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Stress in infants and parents: Studies of salivary cortisol, behaviour and psychometric measures
Linköping University, Department of Clinical and Experimental Medicine, Pediatrics . Linköping University, Faculty of Health Sciences.ORCID iD: 0000-0002-3256-5407
2006 (English)Doctoral thesis, comprehensive summary (Other academic)
Abstract [en]

The life of a preterm infant admitted to a neonatal intensive care unit may be stressful from the moment of birth. Ever since Hans Selye’s initial characterisation of the biological stress response, cortisol has been frequently measured as an indicator of stress responsivity. However, research of the stress response and cortisol in infants, especially those who are preterm and/or ill, has been scarce basically because of methodological issues.

The first aim with this thesis was to investigate the acute stress response, as measured by salivary cortisol and behaviour, for preterm infants, healthy infants, and infants at high psychosocial risk in response to certain defined handling procedures. The second aim was to investigate the stress response, as measured by salivary cortisol and psychometric measures, for parents present during the handling procedure of their infants. The intention was to perform all investigations in an as naturally occurring situation as possible, which means that the studied procedures would have been performed irrespectively of the research.

The present thesis includes six original articles. The results of the first study demonstrate that it is feasible to collect sufficient amounts of saliva and to analyse salivary cortisol in neonates using the presented method of collection and analysis. The second study shows that preterm infants, usually cared for in incubators, show no signs of discomfort and have variable cortisol responses during skin-to-skin care with their mothers. The mothers, however, experience stress and low control before their first skin-to-skin care with their preterm infant and do not relax completely until after the session. In the third study we found that preterm infants have higher baseline salivary cortisol as compared to healthy full-term infants. Moreover, preterm infants have higher and sustained pain response during a nappy change as compared to healthy full-term infants. The results of the fourth study shows that infants younger than three months, living in psychosocial high-risk families, have increased cortisol responses during a nappy change, performed by the mother. However, support with the aim of improving mother-infant interaction, dampens the stress response. The results of the fifth study show that oral sweet-tasting solution in combination with a pacifier dampen the levels of the stress hormone cortisol in three months old infants during routine immunisation. Moreover, parents experience more self-rated emotional stress before immunisation if it is their first child who is being immunised. The sixth paper shows that the material used for saliva collection (cotton buds with wooden or plastic sticks) is of importance when saliva is collected but for practical reasons not centrifuged within 24 hours prior to cortisol analyse.

The present thesis shows that it is practically feasible to collect saliva and to analyse the stress hormone cortisol in infants. The interpretation of infants’ and parents’ salivary cortisol responses to different handling procedures are discussed in relation to shortand long-term consequences, neonatal intensive care, preterm birth, attachment, mood, and pain.

Place, publisher, year, edition, pages
Institutionen för molekylär och klinisk medicin , 2006.
Series
Linköping University Medical Dissertations, ISSN 0345-0082 ; 943
Keyword [en]
Stress, Infants, Prematura childern, Intensive care, neonatal, saliva, Chemistry, Glucose, Hydrocortisone
National Category
Pediatrics
Identifiers
URN: urn:nbn:se:liu:diva-7294ISBN: 91-85497-78-9 (print)OAI: oai:DiVA.org:liu-7294DiVA: diva2:22319
Public defence
2006-05-12, Berzeliussalen, Ingång 65, Campus US, Linköpings universitet, Linköping, 09:00 (English)
Opponent
Supervisors
Available from: 2006-09-07 Created: 2006-09-07 Last updated: 2016-05-04
List of papers
1. Salivary cortisol and administration of concentrated oral glucose in newborn infants: improved detection limit and smaller sample volumes without glucose interference
Open this publication in new window or tab >>Salivary cortisol and administration of concentrated oral glucose in newborn infants: improved detection limit and smaller sample volumes without glucose interference
2004 (English)In: Scandinavian Journal of Clinical and Laboratory Investigation, ISSN 0036-5513, Vol. 64, no 2, 113-118 p.Article in journal (Refereed) Published
Abstract [en]

Newborn infants are subject to repetitive painful and stressful events during neonatal intensive care. When the baby attempts to cope with a stressful situation the hypothalamus-pituitary-adrenal axis is activated, releasing cortisol. The free cortisol response is optimally measured in saliva and saliva samples can be taken easily and without pain. However, saliva is very scarce in infants and saliva stimulants can interfere with analytical methods. Nowadays, sweet solutions are frequently administered to neonates prior to a disturbing procedure in order to reduce pain. The possible interference of sweet solutions with the measurement of salivary cortisol has not yet been documented. The aims of the present study were to further improve the detection limit of the radioimmunoassay used for cortisol analysis and to determine the degree of interference of high concentrations of glucose with the analytical method. By decreasing incubation temperature and prolonging the incubation time it was possible to improve the detection limit of the radio immunoassay (RIA) to 0.5 nmol/L at the same time as the sample volume was decreased to 10 μL saliva. Saliva was collected from full-term and preterm babies and was sufficient for analysis in 113 out of 116 (97%) samples. Glucose in the concentrations and amounts commonly used for pain relief did not interfere with the RIA method. In conclusion, it is feasible to collect microlitre volumes of saliva and analyse even very low concentrations of cortisol in newborns. It is also possible to offer the baby oral glucose prior to a painful procedure and still reliably measure salivary cortisol.

