SIDS: parental awareness and infant care practices in contrasting socioeconomic areas in Cardiff

Accepted 18 March 1997
Parental awareness of risk factors for sudden infant death syndrome (SIDS) and infant care practices were compared in an area of relative deprivation and one of relative affluence in Cardiff. Awareness was high in both areas. More infants slept on the side in the deprived area (p < 0.02). One in three babies was exposed to cigarette smoking, significantly more in the deprived area (p < 0.001). Health professionals should discourage side sleeping and smoking, especially in areas of deprivation.

     

Social deprivation and the causes of stillbirth and infant mortality

AIMS—To investigate the relation between social deprivation and causes of stillbirth and infant mortality.METHODS—Stillbirths and infant deaths in 6347 enumeration districts in Wales were linked with the Townsend score of social deprivation. In 1993-98 there were 211 072 live births, 1147 stillbirths, and 1223 infant deaths. Poisson regression analysis was used to estimate the magnitude of effect for associations between the Townsend score and categories of death by age and the causes of death. The relative risk of death between most and least deprived enumeration districts was derived.RESULTS—Relative risk of combined stillbirth and infant death was 1.53 (95% CI 1.35 to 1.74) in the most deprived compared with the least deprived enumeration districts. The early neonatal mortality rate was not significantly associated with deprivation. Sudden infant death syndrome showed a 307% (95% CI 197% to 456%) increase in mortality across the range of deprivation. Deaths caused by specific conditions and infection were also associated with deprivation, but there was no evidence of a significant association with deaths caused by placental abruption, intrapartum asphyxia, and prematurity.CONCLUSIONS—Collaborative public health action at national and local level to target resources in deprived communities and reduce these inequalities in child health is required. Early neonatal mortality rates and deaths from intrapartum asphyxia and prematurity are not significantly associated with deprivation and may be more appropriate quality of clinical care indicators than stillbirth, perinatal, and neonatal mortality rates.     

Effect of deprivation on weight gain in infancy

Weights were retrieved from child health records for an annual cohort of 3418 children, aged 18–30 months, to explore the relationship between deprivation and weight gain. Their level of deprivation was classified, using census data for their area of residence, as affluent (11%), intermediate (69%) or deprived (20%). Children from deprived areas were smaller at all ages with a widening gap: by one year of age, they were three times as likely as affluent children to be below the third centile for weight. The thrive index, a measure of the degree of centile shift, showed a slight gain over the first year in affluent and intermediate children, while in deprived children it decreased ( p = 0.001). Deprived children were 2.2 times more likely than intermediate children to have failure to thrive, as manifest by subnormal thrive index values ( p = 0.00008). Unexpectedly, children from affluent areas also showed slightly increased rates. We suggest that this may be explained by higher rates of breast feeding in affluent areas.     

How protective is breast feeding against diarrhoeal disease in infants in 1990s England? A case‐control study

Aims

To assess the effect of several measures of infant feeding on diarrhoeal disease, and whether these effects vary according to markers of social deprivation.

Methods

Case‐control study of diarrhoeal disease cases presenting to 34 general practices in England. Controls were stratified on age group, area deprivation index for the practice, and whether or not the practice was in London. Data were available on 304 infants (167 cases and 137 controls).

Results

After adjustment for confounders, breast feeding was associated with significantly less diarrhoeal disease. Associations were striking even in infants aged ⩾ 6 months. They did not vary by social class, but were greater in those living in rented council accommodation and in more crowded households. The effect of receiving no breast milk was stronger in more deprived areas than in less deprived areas. The effect of not receiving exclusive breast milk was stronger in more deprived areas than in less deprived areas. In formula fed infants, there was significantly more diarrhoeal disease in those not sterilising bottles/teats with steam or chemicals. The protective effect of breast feeding did not persist beyond two months after breast feeding had stopped.

Conclusions

Breast feeding protects against diarrhoeal disease in infants in England although the degree of protection may vary across infants and wear off after breast feeding cessation. Education about the benefits of breast feeding and the risks of inadequate sterilisation should be targeted at carers in deprived areas or households.     

How protective is breast feeding against diarrhoeal disease in infants in 1990s England? A case-control study.

