Biomarkers of Stress and Inflammation in Children

Background: Children are increasingly exposed to stressors that can affect their immune function. Given the possible negative effects of stress and inflammation on health, researchers need to use appropriate biomarkers to measure both the effects of stress and subsequent inflammatory responses. Purpose: The purpose of this paper is to briefly review stress and inflammatory pathways, identify biomarkers used to measure chronic stress and chronic inflammation particularly in children in clinical and community settings, and to discuss methodological considerations when measuring stress and inflammation in children. Discussion: Biomarkers of chronic stress can be classified as central, meaning they are made in the brain, or peripheral, meaning they are made in the peripheral tissues in response to central signals. The peripheral biomarker, cortisol, is most frequently used in the community setting. In addition, indirect measures, such as oxytocin, may complement the assessment of stress. Common biomarkers of chronic inflammation in children are C-reactive protein (CRP), TNF-α, and IL-6. Similarly, indirect biomarkers of chronic inflammation, such as IL-2 and IL-1β, may also be considered. Conclusions: Various types of specimens can be used to measure these biomarkers of stress and inflammation including blood, saliva, urine, sweat, hair, nails, and tears. Each type of specimen has different requirements for collection, storage, and assay. Future research would benefit from standardized biomarker levels across age and development in children and incorporation of other biomarkers.

Blunted circadian cortisol in children is associated with poor cardiovascular health and may reflect circadian misalignment

OBJECTIVES

Circadian cues in children (sunlight, exercise, diet patterns) may be associated with health outcomes. The primary objective was to assess associations of daily cortisol fluctuations (morning, night) with cardiovascular health outcomes. A secondary objective was to determine if 1-year longitudinal changes in circadian cortisol levels are associated with longitudinal changes in health outcomes.

STUDY DESIGN

The Cardiovascular Health Intervention Program (CHIP) was a cross-sectional and longitudinal study of cardiovascular risk profiles in public elementary school children in Southern Maine. Participants were 689 students in 4th grade (baseline; age = 9.20 ± 0.41 years), and 647 students in 5th grade (age = 10.53 ± 0.52 years). Longitudinal data (4th and 5th grade) was available for 347 participants. Clinical outcomes were blood pressure, hip/waist ratios, body mass index, percent fat. Laboratory measures were fasting glucose, lipids, and salivary cortisol measures (morning and evening).

RESULTS

Lower first-in-morning diurnal cortisol levels were associated with increased blood pressure (β -0.23 ± 0.05; p < 0.001), increased body fat (β -0.22 ± 0.05; p < 0.001), and poor lipid profiles (β -0.15 ± 0.07; p < 0.05). Inclusion of night cortisol in the model (stress-related) improved associations of the model with bodyfat composition (morning β -0.27 ± 0.05; p < 0.001; night β +0.16 ± 0.06; p < 0.01). Adjustments for potential confounding variables improved associations of morning cortisol with lipids (β -0.19 ± 0.07; p < 0.01). Longitudinal analysis showed that lower morning diurnal cortisol in 4th grade was associated with increases in blood pressure a year later (β -0.18 ± 0.08; p = 0.017) after adjusting for confounding variables.

CONCLUSION

Data presented suggest adding circadian misalignment (lower amplitude of first-in-morning cortisol) to existing models of metabolic syndrome in children. Further, circadian misalignment may be a factor contributing to high blood pressure.

Inclusion of Effect Size Measures and Clinical Relevance in Research Papers

BACKGROUND

There are multiple issues that arise when researchers focus on and only report "statistical significance" of study findings. An important element that is often not included in reports is a discussion of clinical relevance.

OBJECTIVES

The authors address issues related to significance, the use of effect sizes, confidence or credible intervals, and the inclusion of clinical relevance in reports of research findings.

METHODS

Measures of magnitude, precision, and relevance such as effect sizes, confidence intervals (CIs), and clinically relevant effects are described in detail. In addition, recommendations for reporting and evaluating effect sizes and CIs are included. Example scenarios are presented to illustrate the interplay of statistical significance and clinical relevance.

RESULTS

There are several issues that may arise when significance is the focus of clinical research reporting. One issue is the lack of attention to nonsignificant findings in published works although findings show clinical relevance. Another issue is that significance is interpreted as clinical relevance. As well, clinically relevant results from small-sample studies are often not considered for publication, and thus, findings might not be available for meta-analysis.

DISCUSSION

Findings in research reports should address effect sizes and clinical relevance and significance. Failure to publish clinically relevant effects and CIs may preclude the inclusion of clinically relevant studies in systematic reviews and meta-analyses, thereby limiting the advancement of evidence-based practice. Several accessible resources for researchers to generate, report, and evaluate measures of magnitude, precision, and relevance are included in this article.

Recruitment of hard to contact, hard to engage child populations in clinics and schools

Recruiting children with chronic disease or subgroups of children (low income, obese, specific ages, types of cancer) from clinics and schools for research studies may be particularly difficult. While some have deemed such groups as hard to reach, these groups may be more accurately described as either hard to contact or hard to engage. This is not because children are unknown to the school or clinic but because the researcher's ability to communicate directly with targeted children prior to enrollment is limited. The purpose of this paper is to describe barriers and possible strategies for recruiting hard to contact or hard to engage subgroups of children. Barriers identified in recruiting these children were: naïve to research, communication style and technology, parent/guardian burden, parental conditions and concerns, child stressors and distractions, and research setting. Possible strategies include: pre-consent education, information sheets about study, identifying preferred method of communication, meaningful and appropriate incentives, coordinating recruitment visit with regularly scheduled clinic appointments or school schedule, demonstrating research equipment, informing staff about research study, negotiating creatively for space for research, and emphasizing confidentiality of data. Consideration of barriers to recruitment and utilization of strategies to counteract these barriers is critical to the success of a study involving subgroups of children.