Keyword
Glucocorticoid, neonate, pain, radioimmunoassay, saliva, stress, stress hormone, sweet solution
National Category
Medical and Health Sciences
Identifiers
urn:nbn:se:liu:diva-13951 (URN)10.1080/00365510410004452 (DOI)
Available from: 2006-09-07 Created: 2006-09-07 Last updated: 2016-05-04
2. Salivary cortisol and mood and pain profiles during skin-to-skin care for an unselected group of mothers and infants in neonatal intensive care
Open this publication in new window or tab >>Salivary cortisol and mood and pain profiles during skin-to-skin care for an unselected group of mothers and infants in neonatal intensive care
2005 (English)In: Pediatrics, ISSN 0031-4005, Vol. 116, no 5, 1105-1113 p.Article in journal (Refereed) Published
Abstract [en]

Objectives. Mother-infant separation after birth is a well-known source of stress. Parents and preterm infants in neonatal intensive care are separated immediately after birth. Skin-to-skin care is 1 possible method to reduce the separation-dependent stress. The aim of the present study was to investigate how skin-to-skin care influences stress for the mother and the infant in neonatal intensive care.

Methods. Seventeen mother-infant pairs were included at their first and fourth skin-to-skin care. The infants were 25 to 33 weeks' gestational age, with birth weights ranging from 495 to 2590 g. In mothers, salivary cortisol, heart rate, mood scale, and stress measured on a visual analog scale (VAS) were analyzed. In infants, salivary cortisol and heart rate were analyzed, and because pain is one facet of stress, 2 different pain scales were used.

Results. In mothers, the skin-to-skin care decreased salivary cortisol (32%), heart rate (7%), and VAS (89%), whereas mood increased (6%). Before the fourth skin-to-skin care, mothers rated less stress on VAS, and salivary cortisol and heart rate improved faster. The infants' cortisol either increased or decreased. Their heart rates and pain scores decreased during skin-to-skin care.

Conclusions. Our results lend additional support to the value of skin-to-skin care in neonatal intensive care. Variable stress responses in preterm infants favor the need for individualized care. The mothers' need for support seem to be more pronounced in the first skin-to-skin session as our results show a higher degree of stress as compared with later skin-to-skin care.

Keyword
cortisol, newborn infant, maternal behavior, pain measurement, stress
National Category
Medical and Health Sciences
Identifiers
urn:nbn:se:liu:diva-13952 (URN)10.1542/peds.2004-2440 (DOI)
Available from: 2006-09-07 Created: 2006-09-07 Last updated: 2016-05-04
3. Is a nappy change stressful to neonates?
Open this publication in new window or tab >>Is a nappy change stressful to neonates?
Show others...
2006 (English)In: Early Human Development, ISSN 0378-3782, E-ISSN 1872-6232, Vol. 82, no 10, 669-676 p.Article in journal (Refereed) Published
Abstract [en]

Objectives

Infants in neonatal intensive care (NICU infants) are often cared for in a stressful environment that includes potentially painful or stressful interventions. The aim was to investigate whether NICU infants have different pattern of stress and pain responses than healthy newborns when challenged by a non-painful everyday care routine.

Methods

NICU infants born at 23–38 weeks gestation (n = 39) were compared to healthy full-term newborns (n = 30). Cortisol concentrations in saliva were determined before and 30 min after a standardised nappy change. The premature infant pain profile (PIPP) and the neonatal infant pain scale (NIPS) were evaluated before, during, directly after, 3 min after, and 30 min after the nappy change. The investigation was performed on two different occasions, first between postnatal days 2–7 and then between postnatal days 10–18.

Results

NICU infants had higher median baseline salivary cortisol levels compared to full-term newborns on both occasions (17.1 nmol/L vs. 6.2 nmol/L p < 0.01 and 8.5 nmol/L vs. 2.4 nmol/L p < 0.01, respectively). Salivary cortisol decreased in response to the second nappy change in NICU infants (p = 0.01). NICU infants had higher PIPP scores during both nappy changes (p < 0.001 for both occasions) and more sustained increases in PIPP and NIPS up to 30 min after the nappy changes compared to full-term newborns.

Conclusions

NICU infants have higher baseline salivary cortisol than healthy full-term newborns. There is a change in baseline cortisol by age in both groups. Full-term infants as well as NICU infants show an increased pain response to a standardised nappy change.

