REVIEW ARTICLE
Has Blood Pressure Increased in Children in
Response to the Obesity Epidemic?
Arnaud Chiolero, MD, MSca, Pascal Bovet, MD, MPHa, Gilles Paradis, MD, MScb, Fred Paccaud, MD, MSca
aCommunity Prevention Unit, Institute of Social and Preventive Medicine, University of Lausanne, Lausanne, Switzerland;bDepartment of Epidemiology, Biostatistics and
Occupational Health, McGill University, Montreal, Quebec, Canada
The authors have indicated they have no financial relationships relevant to this article to disclose.
ABSTRACT
The associations between elevated blood pressure and overweight, on one hand, and the increasing prevalence over time of pediatric overweight, on the other hand, suggest that the prevalence of elevated blood pressure could have increased in children over the last few decades. In this article we review the epidemiologic evidence available on the prevalence of elevated blood pressure in children and trends over time. On the basis of the few large population-based surveys available, the prevalence of elevated blood pressure is fairly high in several populations, whereas there is little direct evidence that blood pressure has increased during the past few decades despite the concomitant epidemic of pediatric overweight. How-ever, a definite conclusion cannot be drawn yet because of the paucity of epide-miologic studies that have assessed blood pressure trends in the same populations and the lack of standardized methods used for the measurement of blood pressure and the definition of elevated blood pressure in children. Additional studies should examine if favorable secular trends in other determinants of blood pressure (eg, dietary factors, birth weight, etc) may have attenuated the apparently limited impact of the epidemic of overweight on blood pressure in children.
www.pediatrics.org/cgi/doi/10.1542/ peds.2006-2136
doi:10.1542/peds.2006-2136
Key Words
blood pressure, hypertension, obesity, trends, epidemiology
Abbreviations
BP— blood pressure CVD— cardiovascular disease NHANES—National Health and Nutrition Examination Survey
Accepted for publication Oct 23, 2006
Address correspondence to Arnaud Chiolero, MD, MSc, Community Prevention Unit, Institute of Social and Preventive Medicine, University of Lausanne, 17 Rue du Bugnon, 1005 Lausanne, Switzerland. E-mail: arnaud. chiolero@chuv.ch
E
LEVATED BLOOD PRESSURE(BP) is one of the leading contributors to the global disease burden worldwideand accounts for 7 million deaths each year.1,2 Several
causes of hypertension operate early in life.3–5In
partic-ular, BP relates, in children as in adults, to body weight,6
dietary factors,7physical activity,8and birth weight.9
Until recently, hypertension was considered to be a
rare condition in children.10 However, because the
worldwide prevalence of pediatric overweight has in-creased largely over the last 2 decades11–13and the
asso-ciation between body weight and BP is well documented in children,3,14–16it is generally believed that BP in
chil-dren should have increased in parallel to the overweight epidemic.6,17
Although the prevalence of type 2 diabetes among children has risen worldwide in parallel to the epidemic of overweight,18,19few reliable population-based data are
available to document trends in BP in children and ad-olescents. A review on trends from 1948 to 1998 re-ported a decline in BP in high-income countries in
chil-dren, adolescents, and young adults aged 5 to 34 years.20
Whether the increasing prevalence of overweight in children has resulted in a commensurate increase in BP is an important issue. Elevated BP acquired in childhood tends to track into adulthood,3and factors that affect BP
in childhood are likely to further increase the burden of hypertension-related diseases in adults.
In this article, we aimed to (1) discuss methodologic and other issues that limit the validity of estimates of elevated BP in children, (2) review the prevalence of elevated BP in children and trends over time on the basis of recent methodologically sound population-based studies, and (3) examine if trends in elevated BP in children seem to reflect the rising prevalence of over-weight.
METHODOLOGIC ISSUES
Limitations Related to BP Estimation in Children
There are several methodologic limitations that compli-cate the valid assessment of BP in children.