AIMS: To assess the effect of several measures of infant feeding on diarrhoeal disease, and whether these effects vary according to markers of social deprivation. METHODS: Case-control study of diarrhoeal disease cases presenting to 34 general practices in England. Controls were stratified on age group, area deprivation index for the practice, and whether or not the practice was in London. Data were available on 304 infants (167 cases and 137 controls). RESULTS: After adjustment for confounders, breast feeding was associated with significantly less diarrhoeal disease. Associations were striking even in infants aged > or = 6 months. They did not vary by social class, but were greater in those living in rented council accommodation and in more crowded households. The effect of receiving no breast milk was stronger in more deprived areas than in less deprived areas. The effect of not receiving exclusive breast milk was stronger in more deprived areas than in less deprived areas. In formula fed infants, there was significantly more diarrhoeal disease in those not sterilising bottles/teats with steam or chemicals. The protective effect of breast feeding did not persist beyond two months after breast feeding had stopped. CONCLUSIONS: Breast feeding protects against diarrhoeal disease in infants in England although the degree of protection may vary across infants and wear off after breast feeding cessation. Education about the benefits of breast feeding and the risks of inadequate sterilisation should be targeted at carers in deprived areas or households.     

Prevalence of hypospadias and other genital anomalies among singleton births, 1988-1997, in Scotland

BACKGROUND: Considerable debate exists on the epidemiology of genital anomalies. METHODS: All genital anomalies, excluding undescended testes, were identified from neonatal returns, stillbirth and infant death survey records, and returns relating to hospital admissions and linked to form infant profiles on a cohort of singleton births between 1988 and 1997 with follow up for a minimum of three years. FINDINGS: The mean genital anomaly prevalence rate in Scotland was calculated at 4.6 per 1000 births varying from 4.0 per 1000 births in 1988 to 5.9 per 1000 births in 1996. However, there was no evidence of a clear trend to an increasing prevalence of hypospadias, which constituted 73% of the anomalies studied. Logistic regression analysis of the data also showed this rate to be independently associated with being relatively small for gestational age (odds ratio (OR) 1.43, p < 0.001) and increasing maternal age (OR 1.2, p < 0.05). Infants born in deprived areas, as judged by the Carstairs deprivation score, were least likely to have a genital anomaly (OR 0.73, p < 0.01). INTERPRETATION: A new linked register of congenital genital anomalies in Scotland suggests that over a decade, the birth prevalence of genital anomalies has changed little. The associations between genital anomalies, maternal age, and socioeconomic deprivation require further study.     

Social deprivation and the causes of stillbirth and infant mortality.

AIMS: To investigate the relation between social deprivation and causes of stillbirth and infant mortality. METHODS: Stillbirths and infant deaths in 6347 enumeration districts in Wales were linked with the Townsend score of social deprivation. In 1993-98 there were 211 072 live births, 1147 stillbirths, and 1223 infant deaths. Poisson regression analysis was used to estimate the magnitude of effect for associations between the Townsend score and categories of death by age and the causes of death. The relative risk of death between most and least deprived enumeration districts was derived. RESULTS: Relative risk of combined stillbirth and infant death was 1.53 (95% CI 1.35 to 1.74) in the most deprived compared with the least deprived enumeration districts. The early neonatal mortality rate was not significantly associated with deprivation. Sudden infant death syndrome showed a 307% (95% CI 197% to 456%) increase in mortality across the range of deprivation. Deaths caused by specific conditions and infection were also associated with deprivation, but there was no evidence of a significant association with deaths caused by placental abruption, intrapartum asphyxia, and prematurity. CONCLUSIONS: Collaborative public health action at national and local level to target resources in deprived communities and reduce these inequalities in child health is required. Early neonatal mortality rates and deaths from intrapartum asphyxia and prematurity are not significantly associated with deprivation and may be more appropriate quality of clinical care indicators than stillbirth, perinatal, and neonatal mortality rates.     

Coexistence of social inequalities in undernutrition and obesity in preschool children: population based cross sectional study.

AIMS: To test for the coexistence of social inequalities in undernutrition and obesity in preschool children. METHODS: Retrospective, cross sectional, study of routinely collected data from 74 500 children aged 39-42 months in 1998/99. Main outcome measures were weight, height, sex, and age routinely recorded by health visitors. Body mass index (BMI) standardised for age and sex, relative to UK 1990 reference data, was used to define undernutrition (BMI <2nd centile) and obesity (BMI >95th centile; BMI >98th centile). Social deprivation was assessed as Carstairs deprivation category (1 = most affluent to 7 = most deprived). RESULTS: Both undernutrition (3.3%) and obesity (8.5% above 95th centile; 4.3% above 98th centile) significantly exceeded expected frequencies from UK 1990 reference data. Undernutrition and obesity were significantly more common in the more deprived families. Odds ratios in deprivation category 7 relative to category 1 were 1.51 (95% CI 1.22 to 1.87) for undernutrition (BMI <2nd centile) and 1.30 (95% CI 1.05 to 1.60) for obesity (BMI >98th centile). The cumulative prevalence of under and overnutrition (malnutrition) in the most deprived group was 9.5% compared to 6.9% in the least deprived group. CONCLUSIONS: Undernutrition and obesity are significantly more common than expected in young children and strongly associated with social deprivation. Both undernutrition and obesity have adverse short and long term health effects. Public health strategies need to tackle malnutrition (both undernutrition and obesity) in children and take into consideration the association with social deprivation.     

