Weight gain and sudden infant death syndrome: changes in weight z scores may identify infants at increased risk.

AIMS: To investigate patterns of infant growth that may influence the risk of sudden infant death syndrome (SIDS). DESIGN: Three year population based case control study with parental interviews for each death and four age matched controls. Growth was measured from prospective weight observations using the British 1990 Growth Reference. SETTING: Five regions in England (population greater than 17 million, more than 470 000 live births over three years). SUBJECTS: 247 SIDS cases and 1110 controls. RESULTS: The growth rate from birth to the final weight observation was significantly poorer among the SIDS infants despite controlling for potential confounders (SIDS mean change in weight z score (deltazw) = -0.38 (SD 1.40) v controls = +0.22 (SD 1.10), multivariate: p < 0.0001). Weight gain was poorer among SIDS infants with a normal birth weight (above the 16th centile: odds ratio (OR) = 1.75, 95% confidence interval (CI) 1. 48-2.07, p < 0.0001) than for those with lower birth weight (OR = 1. 09, 95% CI 0.61-1.95, p = 0.76). There was no evidence of increased growth retardation before death. CONCLUSIONS: Poor postnatal weight gain was independently associated with an increased risk of SIDS and could be identified at the routine six week assessment.     

Respiratory control in infants at increased risk for sudden infant death syndrome.

There is much debate relating to possible abnormalities in respiratory control mechanisms in infants considered at increased risk for sudden infant death syndrome (SIDS). The P0.1 occlusion technique was used to assess the central respiratory response to hyperoxic hypercapnia during quiet sleep in 21 normal infants, 13 siblings of SIDS victims, and 17 infants with apparent life threatening events. The slope of P0.1 plotted against carbon dioxide concentration increased exponentially with age, independent of body weight in each group. Birth weight has a significant effect on slope with a lower weight predisposing to a lower slope. Siblings as a group had a significantly lower slope at any given age than normal infants, whereas the infants who had had apparent life threatening events were not significantly different from the controls. As intragroup variation in both siblings and control groups greatly exceeded the significant intergroup differences observed, the technique cannot identify individual infants as belonging to one or other group.     

Identifying infants at risk for sudden infant death syndrome

PURPOSE OF REVIEW: This review examines recent research relevant to the underlying pathophysiology and risk factors for sudden infant death syndrome. RECENT FINDINGS: Current research focuses on the linkage between known risk factors and vulnerability, genetic contributions, and the role of dysfunctional brainstem neurotransmission in the pathogenesis of this syndrome. While social inequalities, prematurity, maternal smoking, infant sleeping practices and sleep environment, arousal failures and environmental pollutants remain important risk factors, new evidence is emerging that certain genetic polymorphisms may contribute to vulnerability. New neuropathological studies have provided strong support for abnormal brainstem serotonergic function. Since serotonin influences a wide range of physiological systems including breathing, the cardiovascular system, temperature, and sleep-wake cycles, this finding strongly supports the hypothesis that sudden infant death syndrome is the result of dysregulation of the autonomic nervous system and provides biological plausibility for certain risk reduction strategies. SUMMARY: Despite a putative diagnostic shift, sudden infant death syndrome remains the most common cause of death from 1 month to 1 year of age. Recent studies confirmed established risk factors and have suggested new genetic vulnerabilities. Finally, new evidence supports a key role for abnormalities in brainstem serotonin systems in the pathophysiology of this syndrome.     

Temperament ratings do not predict arousability in normal infants and infants at increased risk of sudden infant death syndrome

This study sought to determine whether temperament was an indicator of arousability from sleep in infants. We hypothesized that the "threshold" dimension would be the most predictive characteristic because it measures the stimulus intensity required to evoke a discernible response. Healthy term, healthy preterm, and preterm infants with a neonatal history of apnea underwent polysomnography at 2 to 3 months. Arousal was induced using air-jet stimulation of the nostrils in active (AS) and quiet sleep (QS). Temperament was assessed using the Early Infancy Temperament Questionnaire. Arousal thresholds were elevated in QS compared with AS in each group ( <.001), and preterm infants with a neonatal history of apnea were less arousable than healthy preterm infants ( <.05). Temperament was not a predictor of arousability in AS. "Adaptability" was the only significant predictor of arousability in QS. This study demonstrates that temperament characteristics as measured by questionnaire may not be reliable indicators of arousability from sleep.     