Keyword
Cortisol; Infant; Newborn; Neonatal intensive care; Pain measurement; Stress
National Category
Medical and Health Sciences
Identifiers
urn:nbn:se:liu:diva-13953 (URN)10.1016/j.earlhumdev.2005.12.013 (DOI)
Available from: 2006-09-07 Created: 2006-09-07 Last updated: 2016-05-04Bibliographically approved
4. Salivary cortisol response in mother-infant dyads at psychosocial high-risk
Open this publication in new window or tab >>Salivary cortisol response in mother-infant dyads at psychosocial high-risk
2006 (English)In: Child Care Health and Development, ISSN 0305-1862, Vol. 33, no 2, 128-136 p.Article in journal (Refereed) Published
Abstract [en]

Objectives The aim of the present study was to investigate the adrenocortical response to diaper change in mother–infant dyads with psychosocial risk factors.

Material and methods Twenty-two mother–infant pairs with well-defined psychosocial problems were included. The mother–infant pairs were treated for 6 weeks in a daycare programme to improve attachment. Salivary cortisol was measured before and after a diaper change during the first and last weeks of enrolment in the programme. Mothers' sensitivity towards their infants' signals was measured using a scale from 1 (highly insensitive) to 9 (highly sensitive) according to Ainsworth.

Results Median salivary cortisol increased in 15 out of 22 infants after the first diaper change. The increase was most pronounced in the group of infants below 3 months of age (n = 15) where median salivary cortisol increased 170% after the first diaper change (P < 0.05) and decreased 19% after the last diaper change (not significant). Out of these 15 infants, 11 showed an increase in salivary cortisol in response to the first diaper change while four out of 15 did so in response to the last diaper change (P < 0.05). The salivary cortisol response did not change over time in infants aged 3 months or above. A mother's sensitivity to her child increased significantly (P < 0.001) from the first to the last week. In mothers, median salivary cortisol decreased 38% after the first diaper change (P < 0.05) and 57% after the last diaper change (P = 0.001).

Discussion A diaper change is normally not perceived as stressful. The stress response caused by a diaper change may illustrate an insufficiency in the mother–infant relationship before treatment. Professional support improved the mothers' sensitivity and stabilized the stress response to diaper change in the youngest infants.

Keyword
attachment, cortisol, infant, psychosocial risk-mothers, stress
National Category
Medical and Health Sciences
Identifiers
urn:nbn:se:liu:diva-13954 (URN)10.1111/j.1365-2214.2006.00637.x (DOI)
Available from: 2006-09-07 Created: 2006-09-07 Last updated: 2016-05-04
5. Stress at three-month immunization: A randomized, placebo-controlled trial of parents’ and infants’ salivary cortisol response in relation to the use of pacifi er and oral glucose
Open this publication in new window or tab >>Stress at three-month immunization: A randomized, placebo-controlled trial of parents’ and infants’ salivary cortisol response in relation to the use of pacifi er and oral glucose
Manuscript (Other academic)
Identifiers
urn:nbn:se:liu:diva-13955 (URN)
Available from: 2006-09-07 Created: 2006-09-07 Last updated: 2010-01-13
6. Saliva collection using cotton buds with wooden sticks: a note of caution
Open this publication in new window or tab >>Saliva collection using cotton buds with wooden sticks: a note of caution
2006 (English)In: Scandinavian Journal of Clinical and Laboratory Investigation, ISSN 0036-5513, Vol. 66, no 1, 15-18 p.Article in journal (Refereed) Published
Abstract [en]

The aims of the present study were to investigate whether the cotton-tipped applicators (cotton buds) used to collect saliva in infants can be stored un-centrifuged prior to cortisol analysis, and to test whether there is any difference in results between wooden and plastic-shafted sticks. Saliva was collected from 10 healthy adults using 6 cotton buds, i.e. 3 with wooden sticks and 3 with plastic sticks. The samples were then centrifuged at three different time-points: immediately after collection, after 24 h and after 48 h. Using cotton buds with wooden sticks, median salivary cortisol was significantly lower after 24 h (40 %) (p<0.001) and after 48 h (49 %) (p<0.001) of storage than it was of the samples centrifuged immediately. There was no significant difference between the samples centrifuged immediately and those centrifuged after 24 h and 48 h when saliva was collected using the cotton buds with plastic sticks. It is concluded that cotton buds with wooden sticks should not be used in studies of salivary cortisol unless it is possible to centrifuge the saliva immediately. Moreover, it is inadvisable to alternate between cotton buds with wooden and plastic sticks in the same study when collecting saliva for analysis of cortisol.

Keyword
Cortisol; neonate; plastics; stress
National Category
Medical and Health Sciences
Identifiers
urn:nbn:se:liu:diva-13956 (URN)10.1080/00365510500402166 (DOI)
Available from: 2006-09-07 Created: 2006-09-07 Last updated: 2016-05-04

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