Cardiovascular Journal of Africa: Vol 27 No 5 (September/October 2016)

CARDIOVASCULAR JOURNAL OF AFRICA • Volume 27, No 5, September/October 2016

AFRICA

319

Discussion

The increased incidence of CVD risk factors is a growing reality

in children and adolescents, according to studies in several

countries.

1,16,18,24-29

Few studies, however, have been carried out in

African countries. Our study aimed to characterise the current

prevalence and severity of CVD risk factors in pre-pubertal

schoolchildren living in Luanda, Angola. Angola has experienced

rapid economic growth in this century and as observed in other

countries, this fact should translate into a rapid epidemiological

transition affecting the whole population. Studies on this topic

are inadequate in the Angolan population.

Our study shows that the prevalence of overweight and

obesity was approximately 14% in the studied age group and

that fat accumulation correlated with high blood pressure values.

More importantly, we also showed an unexpected elevated

prevalence of dyslipidaemia (mainly high total cholesterol

levels), which, according to our data, was not associated with fat

accumulation.

Similar to other studies in pre-pubertal children,

16,25,26

no significant difference was found between boys and girls

regarding physical and clinical characteristics, indicating that

such differences will appear later on during puberty. Our study

was performed in pre-pubertal children only, to avoid the

confounding influence of sex hormones and fat accumulation on

blood pressure and other cardiovascular risk factors.

It was possible to confirm in this group of children that

borderline or high blood pressure values were associated with

fat accumulation, without significant differences if overall (BMI,

% fat) or central obesity indices (WC) were considered. Some

studies show a stronger association between DBP and central

obesity. However, the small sample size and the relatively small

number of obese and hypertensive children may have hampered

such analysis.

The prevalence of high blood pressure in our cohort was 14.6%

(11.1% with pre-hypertension and 3.5% with hypertension), a

figure similar to that found in other African countries such as

Egypt,

South Africa,

the Seychelles

and Sudan,

as well

as non-African countries, including Spain,

United States,

Canada,

Argentina

and Brazil.

16,27

A study in young adults

(18 to 29 years) in Angola,

however, showed a prevalence

of hypertension of 23%, suggesting a rapid increase in blood

pressure during adolescence and early adulthood.

According to our findings, it is likely that body fat

accumulation during adolescence may contribute to increased

blood pressure, thus contributing to early onset of hypertension

in adults. Validating other findings,

we observed that elevated

blood pressure was higher in overweight and obese children.

Constanzi

et al

. showed that schoolchildren with increased waist

circumference were 2.8 times more likely to have high blood

pressure levels than children with a normal waist circumference.

Hypertension is a multifactorial disease and the pathogenesis

of its relationship with fat accumulation is unknown. Sorof

et al

. showed that obesity-induced hypertension could be due

in part to hyperactivity of the sympathetic nervous system,

which is manifested as increased heart rate and blood pressure

variability.

This association, however, was not identified in our

study since the overweight/obese children showed lower heart

rates at rest.

Another link between increasing blood pressure in children

and fat accumulation is the increased thickness of the intima–

media layer of arteries, leading to increased peripheral vascular

resistance. Wunsch

et al

. showed an increased intima–media

thickness in carotid ultrasonography of obese children. After a

long period of physical activity and substantial weight loss, blood

pressure reduction was followed by a proportional reduction of

the carotid intima–media thickness, as well as in other blood

biochemical parameters.

Genetic and environmental factors have also been suggested

to be linked to high blood pressure. Therefore we also investigated

the association of high blood pressure in children with a familial

history of hypertension. Despite the fact that 72.4% of children

with high blood pressure reported a positive family history

of hypertension, this association was not significant when

compared with children with normal blood pressure and positive

family history of the disease (

0.247;

0.618). Our data are

consistent with those of Shi

et al

who also observed that the

presence of family history of hypertension did not change the

association of high blood pressure and BMI.

Overweight and obesity is a huge health problem in developed

countries, and its prevalence seems to increase rapidly in

countries facing fast economic growth.

Another study by

our group in adults (20–72 years) indicated a prevalence of

overweight and obesity of 29.3 and 19.6%, respectively.

The

increasing incidence of obesity is worrisome, not only because

it represents a disease per se but also because it is an important

risk factor for the development of diabetes and cardiovascular

diseases in the future.

The obesity pandemic therefore predicts the rise in incidence

of other diseases in the near future. For this reason, obesity

should be viewed as one of the most pressing health problems

faced by public health authorities this century.

The prevalence

of obesity, however, has shown variable prevalence in different

countries and in different populations within a single country,

varying from one to 20%.

In our study, we detected excessive weight in 17.7% of the

studied sample, most reaching BMI values compatible with

obesity, without significant gender differences. These figures are

similar to studies in countries such as Egypt,

the Seychelles,

Sudan,

Brazil

16,27,36

and Switzerland,

but differ from others

studies, such as in South Africa, where children living in rural

areas were studied.

Urbanisation therefore seems to be an

important factor facilitating the development of obesity in

children. One feature that distinguishes our results from other

studies was the higher prevalence of obesity than overweight.