Home monitoring for infants at risk of the sudden infant death syndrome

Abstract This study evaluates the effectiveness and social implications of home monitoring of 31 infants at risk of sudden infant death syndrome (SIDS). Thirteen siblings of children dying of SIDS, nine near miss SIDS infants and nine preterm infants with apnoea persisting beyond 40 weeks post conceptual age were monitored from a mean age of 15 days to a mean of 10 months. Chest movement detection monitors were used in 27 and thoracic impedance monitors in four. Genuine apnoeic episodes were reported by 21 families, and 13 infants required resuscitation. Apnoeic episodes occurred in all nine preterm infants but in only five (38%) of the siblings of SIDS (P<0.05). Troublesome false alarms were a major problem occurring with 61% of the infants and were more common with the preterm infants than the siblings of SIDS. All but two couples stated that the monitor decreased anxiety and improved their quality of life. Most parents accepted that the social restrictions imposed by the monitor were part of the caring process but four couples were highly resentful of the changes imposed on their lifestyle.
The monitors used were far from ideal with malfunction occurring in 17, necessitating replacement in six, repair in six and cessation of monitoring in three. The parents became ingenious in modifying the monitors to their own individual requirements
Although none of these 31 'at risk' infants died the study sample was far too small to conclude whether home monitoring prevented any cases of SIDS.     

Theophylline improves pneumogram abnormalities in infants at risk for sudden infant death syndrome

To determine the efficacy of theophylline treatment in infants at increased risk for SIDS, we obtained 24-hour cardiorespiratory recordings (pneumograms) in 80 infants given theophylline in whom the initial pneumogram was abnormal. Fifty-three infants had a clinical diagnosis of near-SIDS, and 27 were asymptomatic siblings with a positive family history for SIDS. The initial pneumogram was obtained at a mean age of 6.9 weeks, and the repeat pneumogram 2.3 weeks later, when the mean theophylline blood concentration was 11.2 +/- 0.5 micrograms/ml. Theophylline treatment resulted in comparable and highly significant improvements in both groups. Among all 80 infants, apnea density decreased from 1.6 +/- 0.2% (SEM) to 0.3 +/- 0.1% (P less than 0.001), periodic breathing episodes/100 minutes decreased from 2.7 +/- 0.4 to 0.3 +/- 0.1 (P less than 0.001), and the longest apneic period decreased from 13.5 +/- 0.7 to 10.1 +/- 0.5 seconds (P less than 0.001). Findings on the pneumogram became completely normal with theophylline therapy in 87% of infants with near-SIDS and 81.5% of asymptomatic siblings. Pneumogram normalization was associated with absence of further symptomatic sleep apnea in the near-SIDS group and with continued absence of any clinical symptoms in the asymptomatic family history group. There were no deaths from SIDS.     

Hypercapnea and hypoxia challenge tests in infants at risk for sudden infant death syndrome

Infants who have almost died of sudden infant death syndrome (SIDS) and infants who are siblings of SIDS victims constitute groups at increased risk for SIDS. Management dilemmas are common among physicians caring for these infants. To assess the usefulness of hypoxia (17% oxygen) and hypercapnea (3% carbon dioxide) challenge tests as predictors of outcome, we reviewed the records of 102 infants who underwent these tests. During hypoxia tests, we found that periodic breathing and respiratory pauses frequently developed among the infants in these high-risk groups, but also developed among control infants. During hypercapnea testing, some infants failed to increase their minute ventilation (usually measured by volume of breath X breaths per minute), but control infants showed this poor response just as often as high-risk infants. Our findings suggest that hypoxia and hypercapnea stress tests are of limited usefulness in planning management of infants at risk for SIDS.     

