Infant Sleep Hazards and the Risk of Sudden Unexpected Death in Infancy

OBJECTIVE

To examine the effects of infant sofa-sleeping, recent use by caregivers of alcohol, cannabis, and/or other drugs, and bed type and pillows, on the risk of sudden unexpected death in infancy (SUDI) in New Zealand.

STUDY DESIGN

A nationwide prospective case-control study was implemented between March 2012 and February 2015. Data were collected during interviews with parents/caregivers. "Hazards" were defined as infant exposure to 1 or more of sofa-sleeping and recent use by caregivers of alcohol, cannabis, and other drugs. The interaction of hazards with tobacco smoking in pregnancy and bed sharing, including for very young infants, and the difference in risk for Māori and non-Māori infants, also were assessed.

RESULTS

The study enrolled 132 cases and 258 controls. SUDI risk increased with infant sofa-sleeping (imputed aOR [IaOR] 24.22, 95% CI 1.65-356.40) and with hazards (IaOR 3.35, 95% CI 1.40-8.01). The SUDI risk from the combination of tobacco smoking in pregnancy and bed sharing (IaOR 29.0, 95% CI 10.10-83.33) increased with the addition of 1 or more hazards (IaOR 148.24, 95% CI 15.72-1398), and infants younger than 3 months appeared to be at greater risk (IaOR 450.61, 95% CI 26.84-7593.14).

CONCLUSIONS

Tobacco smoking in pregnancy and bed sharing remain the greatest SUDI risks for infants and risk increases further in the presence of sofa-sleeping or recent caregiver use of alcohol and/or cannabis and other drugs. Continued implementation of effective, appropriate programs for smoking cessation, safe sleep, and supplying safe sleep beds is required to reduce New Zealand SUDI rates and SUDI disparity among Māori.

The combination of bed sharing and maternal smoking leads to a greatly increased risk of sudden unexpected death in infancy: the New Zealand SUDI Nationwide Case Control Study

BACKGROUND

Despite a major reduction in overall infant mortality, sudden unexpected death in infancy (SUDI) continues to be of concern in New Zealand, as the rate is high by international standards, and is even higher in indigenous Māori.

AIM

To identify modifiable risk factors for SUDI.

METHODS

A three-year (1 March 2012-28 February 2015) nationwide case-control study was conducted in New Zealand.

RESULTS

There were 137 SUDI cases, giving a SUDI mortality rate of 0.76/1,000 live births. The rate for Māori was 1.41/1,000, Pacific 1.01/1,000 and non-Māori non-Pacific (predominantly European) 0.50/1,000. The parent(s) of 97% of the SUDI cases were interviewed. Six hundred and forty-nine controls were selected and 258 (40%) were interviewed. The two major risk factors for SUDI were: maternal smoking in pregnancy (adjusted OR=6.01, 95% CI=2.97, 12.15) and bed sharing (aOR=4.96, 95% CI=2.55, 9.64). There was a significant interaction (p=0.002) between bed sharing and antenatal maternal smoking. Infants exposed to both risk factors had a markedly increased risk of SUDI (aOR=32.8, 95% CI=11.2, 95.8) compared with infants not exposed to either risk factor. Infants not sharing the parental bedroom were also at increased risk of SUDI (aOR=2.77, 95% CI=1.45, 5.30). Just 21 cases over the three-year study were not exposed to smoking in pregnancy, bed sharing or front or side sleeping position.

CONCLUSIONS

This study has shown that many of the risk factors that were identified in the original New Zealand Cot Death Study (1987-1989) are still relevant today. The combination of maternal smoking in pregnancy and bed sharing is extremely hazardous for infants. Furthermore, our findings indicate that the SUDI prevention messages are still applicable today and should be reinforced. SUDI mortality could be reduced to just seven p.a. in New Zealand (approximately one in 10,000 live births).