Social trends in singleton births and birth weight in Wirral residents, 1990-2001

OBJECTIVE: To examine social trends in the number of singleton births and birth weight in an English health district between 1990 and 2001, using an area based deprivation index. DESIGN: Analysis of routinely collected hospital data. SETTING: Wirral Health District in north west England. PARTICIPANTS: All 48 452 live births to Wirral residents from 1990 to 2001. MAIN OUTCOME MEASURES: Birth numbers, birth weight, and standard deviation score for birth weights for singleton births. Townsend material deprivation scores derived from postcodes. RESULTS: The number of singleton births fell by 28% over the 12 years. The fall in the least deprived Townsend quartile (45%) was more than triple that in the most deprived quartile (gamma = 0.045; 95% confidence interval (CI) = 0.036 to 0.054; p < 0.001). Over the study period, the mean birth weight in the least deprived Townsend quartile was 141 g higher than in the most deprived quartile. There was a highly significant association between the standard deviation score for birth weight and Townsend quartile (tau-b = -0.062; 95% CI = -0.068 to -0.055; p < 0.001). Numbers of low birth weight babies in the least deprived quartile fell disproportionately compared with those from the most deprived quartile (gamma = 0.17; 95% CI = 0.09 to 0.25; p < 0.001). CONCLUSION: The reduction in birth rate in the Wirral was significantly less in the most deprived districts. This was accompanied by related differences in mean birth weight and the number of low birth weight babies, indicating increasing social inequality in birth trends. Previously described social inequity in birth weight and the number of low birth weight babies continues in the north west of England.     

Breastfeeding in England: time trends 2005–2006 to 2012–2013 and inequalities by area profile

Breastfeeding rates in England have risen steadily since the 1970s, but rates remain low and little is known about area‐based trends. We report an ecological analysis of time trends in area breastfeeding rates in England using annual data on breastfeeding initiation (2005–2006 to 2012–2013) and any breastfeeding at 6–8 weeks (2008–2009 to 2012–2013) for 151 primary care trusts (PCTs). Overall, breastfeeding initiation rose from 65.5% in 2005–2006 to 72.4% in 2012–2013 (average annual absolute increase 0.9%). There was a statistically significantly higher (interaction P < 0.001) annual increase in initiation in PCTs in the most deprived (1.2%) compared with the least deprived tertile (0.7%), and in PCTs with low baseline breastfeeding initiation (2005–2006; 1.4%) compared with high baseline initiation (0.6%). Similar trends were observed when PCTs were stratified by the proportion of teenage mothers and maternal smoking, but not when stratified by ethnicity. Although breastfeeding prevalence at 6–8 weeks also increased significantly over the observed time period (41.2% in 2008–2009, 43.7% in 2012–2013; annual increase 0.7%), there was no difference in the average increase by deprivation profile, ethnicity, teenage mothers and maternal smoking. However, PCTs with low baseline prevalence in 2008–2009 saw a significantly larger annual increase (0.8%) compared with PCTs with high baseline prevalence (0.07%). In conclusion, breastfeeding initiation and prevalence have seen higher increases in areas with low initial breastfeeding, and for initiation, more disadvantaged areas. Although these results suggest that inequalities in breastfeeding have narrowed, rates have plateaued since 2010–2011. Sustained efforts are needed to address breastfeeding inequalities.     