A first issue relates to the number of readings on which estimates of “elevated BP” are based. BP decreases over subsequent readings during a single visit as well as over readings taken on separate visits. This decrease partly reflects an alert reaction and is observed in both adults21 and children.15,16It follows that BP obtained at
one occasion tends to overestimate usual BP. Most epi-demiologic studies have relied on only 1 set of BP read-ings obtained at a single visit. It is notable that the normative US reference BP data are based on the first BP
reading obtained at 1 visit.22 However, in most recent
surveys (Table 1), 2 or 3 BP readings were obtained and
BP was based on either the mean of 2 readings,23,24the
mean of 3 readings,25 or the mean of the last 2 of 3
readings.14Normative data recently proposed for English
children were determined on the basis of the mean of the last 2 of 3 readings obtained during a single visit.26
However, when BP was measured on different visits, the prevalence of elevated BP decreased from 19.4% (first visit), to 9.5% (second visit), and to 4.5% (third visit) in
1 American study15and from 8.8% (first visit) to 4.2%
(second visit) in 1 European study.16
The use of different BP-measurement devices also limits the comparability of estimates of elevated BP across studies. Although mercury manometers were used in the past, automated oscillometric devices are now used increasingly often. Electronic devices have several advantages including a greater reliability and the
avoidance of observer bias.27However, proper validation
and calibration of such devices are necessary because substantial systematic bias can exist between different
models and manufacturers.28–30 Unfortunately, few
de-vices have been validated for use in children.31
More-over, current validation protocols are quite lenient and allow, for example, for systematic underestimates or
overestimates of BP by as much as 5 mm Hg.32
The use of the auscultatory technique (mercury or
aneroid) raises specific issues.33 Rounding errors, bias
related to expected values (which may be stronger in children), and other operator-dependant biases can
oc-cur.27 The accuracy of aneroid sphygmomanometers
needs to be checked regularly. Moreover, diastolic BP may be difficult to determine when the Korotkoff sounds do not disappear, which can occur in younger children. The choice of either the fourth Korotkoff phase (K4: muffling of sound, eg, to overcome the problem of nondisappearance of Korotkoff sounds in some children) or the fifth phase (K5: disappearance of sound, as usu-ally applied with adults) to define diastolic BP in children
has important consequences on BP estimates.34 For
ex-ample, in a study of school-aged girls, the mean
differ-ence in BP between K4 and K5 was 9.9 mm Hg.35The US
reference data are based on K5 to define diastolic BP.22
In addition to biases related to BP-measurement pro-cedures, age-adjusted BP in children may be affected by secular trends in children’s height.36BP relates strongly
to height independently of age and gender22,37,38so that
secular increases in children’s height are likely to trans-late into some increase in mean BP levels over time. This issue has relevance in view of the largely different mean heights across populations and the substantial increase in children’s height over time in many populations. In several recent studies of BP trends in the United
States25,39 and United Kingdom,40 the authors did not
adjust BP for height, and part of the observed increase in BP over time might relate to a concomitant increase in children’s height. In an American study, an observed increase in BP between 1986 and 1996 was largely
re-duced when adjusted for weight and height.41 The
TABLE 1 Prevalence of Elevated BP in Recent Large Population-Based Surveys of Children and Adolescents Study (Year) and Sample Age, y Year N Mean BMI or Prevalence of Overweight a,b Device Set of BP Readings Definition of BP Proportion With Elevated Systolic BP, % c Proportion With Elevated Diastolic BP, % c Proportion With Elevated BP, % c Adrogué and Sinaiko 23 (2001); schoolchildren of cities of St Paul and Minneapolis, MN 10–15 1986–1987 19 542 Boys: 20.5 kg/m 2 Girls: 19.9 kg/m 2 Mercury sphygmomanometer First set Second set, if first BP ⱖ 70th percentile d,up to 21 d after first set Mean of 2 readings Mean of 2 readings 2.7 0.8 2.0 0.4 NA NA Jafar et al 25(2005); national random sample, Pakistan 5–14 1990–1994 5641 Boys: 15.2 kg/m 2 Girls: 15.3 kg/m 2 Mercury sphygmomanometer 1 set Mean of 2 readings 8.7 6.2 9.6 3.2 15.8 8.7 Paradis et al 14(2004); random sample, Province of Quebec, Canada 9, 13, and 16 1999 3589 Boys and girls, 9 y: 9% a Boys and girls, 13 y: 9% a Boys and girls, 16 y: 8% a Automated oscillometric Dynamap XL CR 9340 1 set Mean of last 2 of 3 readings
7 13 17 0 0 0 7 13 17
height of children may increase rapidly with socioeco-nomic development.