Sodium exclusion QTL associated with improved seedling growth in bread wheat under salinity stress

Worldwide, dryland salinity is a major limitation to crop production. Breeding for salinity tolerance could be an effective way of improving yield and yield stability on saline-sodic soils of dryland agriculture. However, this requires a good understanding of inheritance of this quantitative trait. In the present study, a doubled-haploid bread wheat population (Berkut/Krichauff) was grown in supported hydroponics to identify quantitative trait loci (QTL) associated with salinity tolerance traits commonly reported in the literature (leaf symptoms, tiller number, seedling biomass, chlorophyll content, and shoot Na(+) and K(+) concentrations), understand the relationships amongst these traits, and determine their genetic value for marker-assisted selection. There was considerable segregation within the population for all traits measured. With a genetic map of 527 SSR-, DArT- and gene-based markers, a total of 40 QTL were detected for all seven traits. For the first time in a cereal species, a QTL interval for Na(+) exclusion (wPt-3114-wmc170) was associated with an increase (10%) in seedling biomass. Of the five QTL identified for Na(+) exclusion, two were co-located with seedling biomass (2A and 6A). The 2A QTL appears to coincide with the previously reported Na(+) exclusion locus in durum wheat that hosts one active HKT1;4 (Nax1) and one inactive HKT1;4 gene. Using these sequences as template for primer design enabled mapping of at least three HKT1;4 genes onto chromosome 2AL in bread wheat, suggesting that bread wheat carries more HKT1;4 gene family members than durum wheat. However, the combined effects of all Na(+) exclusion loci only accounted for 18% of the variation in seedling biomass under salinity stress indicating that there were other mechanisms of salinity tolerance operative at the seedling stage in this population. Na(+) and K(+) accumulation appear under separate genetic control. The molecular markers wmc170 (2A) and cfd080 (6A) are expected to facilitate breeding for salinity tolerance in bread wheat, the latter being associated with seedling vigour.

Effect of waterlogging on the severity of disease caused by Mycosphaerella pinodes in peas (Pisum sativum L.)

The effect of waterlogging on the severity of disease caused by Mycosphaerella pinodes infection in field pea was measured in 2 experiments in the glasshouse. Disease significantly reduced root and shoot growth in both experiments. In a comparison of 2 cultivars with different sensitivities to waterlogging, the severity of disease was lower in the cultivar which was less sensitive to short-term waterlogging. Flooding the roots of plants after infection increased the visual symptoms of disease, but if plants were inoculated with the pathogen after flooding commenced, disease severity was reduced by waterlogging. Inoculation before waterlogging significantly reduced plant dry matter, but there was no reduction in plant growth by disease when inoculation occurred after waterlogging commenced. The results suggest that waterlogging of peas already infected with Mycosphaerella pinodes may result in more severe infection and greater reductions in plant growth, and cultivars more sensitive to waterlogging damage may also suffer greater losses from disease.

Growth of field pea on red-brown earth soils in a year with high rainfall

A study of 4 commercial crops of peas was conducted in the Lower North of South Australia during 1992 to assess the importance of waterlogging on growth and yield. The area chosen for the survey has a high proportion of red-brown earth soils that slake and seal, have poor internal drainage, and are prone to transient waterlogging. Rainfall in the year of the survey was above average, particularly during September and October, and waterlogging and disease were common in pea crops throughout the region. Based on air-filled porosity and soil water tension, waterlogging occurred in each of the survey paddocks. Differences in vegetative growth and grain yields within and between paddocks could be related to the severity of waterlogging. There were differences between the 4 survey paddocks for concentrations of potassium, sodium, iron, and manganese in pea shoots, and these differences appeared to correspond to differences in the severity of waterlogging. Nutrient concentrations were, however, confounded by differences in soil pH and soil fertility. Despite adequate to high levels of available phosphorus (P) in each of the 4 paddocks, concentrations of P in shoots were generally low and, in 2 cases, indicated P deficiency. Phosphorus concentrations were not related to the concentration in the soil or to the severity of waterlogging. In field experiments conducted over 2 seasons (1991, 1992), peas were grown in raised hill plots to promote drainage around the upper root system. The method significantly increased plant establishment in both years, and in 1992, a year of record high rainfall, grain yields from the drained plots were 5-64 times greater than those from undrained plots. In 1991, a year with lower rainfall, drainage improved pod yield by 13%. Observations during the survey suggested that disease was worse in the paddocks that were severely affected by excess water.

