Prevalence of elevated BP in children has risen over time and is associated with sodium intake

Rosner B, Cook NR, Daniels S, Falkner B
Hypertension July 15, 2013, doi: 10.1161/​HYPERTENSIONAHA.111.00831

Background

The prevalence of obesity has been increasing over the past 2 decades, in both children and adolescents. Sodium intake is also high, with a majority of children taking more than the Reference Daily Intake (RDI) [1]. Since body mass index (BMI) and sodium intake are important risk factors for hypertension in adults, it is reasonable to expect corresponding increases in prevalence of elevated blood pressure (BP) in children.
National Health and Nutrition Examination Survey (NHANES) III and continuous NHANES have previously studied mean blood pressure (BP) levels and prevalence of hypertension and prehypertension in children [4-6]. Small sample sizes have been a recurrent issue in previous studies. This article used the NHANES population, and estimated percentiles using norms based on normal-weight children [5], rather than the Pediatric Task Force Standard [6]. This yielded a higher number of hypertension and prehypertension children. Data from NHANES III (1988-1994) and continuous NHANES (NHANES 1999–2000, 2001–2002, 2003–2004, 2005– 2006, 2007–2008, here referred to as the NHANES 1999 to 2008 population), reflecting 11636 subjects aged 8-17 years old, were used.

Main results

• Both boys (55.1+0.5 vs 52.7+0.9 kg, P=0.016) and girls (52.1+0.4 vs 49.4+0.7 kg, P<0.001) showed a significant increase in weight as well as BMI (boys: 21.3+0.1 vs 20.6+0.2 kg/m³, P=0.004, girls: 21.6+0.1 vs 20.6+0.2 kg/m³, P<0.001) in NHANES 1999-2008 vs. NHANES III, and large increases in waist circumference were seen for boys (75.4+0.3 vs. 72.3+0.3 cm, P<0.001) and especially for girls (75.2+0.4 vs. 70.6+0.5 cm, P<0.001).
• Mean systolic BP (SBP) significantly increased in boys (107.8 vs. 106.1 mmHg, P=0.001), but not diastolic BP (DBP)(56.7 vs. 57.7 mmHg, P=0.13). In girls, both SBP (104.9 vs. 102.3 mmHg, P<0.001) and DBP (59.0 vs. 57.0 mmHg, P=0.003) had increased in NHANES 1999-2008 as compared to in NHANES III.
• Significant positive associations were seen between prevalence of high BP and elevated Na intake (>3450 vs. <2300 mg, OR: 1.37, P(trend)=0.038) and reduced carbohydrate intake (<200 vs. > 300 g, OR: 1.33, P(trend)=0.021.). After correction for BMI and waist circumference, only Na intake remained statistically significantly associated with elevated BP (>3450 vs. <2300 mg, OR: 1.36, P=0.024, 2301 vs. 3450 mg: OR: 1.17, P=0.21, P(trend across all 3 NA categories): 0.045. Both BMI and waist circumference independently contributed to the prevalence of elevated BP.
• The crude prevalence of elevated BP was significantly higher in NHANES 1999-2008 than in NHANES III (OR: 1.39, P0.007). The association changed little after adjusting for age, sex and race/ethnicity (OR: 1.38, P=0.009). However, the association weakened after corrections for BMI and waist circumference (OR: 1.25, P=0.089), reflecting the increase in obesity over time. Further adjustment for Na intake slightly strengthened the association ((OR: 1.27, P-0.069), which reflects the mild reduction in percentage of children with >1.5 RDI (>3450mg and >2000 calories) in NHANES 1999-2008 vs. NHANES III.

Conclusion

Overall roughly one third of the excess prevalence of elevated BP in NHANES 1999-2008 vs. NHANES III can be accounted for by differences in known risk factors. An association between high Na intake and elevated BP in childhood was observed, which calls for strategies to reduce Na intake.

Editorial comment [7]

This report demonstrates an association between high Na intake and elevated BP, which was stronger among the overweight/obese subjects. This offers relevant information fur future preventive strategies. Inclusion of prehypertension is relevant, since evidence is accumulating that is is not entirely benign with regard to future cardiovascular disease risk.
It should be noted that sodium intake was assessed using a single 24-hour recall, without validation. A change in ethnic distribution was seen between the different surveys, which could affect outcomes. Furthermore, other lifestyle factors were not accounted for. Nevertheless, this study provides support for public health strategies to reduce weight and salt intake in childhood, to reduce future high BP prevalence among children and adolescents.  

References

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