Current US BP reference data are determined on gen-der-, age-, and height-adjusted percentiles to take body
size into account.22 Reference values have also been
proposed for ambulatory BP and are provided according
to body size directly (by height increments of 5 cm).42
Definition of Elevated BP in Children
Observational studies and clinical trials in adults indicate that BP is associated with both cardiovascular diseases
(CVDs) and total mortality43and that BP reduction
low-ers CVD risk.44 Above 115/75 mm Hg, the risk of CVD
doubles with each increment of 20 mm Hg systolic or 10
mm Hg diastolic BP.45However, because the relationship
between BP and CVD risk is graded over the entire range of BP, a definition of hypertension is inherently arbi-trary. Rose proposed an operational definition of hyper-tension: “the level [of BP] at which the benefits (. . .) of
action exceed those of inaction.”46Among adults,
hyper-tension is currently defined as a sustained BPⱖ140/90
mm Hg and/or current use of antihypertensive treat-ment.45
In children, no cohort data are available to relate BP
with CVD mortality or morbidity.17,47However, elevated
BP in children is associated with several intermediate
outcomes such as ventricular hypertrophy48or increased
carotid intima-media thickness.49–52 Furthermore, BP
tracks from childhood into adulthood, which suggests that elevated BP occurring as early as in childhood may worsen CVD risk in adults. In the Bogalusa Heart Study, BP at age 5 to 14 correlated with BP at age 20 to 31 (correlation coefficients of 0.36 – 0.50 for systolic BP and 0.20 – 0.42 for diastolic BP).53
The most widely used cutoff values for defining ele-vated BP in children are based on BP percentiles specific for gender, age (1-year intervals), and height (7
catego-ries based on height percentiles).22 These norms were
determined on the basis of data in 63 227 American children aged 1 to 17 years who were participating in a variety of studies or surveys in the 1970s and 1980s (ie,
before the current obesity epidemic)12 and were based
on the first BP reading taken during a single occasion.
“Elevated BP” is defined for BP values ⱖ95th gender-,
age-, and height-specific percentile, and a child is con-sidered to be “hypertensive” if he or she has elevated BP on at least 3 separate occasions.22
Pooled data from 6 Northwest European studies con-ducted in 1975–1986, which were based on the first reading taken during a single visit, showed that age-, gender-, and height-adjusted percentiles of systolic/dia-stolic BP were, on average, 6/3 mm Hg higher in
Euro-pean than in American children,54 which underscores
the potential limit of using American reference data for European children.
ELEVATED BP IN CHILDREN AND TRENDS OVER TIME
A literature search was undertaken systematically by one of us (Dr Chiolero) by using the Medline/PubMed database with the search terms “children,” “blood pres-sure,” and “survey.” Chosen articles were restricted to those written in English and published between 1980 and February 2006. References of the selected articles were examined also.
First, we report below (in “Current Prevalence of Elevated BP in Children”) the prevalence of elevated BP that was estimated in the available population-based studies. We selected these population studies if (1) the prevalence of elevated BP was specifically addressed, (2) details about BP measurement were provided, and (3)
US reference data were used22,38to define BP percentiles
and elevated BP (Table 1). In most of these surveys, elevated BP was defined as BP equal to or above the American gender-, age-, and height-specific 95th per-centile (ie, calculated in the 1970s and 1980s, as
ex-plained above).22In addition, the review was limited to
large studies (ⱖ2000 children). Large surveys have the
power to provide prevalence estimates with some preci-sion; because BP varies by age, gender, and height, prev-alence of elevated BP must be examined across a large number of categories of age, gender, and height. Al-though this was not a requirement of the search strat-egy, most of these studies also defined overweight as a BMI equal to or above the American gender- and age-specific 95th percentile. It was noticeable that these ref-erence BMI percentiles were determined on the basis of
data gathered mostly between 1963 and 1980,55a time
period during which overweight was less frequent.12
Second, we report in “Recent Trends of BP in Chil-dren” trends on elevated BP based on single studies. For this purpose, studies were selected it they were based on a cohort study design or on paired surveys, which are suitable to indicate trends over time in mean BP levels or prevalence of elevated BP within defined populations and using comparable BP-measurement procedures (Ta-ble 2).
