WHtR and BMI, boys with values for the other anthropometric indicators (SS, SI, ∑TR + SS, ∑TR + SS + SI, %FL, %FS, %FB) above the cutoff point were more likely to have low levels of cardiorespiratory fitness. Girls with values for TR, ∑TR + SS, %FB and %FL above the cutoff points were more likely to have low levels of cardiorespiratory fitness.

CONCLUSIONS

Anthropometric indicators had discriminatory power to identify low levels of cardiorespiratory fitness.

PRACTICE IMPLICATIONS

The reported anthropometric indicators, indexes and equations can be used by healthcare professionals in clinical practice and by school teachers as a simple, fast and inexpensive alternative to identify low levels of cardiorespiratory fitness.

OXYGEN UPTAKE AND INDICATORS OF OBESITY: META-ANALYSIS INCLUDING 17,604 ADOLESCENTS

ABSTRACT Introduction: Low aerobic fitness levels are associated with excess body adiposity in adolescents. However, studies that have analyzed this association in adolescents have used different methods and measures to evaluate aerobic fitness, making it difficult to compare the results. Objective: To conduct a systematic review with meta-analysis of studies that have analyzed the association between aerobic fitness and anthropometric body adiposity indicators in adolescents aged 10-19 years. Methods: A systematic search was performed in May 2016, updated in March 2017, in the following electronic databases: LILACS (BIREME), Embase, MEDLINE (PubMed), Web of Science (Web of Knowledge), Scopus, and SPORTDiscus. Results: Twenty-three studies were selected. The meta-analysis indicated that as the aerobic fitness levels increased, the BMI, waist circumference and body fat percentage values of the adolescents decreased. Conclusion: There is a negative association between aerobic fitness (evaluated by measuring maximum oxygen uptake in the 20-meter Shuttle Run test) and the body fat percentage, BMI and waist circumference of adolescents and a negative association between aerobic fitness (assessed by measuring the number of laps in the 20-meter Shuttle Run test) and body fat percentage. However, caution is required in the interpretation of data due to the heterogeneity of the studies analyzed. Level of Evidence II; Systematic review of studies with level II of evidence.

Hypertension among South African children in disadvantaged areas and associations with physical activity, fitness, and cardiovascular risk markers: A cross-sectional study

Childhood hypertension drives hypertension in later life; hence, assessing blood pressure in children is an important measure to determine current and future cardiovascular health. There is, however, a paucity of childhood blood pressure data, particularly for sub-Saharan Africa. This study explores blood pressure and associations with age, sex, socioeconomic status, physical activity, fitness, and cardiovascular risk markers. In the 'Disease, Activity and Schoolchildren's Health' (DASH) study, a cross-sectional analysis was conducted in disadvantaged neighbourhoods in the Eastern Cape province of South Africa. Assessments included blood pressure, accelerometer-measured physical activity, physical fitness, and cardiovascular risk markers. The study consisted of 785 children (383 boys, 402 girls, M = 12.4±0.9 years). Overall, 18% of the children were classified as hypertensive, while 20% were either overweight/obese, and almost four out of ten children did not meet global daily physical activity recommendations. Hypertensive children were more likely to be overweight/obese, χ² (2,785) = 14.42, p < 0.01, but only if they did not meet physical activity recommendations, χ² (2,295) = 11.93, p < 0.01. Considering the moderating effect which sufficient activity has on the relationship between hypertension and body weight, more emphasis should be placed on early primary health intervention and education strategies.

Longitudinal relationships between changes in body composition and changes in selected metabolic risk factors (abdominal obesity and blood pressure) among South African adolescents

BACKGROUND

Incidence of childhood high blood pressure (BP) is increasing worldwide. This study examined the longitudinal relationship between changes in body composition (i.e. body mass index (BMI), waist circumference (WC) and percentage body fat) and selected metabolic risk factors (abdominal obesity and BP) among adolescents from the Tlokwe municipality in the North West Province of South Africa.

METHOD

One hundred and eight-six adolescents (81 boys and 105 girls) aged 14 to 16 years participated in the study. Body composition was measured following the International Society of the Advancement of Kinanthropometry standard procedures. BMI, abdominal obesity using WC measurement, and resting BP were determined. Analysis of variance (ANOVA) for repeated measures was calculated to determine changes in anthropometric measures and body composition as well as changes in BP. Additionally, Univariate analysis of variance with repeated measures and participants as a random sample was applied. Diastolic BP (DBP) and systolic BP (SBP) were used as dependent variables and sex, age, BMI, WC, and waist-to-height ratio as independent variables.