Home monitoring of infants considered at risk for the sudden infant death syndrome

From 1977 to 1981, 500 infants had been referred to evaluate their risk for the sudden infant death syndrome (SIDS). These included 186 infants who had presented an event (prolonged apnea, hypotonia, pallor or cyanosis) initated while asleep, 133 siblings and 181 controls. All-night polygraphic recordings were performed in all infants, and if indicated by the history of the infants, complementary clinical investigations were done. These procedures led to the identification of 50 infants considered at risk for SIDS (10% of all referrals): 30 near-misses for SIDS, 10 siblings and 10 infants with a minor incident during sleep but with abnormal polygraphic recordings. These 50 infants (group I) were monitored at home during sleep with the help of a cardiac and respiratory monitor. Eight infants not considered at risk were monitored similarly at the request of their parents (group II). Forty of the 50 infants in group I presented with repetitive sleep apneas and bradycardias, and required stimulation by their parents to regain normal cardiorespiratory rhythm. Twelve had to be resuscitated at least once for a life-threatening event. None of the infants in group II showed alarms during sleep. Monitoring could be discontinued after a mean length of 7.2 months for the infants in group I, 4.1 months in group II. It is concluded that if identified in time through adequate investigations, some infants may be protected against SIDS through home monitoring. This approach requires expensive and well trained teams, ready, at any time, to cope with the problems that may arise in the homes of the monitored infants.     

Simplified pneumographic monitoring of infants at risk from sudden infant death syndrome.

A system of pneumographic study of infants considered at increased risk from the sudden infant death syndrome is described. It is simple for nursing staff to use and for clinicians to interpret. A total of 166 ''at risk'' infants were studied and 85 were subsequently monitored at home. Seventeen of these infants, 16 of whom had had abnormal pneumograms, subsequently suffered significant apnoea. Four of 20 babies who had abnormal pneumograms did not have subsequent episodes of apnoea. Two babies died; the first was on a monitor but the second, despite having had an abnormal pneumogram, was not.     

Ventilatory pattern following diphtheria-tetanus-pertussis immunization in infants at risk for sudden infant death syndrome

To evaluate the effects of diphtheria-tetanus-pertussis (DTP) immunization on the ventilatory pattern during sleep in infants at increased risk for sudden infant death syndrome (SIDS), we performed overnight pneumograms (recordings of ventilatory pattern and electrocardiogram) on 30 control infants, 46 infants with unexplained apnea, and 33 subsequent siblings of SIDS victims the night before and the night following a DTP immunization. Pneumograms were quantitated for total sleep time, longest apnea (in seconds), total duration of apneas longer than 6 s (in minutes), and total periodic breathing (in minutes). Following the DTP immunization there was no significant change in any criterion quantitated on pneumograms from any group except for a decrease in periodic breathing in the unexplained apnea group. We conclude that DTP immunization does not increase abnormalities of the ventilatory pattern as recorded by the pneumogram technique in infants at increased risk for SIDS.     

Nocturnal sleep organization in infants "at risk" for sudden infant death syndrome

Nocturnal sleep organization was compared in normal infants and those "at risk" for sudden infant death syndrome (SIDS) (siblings and near-miss infants). Before 12 weeks of age, sleep modifications were observed in "at risk" infants. During their sleep they had a smaller percentage of intervening wakefulness with a higher amount of active sleep. Quiet and active sleep episodes had longer durations resulting in a longer sleep cycle. After 12 weeks, sleep organization tended to normalize. This fact is discussed as a possible factor for a SIDS event: a higher arousal threshold could play a critical role if homeostasy is disturbed during sleep, mainly at an age when the homeostatic control is not fully established.     