Inequalities in cycle helmet use: cross sectional survey in schools in deprived areas of Nottingham

Aims: To describe cycle helmet owning and wearing among children in a deprived area and to investigate the association between helmet ownership and wearing and socioeconomic deprivation. Methods: Cross sectional survey in 28 primary schools in deprived areas of Nottingham; 1061 year 5 schoolchildren were studied. Results: All year 5 children attending school on the day of the survey completed the questionnaire (87% of children registered at participating schools). Children residing in a deprived area were less likely to own a bike and more likely to ride it four days a week or more. Half the children owned a helmet (52%), but only 29% of these always wore their helmet. Children in deprived areas were less likely to own a helmet, but those that owned a helmet were not less likely to always wear one. Family encouragement and parental warning of dangers of not wearing a helmet were associated with increased helmet ownership rates. Family encouragement and best friends wearing a helmet were associated with higher rates of helmet wearing. Conclusions: Programmes aimed at preventing head injury among child cyclists will need to address the inequality in helmet ownership that exists between children residing in deprived and non-deprived areas. Strategies to increase family encouragement to wear a helmet may be useful, as may those recognising the importance of the attitudes and behaviours of peers, such as peer education programmes. Further work is required to assess how exposure to risk of cycling injury varies with deprivation.     

Inequalities in cycle helmet use: cross sectional survey in schools in deprived areas of Nottingham.

AIMS: To describe cycle helmet owning and wearing among children in a deprived area and to investigate the association between helmet ownership and wearing and socioeconomic deprivation. METHODS: Cross sectional survey in 28 primary schools in deprived areas of Nottingham; 1061 year 5 schoolchildren were studied. RESULTS: All year 5 children attending school on the day of the survey completed the questionnaire (87% of children registered at participating schools). Children residing in a deprived area were less likely to own a bike and more likely to ride it four days a week or more. Half the children owned a helmet (52%), but only 29% of these always wore their helmet. Children in deprived areas were less likely to own a helmet, but those that owned a helmet were not less likely to always wear one. Family encouragement and parental warning of dangers of not wearing a helmet were associated with increased helmet ownership rates. Family encouragement and best friends wearing a helmet were associated with higher rates of helmet wearing. CONCLUSIONS: Programmes aimed at preventing head injury among child cyclists will need to address the inequality in helmet ownership that exists between children residing in deprived and non-deprived areas. Strategies to increase family encouragement to wear a helmet may be useful, as may those recognising the importance of the attitudes and behaviours of peers, such as peer education programmes. Further work is required to assess how exposure to risk of cycling injury varies with deprivation.     

Coexistence of social inequalities in undernutrition and obesity in preschool children: population based cross sectional study

Aims: To test for the coexistence of social inequalities in undernutrition and obesity in preschool children. Methods: Retrospective, cross sectional, study of routinely collected data from 74 500 children aged 39–42 months in 1998/99. Main outcome measures were weight, height, sex, and age routinely recorded by health visitors. Body mass index (BMI) standardised for age and sex, relative to UK 1990 reference data, was used to define undernutrition (BMI <2nd centile) and obesity (BMI >95th centile; BMI >98th centile). Social deprivation was assessed as Carstairs deprivation category (1 = most affluent to 7 = most deprived). Results: Both undernutrition (3.3%) and obesity (8.5% above 95th centile; 4.3% above 98th centile) significantly exceeded expected frequencies from UK 1990 reference data. Undernutrition and obesity were significantly more common in the more deprived families. Odds ratios in deprivation category 7 relative to category 1 were 1.51 (95% CI 1.22 to 1.87) for undernutrition (BMI <2nd centile) and 1.30 (95% CI 1.05 to 1.60) for obesity (BMI >98th centile). The cumulative prevalence of under and overnutrition (malnutrition) in the most deprived group was 9.5% compared to 6.9% in the least deprived group. Conclusions: Undernutrition and obesity are significantly more common than expected in young children and strongly associated with social deprivation. Both undernutrition and obesity have adverse short and long term health effects. Public health strategies need to tackle malnutrition (both undernutrition and obesity) in children and take into consideration the association with social deprivation.     

Changing socioeconomic inequality in infant mortality in Cumbria

Aims: To investigate infant deaths in Cumbria, 1950–93, in relation to individual and community level socioeconomic status. Methods: Retrospective birth cohort study of all 283 668 live births and 4889 infant deaths in Cumbria, 1950–93. Community deprivation (Townsend score) and individual social class were used to estimate socioeconomic status. Logistic regression was used to investigate risk of infant death (early neonatal, neonatal, and postneonatal) in relation to social class and Townsend deprivation score, adjusting for year of birth, birth order, multiple births, and stratified by time period, 1950–65, 1966–75, 1976–85, 1986–93. Results: The risk of infant death in all categories was higher in the lower social classes and more deprived communities, although inequality in risk of neonatal death declined after 1975 to such an extent that there was no significant difference in neonatal death rates by socioeconomic status in the most recent time period. By contrast, there was no narrowing in socioeconomic inequality in postneonatal death risk over the study period. Community deprivation was associated with a significant increased risk of postneonatal death after adjusting for individual level socioeconomic status. Conclusions: Postneonatal deaths remain higher in the most deprived communities and in the more disadvantaged social classes. The social, lifestyle, and environmental determinates of adverse health outcomes for children need to be fully understood, and interventions should be designed and targeted at the more socially deprived sectors of our community.     