RESULTS

Significant changes were found for stature, BMI, body mass, WC, SBP, and DBP. BMI for the total group was significant and positively related to abdominal obesity in 2012 (r = 0.55; p < 0.01) and in 2013 (r = 0.77; p < 0.01) and to SBP (r = 0.26; p < 0.05) in 2012 and (r = 0.17; p = 0.43) in 2013. BMI among the boys was significantly and positively related to abdominal obesity in 2012 (r = 0.83; p < 0.01) and 2013 (r = 0.91; p < 0.01). For the girls, BMI was significantly and positively related to abdominal obesity (r = 0.49; p < 0.01) and to SBP (r = 0.32; p = 0.05) in 2012. Boys with a higher WC in 2012 had significantly increased DBP (p < 0.05). Boys measured in 2012 with greater WC and BMI show a significant increase in SBP.

CONCLUSIONS

BMI was positively related to BP and abdominal obesity over time. Relatively high BMI and abdominal obesity significantly increased the likelihood of elevated BP over time, especially in boys. BMI was a predictor of abdominal obesity in boys, while in girls, BMI was a predictor of both abdominal obesity and SBP. In view of the future health implications of both abdominal obesity and elevated BP, urgent strategic interventions programs aimed at increasing physical activity and advocating for well-balanced dietary practices as well as importance of keeping normal blood pressure among South African adolescents are needed.

Cardiorespiratory fitness, adiposity, and ambulatory blood pressure in adolescents

BACKGROUND

This study examined the association of cardiorespiratory fitness (fitness) and adiposity (Body Mass Index [BMI] and waist circumference [WC]) with ambulatory blood pressure (ABP) and tested the moderating effect of adiposity on the association between fitness and ABP.

METHODS

A cross-sectional study was conducted with 370 adolescents aged 11-16 years. Fitness was assessed by a height-adjusted step test and estimated by heart rate recovery, defined as the difference between peak heart rate during exercise and heart rate two minutes postexercise. Adiposity was measured using dichotomized values for percentiles of BMI (≥85th) and WC (≥50th). ABP was measured every 30-60 minutes over 24 hours on a school day. Mixed-effects regression analysis was used.

RESULTS

Each unit increase in fitness was associated with a decrease of systolic blood pressure (SBP) [-0.058 mmHg, P=0.001] and diastolic blood pressure (DBP) [-0.043 mmHg, P<0.001] after adjustment for WC and covariates. Each unit increase in fitness was associated with a decrease in SBP [-0.058 mmHg, P=0.001] and DBP [-0.045 mmHg, P<0.001] after adjustment for BMI and covariates. Fitness and BMI≥85th percentile (or WC ≥ 50th percentile) interactions were not associated with ABP after adjustment for covariates.

CONCLUSIONS

Our findings indicate a small but statistically significant inverse effect of fitness on ABP in adolescents. No evidence of a modifying effect of adiposity on this association suggesting that fitness and weight management have essential roles for maintaining lower ABP in adolescents.

Association Between Sport Participation, Body Composition, Physical Fitness, and Social Correlates Among Adolescents: The PAHL Study