Current Prevalence of Elevated BP in Children
A convenience sample of American school-aged children aged 10 to 15 years were examined in 1986 –1987 (Table
1).23,56BP was measured with a mercury
sphygmoma-nometer. At the first visit, the prevalence of elevated BP
(ⱖ95th percentile) was 2.0% to 2.7%. Students with BP
⬎70th percentile were seen again on a separate day, and
the prevalence of elevated BP decreased to 0.4% to 0.8%.
On the basis of BP measured during 1 visit in a representative sample, Pakistani children aged 5 to 14
years seen in 1990 –1994 had higher BP24than US
despite a mean BMI that was markedly (⬃3 kg/m2)
lower in Pakistani than American children. The authors speculated that these differences could relate, at least partially, to lower birth weight in Pakistani than US children. Low birth weight is a known risk factor for
subsequent elevated BP in children57and in adults.58
In Quebec, Canada, BP was measured 3 times during 1 visit in 1999 in a representative sample of children
aged 9, 13, and 16 years.14The prevalence of elevated BP
(based on the American reference data) increased across age categories from 7% to 13% and 17%, respectively. The prevalence of overweight was 8% to 9%. Mean BMI
was 4 to 6 kg/m2 higher in children with systolic BP
ⱖ95th percentile than in children with systolic BP
⬍25th percentile. It was noticeable that most children
with elevated BP had only elevated systolic BP. Less than 1% of children with elevated BP had elevated diastolic
BP. Compared with data from an earlier Canadian sur-vey conducted in 1978 –1979, mean systolic BP was 4 to 8 mm Hg higher, whereas mean diastolic BP was 3 to 10 mm Hg lower. However, comparisons are limited be-cause a mercury sphygmomanometer was used in the earlier survey, whereas an automated oscillometric de-vice was used in the latter, and the 2 surveys also had different sampling designs.
Two surveys were conducted at schools in Houston,
Texas, in 2000/200159and 2002.15In both surveys, BP
was measured 3 times during each of up to 3 separate
visits if children had BP ⱖ95th percentile. In the first
survey, the prevalence of overweight was 23% (BMI
ⱖ95th percentile). The prevalence of elevated BP was
16.8% on the basis of readings from the first visit and 9.5% on the basis of readings from the third visit. As in the Canadian study mentioned above, the prevalence of TABLE 2 Trends in BP in Children and Adolescents
Study (Year) and Sample
Age, y Gender Year N Mean BMI or
Prevalence of Overweighta/ Obesityb
Mean BP, mm Hg Mean BP Difference, mm Hg
Comment
Gidding et al64(1995);
biracial samples, Bogalusa, LA
7–9 Boys 1973 109w, 98bl 12.1w, 12.5blkg/m3 97/59w, 96/60bl No adjustment
1984 48w, 52bl 12.9w, 12.7blkg/m3 97/59w, 96/58bl 0/0w, 0/⫺2bl Rohrer index to assess adiposity
Girls 1973 91w, 119bl 12.8w, 12.6blkg/m3 94/57w, 96/59bl
1984 73w, 62bl 13.1w, 13.1blkg/m3 95/59w, 97/60bl ⫹1/⫹2w,⫹1/⫹1bl
15–17 Boys 1981 109w, 98bl 12.5w, 12.6blkg/m3 114/69w, 114/70bl
1992 48w, 52bl 13.5w, 14.1blkg/m3 110/68w, 116/72bl ⫺4/⫺1w,⫹2/⫹2bl
Girls 1981 91w, 119bl 12.9w, 13.5blkg/m3 111/72w, 112/72bl
1992 73w, 62bl 14.2w, 15.5blkg/m3 105/70w, 108/71bl ⫺5/⫺2w,⫺4/⫺1bl
Morrison et al39(1999);
random samples of schoolchildren, Princeton, NJ
10–14 Boys/girls 1973/1974 1989/1990
300 1286
16.9 kg/m2
18.3 kg/m2
98.8/57.7 101.7/59.6
⫹2.9/⫹1.9 No adjustment
Luepker et al41(1999);
schoolchildren, Mineapolis, MN