Traffic calming policy can reduce inequalities in child pedestrian injuries: database study

OBJECTIVES: To determine whether area wide traffic calming distribution reflects known inequalities in child pedestrian injury rates. To determine whether traffic calming is associated with changes in childhood pedestrian injury rates. DESIGN: Small area ecological study, longitudinal analysis of injury rates with cross sectional analysis of traffic calming and method of travel to school.Settings: Two cities in the United Kingdom. PARTICIPANTS: 4-16 year old children between 1992 and 2000. MAIN OUTCOME MEASURES: Area wide traffic calming distribution by area deprivation status and changes in injury rate/1000. RESULTS: The most deprived fourth of city A had 4.8 times (95% CI 3.71 to 6.22) the number of traffic calming features per 1000 population compared with the most affluent fourth. Injury rates among the most deprived dropped from 9.42 to 5.07 from 1992-94 to 1998-2000 (95% CI for change 2.82 to 5.91). In city B, the traffic calming ratio of the most to least deprived fourth was 1.88 (95% CI 1.46 to 2.42); injury rates in the deprived areas dropped from 8.92 to 7.46 (95% CI for change -0.84 to 3.77). Similar proportions of 9-12 year olds walked to school in both cities. CONCLUSIONS: Area wide traffic calming is associated with absolute reductions in child pedestrian injury rates and reductions in relative inequalities in child pedestrian injury rates.     

Changing socioeconomic inequality in infant mortality in Cumbria.

AIMS: To investigate infant deaths in Cumbria, 1950-93, in relation to individual and community level socioeconomic status. METHODS: Retrospective birth cohort study of all 283,668 live births and 4889 infant deaths in Cumbria, 1950-93. Community deprivation (Townsend score) and individual social class were used to estimate socioeconomic status. Logistic regression was used to investigate risk of infant death (early neonatal, neonatal, and postneonatal) in relation to social class and Townsend deprivation score, adjusting for year of birth, birth order, multiple births, and stratified by time period, 1950-65, 1966-75, 1976-85, 1986-93. RESULTS: The risk of infant death in all categories was higher in the lower social classes and more deprived communities, although inequality in risk of neonatal death declined after 1975 to such an extent that there was no significant difference in neonatal death rates by socioeconomic status in the most recent time period. By contrast, there was no narrowing in socioeconomic inequality in postneonatal death risk over the study period. Community deprivation was associated with a significant increased risk of postneonatal death after adjusting for individual level socioeconomic status. CONCLUSIONS: Postneonatal deaths remain higher in the most deprived communities and in the more disadvantaged social classes. The social, lifestyle, and environmental determinates of adverse health outcomes for children need to be fully understood, and interventions should be designed and targeted at the more socially deprived sectors of our community.     

Unemployment,birthweight, and growth in the first year.

In a cross sectional sample of 655 Glasgow babies the mean birthweight, after adjusting for other factors, of those with unemployed fathers was 150 g less (P less than 0.02) than for babies whose fathers were employed. A longitudinal study of 107 babies from 2 contrasting areas in Glasgow one of which was a socially deprived area was carried out concurrently. The deficit in length of 2.6% for infants from the deprived area at age 12 months was completely explained by adjusting for length at 1 month, father''s height, and father''s employment status (P less than 0.01). The effect of unemployment on the babies'' birthweight was not affected by adjustment for social class. Unemployment may be related to poor infant growth in inner city areas and a national study is needed to see if the recent rise in unemployment has affected this association.     