Influence of xanthines on gastroesophageal reflux in infants at risk for sudden infant death syndrome

Theophylline and caffeine are two drugs frequently administered to infants at risk for sudden infant death syndrome, because of their stimulatory effects on the respiratory system. These drugs are known to increase gastric acid secretion and to decrease lower esophageal sphincter pressure that, in turn, possibly increases gastroesophageal reflux (GER). Thirty babies were tested for GER before and during caffeine treatment. Eighteen were studied under the same conditions while undergoing theophylline treatment. All results of pH monitoring before treatment were within normal ranges. Episodes of GER increased significantly (P less than .001) in about 50% of the group treated with caffeine and in 66% of the group treated with theophylline. These results were independent of plasma xanthine concentrations (within or below therapeutic ranges) and of the efficacy of the drug. In addition, an increase was noted for the number of episodes of GER in 24 hours (from 5.3 to 17.1 in the caffeine group and from 5.3 to 24.3 in the theophylline group) and for the time pH was less than 4 (from 0.87% to 6% in the caffeine group and up to 13% in the theophylline group). Because GER is another known risk factor for sudden infant death syndrome, the administration of xanthine derivatives in babies at risk for sudden infant death syndrome should be carefully considered in each case.     

Brainstem auditory evoked responses in infants at risk of sudden infant death

Brainstem auditory evoked responses (BAERs) were recorded from 63 near-miss Sudden Infant Death Syndrome (NMSIDS) infants, 26 siblings of SIDS (SSIBS) infants and 67 control infants between 0 and 30 weeks post-term. The majority of BAERs recorded from the NMSIDS and SSIBS infants had normal form and interpeak intervals (V-I and V-IIn) within normal limits for their age. However, 15% of these infants had interpeak intervals outside the normal range, suggesting abnormal neural function in these cases. The distributions of interpeak intervals for all NMSIDS and SSIBS infants were skewed towards longer times compared to control infants. The distributions of V-IIn intervals for both groups of at risk infants were significantly different to that of control infants. While the observations confirm that the recording of BAERs is not suitable for identifying infants at risk of SIDS, they suggest, however, that maturation of neural processing in the brainstem of these infants may be delayed.     

Living at high altitude and risk of sudden infant death syndrome

OBJECTIVE—To investigate the association between altitude of residence and risk of sudden infant death syndrome (SIDS).
METHODS—A retrospective, case control study in the Tyrol, Austria enrolled 99 infants with SIDS occurring between 1984 and 1994, and 136 randomly selected control cases. Data on pregnancy, delivery, child care practice, and sociodemographic characteristics including altitude of residence were collected with a standardised questionnaire.
RESULTS—The risk of SIDS increased gradually with increasing altitude of residence. This relation remained independently significant when the analysis was adjusted for gestational age, birth weight, prenatal care, mother''s age at delivery, educational level of parents, and cigarette smoking during pregnancy. The prone sleeping position emerged as an obligatory cofactor in this association. In the whole of Austria, a similar trend of association emerged between the average altitudes in the 99 political counties and the rates of SIDS.
CONCLUSIONS—This study identified altitude of residence as a significant risk predictor of SIDS, primarily in combination with the prone sleeping position. Respiratory disturbances, reduced oxygen saturation, and lower temperatures at high altitude might explain this association.

     

Living at high altitude and risk of sudden infant death syndrome.

OBJECTIVE: To investigate the association between altitude of residence and risk of sudden infant death syndrome (SIDS). METHODS: A retrospective, case control study in the Tyrol, Austria enrolled 99 infants with SIDS occurring between 1984 and 1994, and 136 randomly selected control cases. Data on pregnancy, delivery, child care practice, and socio-demographic characteristics including altitude of residence were collected with a standardised questionnaire. RESULTS: The risk of SIDS increased gradually with increasing altitude of residence. This relation remained independently significant when the analysis was adjusted for gestational age, birth weight, prenatal care, mother's age at delivery, educational level of parents, and cigarette smoking during pregnancy. The prone sleeping position emerged as an obligatory cofactor in this association. In the whole of Austria, a similar trend of association emerged between the average altitudes in the 99 political counties and the rates of SIDS. CONCLUSIONS: This study identified altitude of residence as a significant risk predictor of SIDS, primarily in combination with the prone sleeping position. Respiratory disturbances, reduced oxygen saturation, and lower temperatures at high altitude might explain this association.     