10–14 Boys 1986 4239 19.7 kg/m2 106.3/63.3 Adjusted for age, ethnicity
1996 5223 20.5 kg/m2 107.8/61.8 ⫹1.5/⫺1.5 No adjustment for height
10–14 Girls 1986 3983 20.3 kg/m2 105.6/66.3
1996 5018 21.2 kg/m2 106.3/64.2 ⫹0.7/⫺1.9
Muntner et al25(2004); 8–17 Boys/girls 1988/1994 3496 11.7%a 104.6/58.4 Adjusted for age, gender,
national random samples, US
1999/2000 2086 16.3%a 106.0/61.7 ⫹1.4/⫹3.3 ethnicity
No adjustment for height
English Health 2–15 Boys 1995 1294 10.9%b 111.7/56.6 No adjustment
Survey40; national 1998 1220 13.0%b 110.3/56.5 ⫺1.4/⫺0.1
random samples, 2001 1072 15.5%b 111.7/57.8 ⫹1.4/⫹1.3
England 2004 669 19.2%b 112.1/57.1 ⫹0.4/⫺0.7
Girls 1995 1279 12.0%b 111.8/57.2
1998 1136 13.8%b 110.3/57.1 ⫺1.5/⫺0.1
2001 1129 14.5%b 110.7/57.8 ⫹0.4/⫹0.7
2004 756 18.5%b 111.8/58.3 ⫹1.1/⫹0.5
Watkins et al65(2004);
random samples, Ireland
12 Boys 1989/1990 247 18.9 kg/m2 111.0/67.9 Adjusted for BMI, age, height,
1999/2001 530 19.4 kg/m2 102.9/59.1 ⫺9.5/⫺9.7 Physical activity score, smoking
Girls 1989/1990 248 19.2 kg/m2 111.5/70.9
1999/2001 514 20.3 kg/m2 104.2/60.4 ⫺10.4/⫺11.9
15 Boys 1989/1990 249 20.4 kg/m2 123.3/73.4
1999/2001 485 20.6 kg/m2 113.2/62.5 ⫺11.6/⫺11.6
Girls 1989/1990 252 21.9 kg/m2 118.3/74.3
1999/2001 482 22.0 kg/m2 109.9/64.5 ⫺8.7/⫺10.2 windicates white;bl, black.
elevated diastolic BP was very low. In the second Hous-ton survey, the prevalence of overweight was 20%. The prevalence of elevated BP was 19.4% on the basis of the readings from the first visit and 4.5% on the basis of the readings from the third visit. BMI was strongly associ-ated with systolic BP but not with diastolic BP. The prevalence of hypertension (defined as elevated BP at all
3 visits) was 10.7% in obese children (BMIⱖ95th
per-centile) compared with 2.6% in children with normal
BMI (⬍85th percentile).
In a school-based study performed in a representative sample of children aged 6 to 11 in 2004 in villages around Milan, Italy, the subjects with elevated BP at the first visit had BP measured again 8 to 15 days later.16The
prevalence of elevated BP decreased from 8.8% at the first visit to 4.2% at the second visit. Both systolic and diastolic BP were associated with BMI.
In Delaware, on the basis of electronic medical charts from children aged 2 to 19 attending primary care prac-tices,60the prevalence of elevated BP (based on only 1 BP
reading for each subject) was surprisingly low (7.2%) despite a very large prevalence of overweight (20.2%;
BMI ⱖ95th percentile). In this study, systolic and
dia-stolic BP were related to BMI at all ages and among
children aged⬍5 in particular.
As part of a school-based surveillance system in chil-dren of the Republic of Seychelles, a rapidly developing small island state in the African region with a large majority of the population of African descent, BP was measured in all children of 4 grades between ages 5 and
16 in 2002–2004.61,62Systolic and diastolic BP were
as-sociated with BMI independent of gender, age, and height. In categories of children with normal weight
(BMI ⬍85th percentile), “at risk of overweight” (BMI
ⱖ85th to⬍95th), and “overweight” (BMIⱖ95th),
pro-portions with elevated BP were 8%, 14%, and 23% in boys and 8%, 16%, and 29% in girls, respectively.
Overall, most of these recent studies reported a high prevalence of elevated BP. However, the prevalence seemed to depend substantially on the methodology used for BP measurement.