Heart rate and blood pressure control in infants exposed to maternal cigarette smoking

Aim: Exposure to maternal cigarette smoking is a major risk factor for sudden infant death syndrome (SIDS). Foetal and postnatal smoke‐exposure may alter cardiovascular control in infants. We studied heart rate (HR) and blood pressure (BP) responses in smoke‐exposed infants. Methods: Eleven infants exposed to maternal cigarette smoking were studied at the age of 12 ± 2.1 (range 10–16) weeks. Twenty healthy, age‐matched infants from non‐smoking families served as controls. During confirmed slow‐wave sleep (NREM3), 3–5 sec side motion and 45 sec 45° head‐up tilt tests were performed. Results: Control infants showed consistent biphasic HR and BP responses to side motion, with an initial 2–5% increase followed by a 2% decrease (p < 0.0001). In smoke‐exposed infants, the initial HR (p = 0.009) and BP responses (p < 0.0001) were markedly reduced, and the subsequent decrease in BP was more prominent (systolic blood pressure, SBP, p = 0.005; diastolic blood pressure, DBP, p = 0.03). No differences were observed between the groups in tilt test results, HR variability or HR responses to spontaneous arousals. Conclusion: Maternal cigarette smoking may alter vestibulo‐mediated cardiovascular control in early infancy. This may contribute to increased SIDS risk.     

Socioeconomic inequalities in risk of congenital anomaly

AIMS—To investigate socioeconomic inequalities in the risk of congenital anomalies, focusing on risk of specific anomaly subgroups.METHODS—A total of 858 cases of congenital anomaly and 1764 non-malformed control births were collected between 1986 and 1993 from four UK congenital malformation registers, for the purposes of a European multicentre case control study on congenital anomaly risk near hazardous waste landfill sites. As a measure of socioeconomic status, cases and controls were given a value for the area level Carstairs deprivation index, by linking the postcode of residence at birth to census enumeration districts (areas of approximately 150households).RESULTS—Risk of non-chromosomal anomalies increased with increasing socioeconomic deprivation. The risk in the most deprived quintile of the deprivation index was 40% higher than in the most affluent quintile. Some malformation subgroups also showed increasing risk with increasing deprivation: all cardiac defects, malformations of the cardiac septa, malformations of the digestive system, and multiple malformations. No evidence for socioeconomic variation was found for other non-chromosomal malformation groups, including neural tube defects and oral clefts. A decreasing risk with increasing deprivation found for all chromosomal malformations and Down''s syndrome in unadjusted analyses, occurred mainly as a result of differences in the maternal age distribution between social classes.CONCLUSION—Our data, although based on limited numbers of cases and geographical coverage, suggest that more deprived populations have a higher risk of congenital anomalies of non-chromosomal origin and some specific anomalies. Larger studies are needed to confirm these findings and to explore their aetiological implications.     

Circadian variations in sudden infant death syndrome: associations with maternal smoking, sleeping position and infections. The Nordic Epidemiological SIDS Study

AIM: To study circadian variation in the sudden infant death syndrome (SIDS) and possible associations with risk factors for SIDS. METHODS: A questionnaire-based case-control study matched for place of birth, age and gender was conducted in Denmark, Norway and Sweden: The Nordic Epidemiological SIDS Study. The study comprised 244 SIDS victims and 869 control infants between September 1992 and August 1995. The main outcome was hour found dead. RESULTS: A significant circadian pattern was observed among the 242 SIDS victims with a known hour found dead, with a peak at 08.00-08.59 in the morning (n = 33). Of the SIDS victims, 12% were found dead at 00.00-05.59, 58% at 06.00-11.59, 21% at 12.00-17.59 and 9.0% at 18.00-23.59. When comparing night/morning SIDS and day/evening SIDS (found dead 00.00-11.59 and 12.00-23.59, respectively), the proportion of night/morning SIDS was high among infants of smoking mothers (81% vs 53%, p < 0.001), infants with a reported cold (82% vs 64%, p = 0.007) and infants sleeping side/supine (81% vs 60%, p < 0.001). No associations were observed between hour found dead and other sociodemographic risk factors for SIDS. Risk (odds ratio and 95% confidence interval) of night/morning SIDS and day/evening SIDS was 7.0 (4.5-10.9) and 1.5 (0.8-2.5), respectively, for maternal smoking, 2.2 (1.5-3.1) and 0.6 (0.3-1.3), respectively, if the infant had a reported cold, 3.7 (2.1-6.6) and 3.1 (1.1-8.4), respectively, if the infant was put to sleep in the side position (supine reference), and 11.0 (5.9-20.2) and 21.6 (7.6-60.8), respectively, if the infant was put to sleep in the prone position. CONCLUSION: The observed higher proportion of night/morning cases in SIDS if the mother smoked, if the infant was reported to have a cold and if the infant was sleeping side/supine may contribute to the understanding of some epidemiological characteristics of SIDS.