Grain yields of field pea (Pisum sativum L.) in South Australia

The grain yield of field pea (Pisum sativum L.) between 1959-60 and 1991-92 was examined in selected Hundreds in important peagrowing regions of South Australia. Over the 33 years, the rates of increase in grain yield have been substantial, ranging from 20 to 48 kg/ha.year. The rate of increase in the State average for the same period was 22 kg/ha. year. The largest rates of increase have occurred mainly in the Hundreds in the higher rainfall areas. Yields have increased irregularly. During the 1960s grain yields rose relatively slowly, but from the mid 1970s to the mid 1980s, large increases occurred. Since then, yields have increased relatively little or, in some Hundreds, declined. With one exception, grain yield was positively and significantly correlated with seasonal (April-October) rainfall in each Hundred, but there were few significant correlations with rainfall in individual months. Yield was often correlated with winter and autumn rainfall but not with spring rainfall. The efficiencies of seasonal water use in the Hundreds ranged from 2.7 to 4.8 kg/ha.mm; these were lower than the maximum values recorded for other winter grain legumes, suggesting that water use efficiencies can improve substantially.

Effects of subsurface drainage, cultivation, and stubble retention on soil porosity and crop growth in a high rainfall area

Wheat, triticale, and rapeseed growth and yield were studied under various tillage (conventional, deep ripping, direct drilling) and stubble-handling (burnt, retained) regimes with and without drainage at Hamilton in south-western Victoria from 1985 to 1987. Grain yield was increased from about 2 to >4 t/ha by drainage in both years; however, effects of other treatments, although significant, were much less. Soil structure (as measured by fractional air-filled porosity at -5 J/kg) deteriorated during winter and recovered during spring and summer. A laboratory experiment showed that this variation in soil structure resulted from saturation per se and redrying. In the field, the decline in porosity was most pronounced with cultivation and the absence of drainage, but overall, the effects of stubble retention and tillage treatments were small. There was a significant positive relationship between yield and porosity on undrained areas, but not where drains were present. Drainage reduced soil structural decline during winter, while stubble retention reduced the decline in porosity in the cultivated-undrained treatment in 1987.

Effect of form and rate of pig manure on the growth, nutrient uptake, and yield of barley (cv. Galleon)

The effect of 2 rates of piggery waste on the growth, nutrient uptake and yield of barley (cv. Galleon) were compared with a fertiliser mixture of superphosphate and urea in the field. The piggery waste was either applied as a slurry (16 kL/ha or 32 kL/ha) or as a solid (0.5 t/ha or 1.5 t/ha). Both the fertiliser mix and the slurry significantly increased the growth and yield of barley while the dried manure failed to improve growth and yield. The effects of treatments on the nutrient concentration in plant tissue throughout the year were small and mainly not significant, while the increases in nitrogen and phosphorus content in the crop reflected the changes in dry matter production. The grain yield responses to fertiliser and to the slurry appeared due to an increase in nitrogen available to the crop rather than to the increase in the supply of phosphorus or other nutrients. The higher rate of the slurry reduced the boron concentration and increased the sodium concentration in the tissue but the concentrations of these elements were not great enough to affect plant growth adversely. However, the increase in sodium concentration following application of the slurry suggests that there may be some risk in the build up of sodium in the soil with the continued use of high rates of slurry, particularly in drier environments. The experiment indicates that the slurry was as effective as fertiliser in eliciting a response and was more effective, in the short term, than the dried form of manure.

Effect of time of sowing on flowering in faba bean (Vicia faba)

Sequential sowings of faba bean (Vicia faba) were conducted to examine the effect of sowing date and a vernalisation treatment on the phenology of a range of faba bean accessions. There was very little difference between accessions in the rate of germination. Delayed sowing increased the time to establishment, but the thermal time from sowing to emergence did not vary greatly. On average 208�C.day was required for emergence and the base temperature for germination was near 0�C for all accessions. The shortest time from emergence to first flower averaged over all sowing dates was 43 days for Accession 286 (range 29-52 days), and the longest was 73 days for Accession 863 (50-96 days). The greatest response to vernalisation occurred when the seed was sown in early autumn (April). When sown in late winter (August), however, there was little response to vernalisation despite the plants being exposed to higher mean temperatures. In that case, long and lengthening days partly overcame the vernalisation requirement of some cultivars. For the range of sowing dates normally expected in dryland crops in southern Australia, there was little effect of vernalisation on the time to flowering and the major controls of development were through responses to temperature and daylength. The range of maturity types in the current breeding program appears sufficient to extend the range of environments in which faba bean is grown.