Recent Trends of BP in Children
In 2002, McCarron et al20 reviewed data on BP trends
among individuals aged 5 to 34 years of both genders in developed countries. They concluded that BP declined between 1948 and 1998. For individuals aged 18 years or less, conclusions were based mostly on the NHANES for the period of 1963/80 and the English Health
Sur-veys for the short period of 1995/1998.40 In the
NHANES, BP was measured in American youth aged 6 to 17 years and was lower in 1971/1974 and 1976/1980 compared with 1963/1965. However, BP measurements differed between surveys in these periods: BP was mea-sured in either the supine or sitting positions, the ob-server was either a physician or a nurse, and the number
of readings differed between the surveys.19,25,63 In the
NHANES 1971/1974 and 1976/1980 (all measuring with mercury devices), 40% to 50% of the readings had 0 end digits (vs 20% expected if BP was assessed along
recom-mended 2-mm Hg increments).63
In the Bogalusa Heart Study, 2 convenience samples of white and black children aged 7 to 9 were examined
in 1973 and 198464(Table 2). The same children were
examined again 8 years later in 1981 and 1992 at the age of 15 to 17. The mean of 6 BP readings was used, and the fourth Korotkoff sound was recorded for diastolic BP. Only small BP differences were observed among chil-dren aged 7 to 9 in 1973 and 1984. However, chilchil-dren aged 15 to 17 had lower systolic BP in 1992 compared with children of the same age examined in 1981 (except for black boys, who tended to have slightly higher BP in 1992). Only small differences were observed for diastolic BP over time.
In 1973/1974 and 1989/1990, BP was measured in convenience samples of children aged 10 to 14 in
Prince-ton, Ohio.39In 1973/1974, the reported BP was based on
the average of 2 readings, whereas in 1989/1990 it was based on the average of the last 2 of 3 readings. Mean BP was higher in the latter than the former study, whereas the prevalence of elevated BP, surprisingly, tended to decrease. This result may reflect that the distribution of BP did not change uniformly: an increase in the lower range of BP could have occurred without concurrent change in the higher range of BP.
More recently, BP was measured by using the same methods in convenience samples of school-aged children aged 10 to 14 years in 1986 and in 1996 in Minneapolis,
Minnesota.41 During the interval, systolic BP increased,
but diastolic BP decreased. Adjustment for BMI largely eliminated the systolic BP increase between the 2 peri-ods but did not alter the diastolic BP decrease over time. In the recent NHANES surveys (1988/1994 and 1999/ 2000), BP was measured with similar procedures, and 3 BP readings were obtained from most children and ad-olescents aged 8 to 17 years25(Table 2). After adjustment
for age, race/ethnicity, and gender (but not for height), BP was slightly higher in 1999/2000 compared with 1988/1994. Most of the increase in BP over time could not be accounted for by concurrent trends in BMI: ad-justment for BMI could explain only 29% of the increase
in systolic BP and 12% of the increase in diastolic BP.25
In the English Health Surveys,40BP was measured by
BP was only slightly higher in 2004 than in 2001 despite a continued increase in the prevalence of overweight.
In 1989/1990 and 1999/2001, BP was measured in a representative sample of Irish adolescents aged 12 and 15 years with a random-zero Hawksley
sphygmoma-nometer.65The mean of 2 BP readings was used in the
first survey (1989/1990), but only 1 BP reading was measured in the second survey (1999/2001). Mean BMI increased significantly in children aged 12 but increased only marginally in children aged 15. In both age groups, BP decreased substantially between the 2 surveys. Ad-justment for BMI, age, height, birth weight, and social class changed these estimates only marginally. Such a large decrease in BP is difficult to interpret. BP at the second survey was surprisingly low, particularly if one considers that it was based on 1 BP reading, which is usually a source of overestimation.
DISCUSSION
Most recent large population-based surveys have re-ported a relatively high prevalence of elevated BP in children and adolescents in several populations. How-ever, the majority of the few available trend studies suggest that BP increased, at most, only moderately over time since the 1980s, which is in contrast to substantial increases in the prevalence of overweight reported in these same surveys. Some studies even showed a de-crease in BP over time, both small (eg, in the Bogalusa Heart Study64) and substantial (eg, in an Irish study65). In
addition, trends in systolic and diastolic BP were not always consistent. More generally, differences in the methods used to measure BP between studies (hence differences in the definition of “elevated BP”) strongly limited our ability to draw definitive conclusions on BP trends in children over the past few decades.