Background: Evidence suggests that social support impacts on participation in sport or physical activity (PA), and is associated with health benefits, although the link is complex and not well understood. The study aim was to examine whether participation in organized sports is related to body composition, physical fitness, and social correlates for PA. Methods: Cross-sectional data on 238 adolescents (90 boys and 148 girls), mean age 14.9 ± 0.8 years, who were participants in the Physical Activity and Health Longitudinal Study, were collected. The participants were divided into two groups: sport participation (SP) and non-sport participation (NSP). Height, weight, and triceps and subscapular skinfolds were assessed according to standard procedures. Weight (kg) and height (m²) were used to calculate body mass index (BMI), and skinfolds were used to calculate body fat percentage. The European Test of Physical Fitness (EUROFIT) battery of tests was used to assess physical fitness. The standardized International Physical Activity Questionnaire Short Form and Social Support for PA questionnaires were used to obtain information on PA and social correlates for PA, respectively. Participants were asked to choose between participation and non-participation in sport. Results: The SP group had lower BMI component values (p = 0.011, d = 0.52 for percentage body fat (%BF); p = 0.011, d = 0.53 for sum of skinfolds (∑SKF) obtained higher physical fitness scores in selected items (p = 0.003, d = 0.64 for sit ups (SUP); p < 0.000, d = 0.96 for maximal oxygen consumption VO₂max) and received higher social support (p < 0.001, d = 0.86 for social support (SS)), than the NSP group. The social support received by those participating in sport correlated positively with most fitness components (p = 0.013, r² = 18% for bent arm hang (BAH); p = 0.000, r² = 12% for sit ups (SUP); p = 0.000, r² = 17% for VO₂max). Physical fitness components were negatively associated with most body composition components for both groups. Conclusions: The results provide a better understanding of sport participation in organized sports-related, body composition-related and physical fitness-related associations with changes in social support received by adolescents and may contribute to the development of more accurate promotive strategies to increase children’s and adolescents’ engagement in sport and PA.

What Physical Fitness Component Is Most Closely Associated With Adolescents' Blood Pressure?

This study aimed to determine which of four selected physical fitness variables, would be most associated with blood pressure changes (systolic and diastolic) in a large sample of adolescents. This was a descriptive and cross-sectional, epidemiological study of 1,117 adolescents aged 14-19 years from southern Brazil. Systolic and diastolic blood pressure were measured by a digital pressure device, and the selected physical fitness variables were body composition (body mass index), flexibility (sit-and-reach test), muscle strength/resistance (manual dynamometer), and aerobic fitness (Modified Canadian Aerobic Fitness Test). Simple and multiple linear regression analyses revealed that aerobic fitness and muscle strength/resistance best explained variations in systolic blood pressure for boys (17.3% and 7.4% of variance) and girls (7.4% of variance). Aerobic fitness, body composition, and muscle strength/resistance are all important indicators of blood pressure control, but aerobic fitness was a stronger predictor of systolic blood pressure in boys and of diastolic blood pressure in both sexes.

Prevalence of elevated blood pressure in children and adolescents in Africa: a systematic review and meta-analysis

BACKGROUND

Despite substantial attention paid to the threat of elevated blood pressure in children and adolescents in high-income countries and the epidemic of hypertension in African adult populations, data on the burden of elevated blood pressure in African children and adolescents have not yet been synthesised. We did a systematic review and meta-analysis to provide estimates of the prevalence of elevated blood pressure and assess associated factors among children and adolescents in Africa.

METHODS

We searched Embase, PubMed, African Journals Online, and African Index Medicus to identify articles published from Jan 1, 1996, to Feb 2, 2017, and searched the reference list of retrieved articles. Each study was independently reviewed for methodological quality. We used a random-effects model to estimate the prevalence of elevated blood pressure across studies and heterogeneity (I²) was assessed via the χ² test on Cochran's Q statistic. This review is registered with PROSPERO, number CRD42015019029.

FINDINGS

We included 51 studies in qualitative synthesis and 25 in the meta-analysis reporting data of a pooled sample of 54 196 participants aged 2-19 years. Study quality was high with only four medium-quality studies and no low-quality studies. Prevalence of elevated blood pressure varied widely across studies (range 0·2-24·8%). The pooled prevalence of elevated blood pressure (systolic or diastolic blood pressure ≥95th percentile) was 5·5% (95% CI 4·2-6·9), whereas that of slightly elevated blood pressure (systolic or diastolic blood pressure ≥90th percentile and <95th percentile) was 12·7% (2·1-30·4). The prevalence of elevated blood pressure was largely associated with body-mass index (BMI), with a prevalence of elevated blood pressure six times higher in obese (30·8%, 95% CI 20·1-42·6) versus normal-weight children (5·5%, 3·1-8·4; p<0·0001).

INTERPRETATION

This study suggests a high prevalence of elevated blood pressure among children and adolescents in Africa, with overweight and obesity being an important risk factor. Efforts to address this burden of elevated blood pressure in children and adolescents should mainly focus on primary prevention at the community level, by promoting healthy lifestyles and avoiding other cardiovascular risk factors, especially overweight and obesity. This study also stresses the need for more elaborate studies using uniform and reliable diagnostic methods to reliably map the burden of elevated blood pressure in children and adolescents in Africa.

FUNDING

None.