Adult hemoglobin levels at birth and risk of sudden infant death syndrome

BACKGROUND: During the final weeks of gestation, infants normally begin a transition from the production of fetal to adult hemoglobin. Delayed or faulty transition to the production of adult hemoglobin might play a role in the etiology of sudden infant death syndrome (SIDS). OBJECTIVE: To examine the association between adult hemoglobin levels measured at birth and the subsequent risk of SIDS. DESIGN AND SETTING: Cohort study of all infants born in California between March 1, 1990, and December 31, 1997, who were enrolled in the state's Newborn Screening Program and followed up during the first year of life to identify deaths attributed to SIDS. PARTICIPANTS: Population-based sample of 3.2 million infants. MAIN OUTCOME MEASURE: Risk of death attributed to SIDS. RESULTS: The study included 2425 infants whose deaths were attributed to SIDS. There was an inverse relationship between adult hemoglobin level, expressed as a percentage of total hemoglobin, and the subsequent incidence of SIDS. After adjustment for infant sex, race/ethnicity, length of gestation, maternal age, maternal education, maternal smoking, intrauterine growth restriction, and preeclampsia/eclampsia, the relative risks of SIDS for infants in the lower 4 quintiles of adult hemoglobin level were, in descending order, 1.12 (95% confidence interval [CI], 0.96-1.32), 1.38 (95% CI, 1.19-1.59), 1.55 (95% CI, 1.34-1.80), and 2.15 (95% CI, 1.87-2.47) compared with infants in the highest quintile. CONCLUSIONS: These findings suggest that infants with low levels of adult hemoglobin in the first hours after birth are at elevated risk of SIDS. Delayed maturation in production of adult hemoglobin may play a role in the etiology of some SIDS cases.     

Sleep position and the use of soft bedding during bed sharing among African American infants at increased risk for sudden infant death syndrome

Soft bedding increases the risk for death among prone infants. We compared the softness of beds and bedding and infant sleep position for infants sleeping alone and for those bed sharing. STUDY DESIGN: Questionnaires were used to record the bedding and sleep practices of 218 consecutive African American infants. Enrollment was prospective. Mechanical models were used in the homes of a subgroup to measure the softness of bedding and its propensity to cause rebreathing. Results were compared by using the Student t test, Mann-Whitney U test, and chi(2) analysis. RESULTS: In a cross-sectional sample of infants, at 8.2 +/- 3.3 weeks of age, 61% (133 of 218) had bed shared > or =1 of the previous 14 nights and 48.6% (106 of 218) had bed shared the night before. Breast-feeding rates were not different for bed sharers and those sleeping alone. The rates of maternal smoking for both groups were low (13.6% vs 11.8%). Comforters, pillows, and waterbeds were more commonly used beneath bed-sharing infants. Bed sharers were twice as likely to habitually be placed prone for sleep (18% vs 9%). In the subgroup studied in their homes (13 bed sharing, 19 alone), the shared beds were softer (P <.0001) and could cause more rebreathing (P =.007). CONCLUSIONS: Infants at increased risk for sudden infant death syndrome, by sociodemographic criteria, who also bed share are more likely to sleep prone and to use softer beds. These findings may explain part of the risk associated with bed sharing among US infants, a risk that appears to be independent of the effects of maternal smoking.     

Care of infants with near-miss sudden infant death syndrome

The purpose of this study was to evaluate the effectiveness of home management of life-threatening apnea in infants with near-miss sudden infant death syndrome (SIDS). A total of 84 infants were monitored with apnea monitors for an average of seven months (range 1 to 27). A group of 27 infants had episodes of apnea requiring resuscitation during home monitoring, all of whom were successfully resuscitated by their parents on at least one occasion using bag and mask resuscitation, and 17 infants required more than one resuscitation. Subsequent resuscitation was unsuccessful with four infants. Infants who experienced more than ten episodes of prolonged sleep apnea (apnea longer than 20 seconds) during home monitoring had a significantly increased risk of requiring resuscitation than other infants being studied. With the use of home monitoring of these infants and parents trained in cardiopulmonary resuscitation, the survival rate was 93.4%.