BMI (or any other index of adiposity) is a major determinant of BP, and the absence of a large increase in BP over time in most studies, despite a rising prevalence of overweight, suggests that other factors may also have influenced trends in BP over time. Such factors may include nutrition characteristics, such as the intake of fruits, vegetables, or dairy products7,66,67 or salt.7,68,69
These dietary factors have not been assessed in most of these studies, and so their independent effect on BP trends cannot be assessed. More generally, whereas the total caloric intake has increased largely in most coun-tries worldwide, mixed trends (favorable and unfavor-able) have been observed for specific nutrients that re-late to hypertension, at least in US children.70–72
Secular changes in nondietary factors may also have impacted on the trends in elevated BP over time. Low birth weight is associated with elevated BP in adults and
children.9,58Mean birth weight has increased throughout
the last quarter century in many countries including the United States, Canada, and the United Kingdom and also
in developing countries such as India73,74despite a
con-comitant increase in preterm births in several of these
countries.75Increasing birth weight over time has been
related to decreasing tobacco use among mothers during
pregnancy,76 increased stature of mothers,73 favorable
changes in socioeconomic factors,73 and other factors
such as improved maternal nutrition. Increasing birth weight over the last decades may have accounted for some of the downward trends in BP over time, but no data currently support this possibility. Breastfeeding has been related to lower BP in children, which can be a result of the low salt content and high long-chain
poly-unsaturated fatty acid content of breast milk.7However,
during the 1990s, breastfeeding practices generally did
not change substantially in many countries worldwide.77
Finally, in many countries, the amount of reported physical activity (particularly walking time or leisure
exercise) has generally decreased.78In addition to being
a risk factor for obesity (itself related to elevated BP), low physical activity is associated independently with higher
BP in children.79 However, precise measurement of all
daily physical activity remains a challenge, as is reliable assessment of trends in physical activity over time.
Our findings are consistent with the review by
Mc-Carron et al,20which reported a decline in BP from 1948
to 1998 in children, adolescents, and young adults in high-income countries. We did not perform a meta-analysis to estimate an average BP change over time in children because of excessively high heterogeneity of data in the available surveys and studies.80First, studies
differ widely in their particulars and design (ethnicity, sample, time period, and, most importantly, methodol-ogy for BP measurement and definition of elevated BP). Second, trends in BP over time may not be assumed to be similar in different populations in view of the differ-ent pace in the pediatric obesity epidemic and possibly also in differences in the relationship between BMI and BP between different populations.
CONCLUSIONS
BP trends should be analyzed by using a life-course
perspective81 (eg, by also considering preconceptional
parental characteristics, pregnancy course, early life characteristics [eg, birth weight], nutrition, and physical activity during childhood and adolescence, socioeco-nomic position at different life stages, etc). The lack of firm evidence linking the epidemic of obesity to the prevalence of elevated BP in children, however, is no reason to weaken efforts to curb the current pediatric epidemic of obesity in view of the numerous detrimental
consequences of overweight on health in children.13,82–84
ACKNOWLEDGMENT
This work was funded partially by Swiss National Sci-ence Foundation grant 3200B0-109999/1.
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STUDIES COUNT COSTS OF BIRTH DEFECTS
“Birth defects lead to more than $2.5 billion a year in hospital costs, according to the first national studies to estimate their financial burden on American families. One study, by researchers at the University of Arkansas and the Centers for Disease Control and Prevention, looked at what hospitals charge—not the actual cost of care. Some conditions were particularly deadly. For example, about 85 percent of babies born with anencephaly, that is, without all or most of their brain and skull, had limited treatment options and died within two days. The average bill for one of these cases was $3800. The most expensive condition was hypoplastic left heart, in which most or all of the two left chambers is missing. Treatment cost about $200 000, on average. A second study, by the Agency for Healthcare Research and Quality, esti-mated what it cost hospitals to care for patients of all ages with birth defects, which it reasoned was about 40 percent of what the hospitals charged. It found that the average age of patients was 17.5 years, the average hospital stay six days, and the average per-stay cost was $18 600. The aggregated cost for all these visits was more than $2.5 billion.”
DOI: 10.1542/peds.2006-2136
2007;119;544
Pediatrics
Arnaud Chiolero, Pascal Bovet, Gilles Paradis and Fred Paccaud
Has Blood Pressure Increased in Children in Response to the Obesity Epidemic?
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DOI: 10.1542/peds.2006-2136
2007;119;544
Pediatrics
Arnaud Chiolero, Pascal Bovet, Gilles Paradis and Fred Paccaud
Has Blood Pressure Increased in Children in Response to the Obesity Epidemic?
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