Effects of nitrogenous fertilizer on the growth, grain yield and grain protein concentration of wheat

The responses of wheat to applications of nitrogenous fertilizer were examined between 1988 and 1990 at 10 sites in South Australia which were considered to be marginally deficient in N. Nitrogen rates ranged from 0 kg N/ha to 150 kg N/ha and the experiments were sown after a range of crops and pastures. Nitrogen often increased early crop vigour and subsequent vegetative growth but significant increases in grain yield occurred at three of the 10 sites only; at the remaining sites there was no significant response or there was a reduction in yield at the highest rates of N. Kernel weights fell and grain protein concentration increased at most sites as the rate of N increased. The total amount of N per kernel was relatively constant across the N treatments at each site and across the 10 sites it varied less than the starch content per kernel. Grain protein concentration therefore was affected more by the amount of starch deposited in the grain than by the total amount of nitrogen. The amount of dry matter remobilized post-anthesis, calculated from changes in dry weight, was high and at the majority of sites was increased with applications of nitrogenous fertilizer. Despite the generally large amount of dry matter remobilized, this appeared to be used inefficiently during grain filling and there was little evidence that it greatly contributed to grain growth and grain protein concentration. The relationship between starch content per kernel and N content per kernel varied between sites: in some cases starch and N were negatively correlated, while in other instances there was a positive correlation or no correlation. The data suggest that high grain protein concentration at high levels of N are not a direct consequence of increased mobilization of dry matter and greater translocation of N to the grain. Dry matter production at anthesis was correlated with the amount of growth after 10 weeks but generally this increased dry matter production was of no benefit to yield. It is concluded that in the medium rainfall areas of the state, there is no advantage to be gained from improved early vigour, except perhaps where poor early growth is due to inadequate management.

A review of factors affecting minimum temperature reached on clear, windless nights

A mathematical model of heat flux in which net flux was assumed to be proportional to the surface temperature was used to examine the effects of important environmental variables on minimum surface temperatures reached during cloudless nights. Variables considered were altitude, atmospheric water content, surface emissivity, soil heat capacity and conductivity, length of night, and initial starting temperature. Final temperatures reached were especially sensitive to changes in soil thermal conductivity and heat capacity. Both these parameters are affected by moisture content (particularly when low), making this the single most important factor affecting the severity of frost. Lower initial starting temperatures and longer nights increase the severity of frosting, as does any decrease in the depth of the atmosphere (as happens with changes in altitude) or reductions in the water content of the atmosphere. Emissivity of the radiating surface is relatively unimportant. Temperature profiles in the soil were similar, but extended to greater depths as heat capacitance declined, whereas lower thermal conductivity resulted in cooler surface temperatures while the decline in temperature did not extend as deep. The model was shown to be an improvement on one in which net flux was assumed to remain constant, and allows for a more instructive sensitivity analysis.

The growth and yield of uniculm and tillered barley over a range of sowing rates

The growth and yield of two lines of uniculm barley, WID-103 and WID-105, were compared over a range of sowing rates (50-400 kg/ha) with the commercial varieties Galleon and Schooner. The experiments were conducted at Strathalbyn, S.A., in 1986, 1987 and 1988 and at the Waite Agricultural Research Institute in 1987. A third tillered variety, Clipper, was included in the comparison in 1988. Over the three years plant populations measured early in the season ranged from 39/m2 to 709/m2, and grain yields from 97 to 41 1 g/m2. Dry matter production at ear emergence increased with greater plant density, and both the tillered varieties and the uniculm lines showed similar responses to higher sowing rates. At maturity, dry matter production of the tillered barleys was greater than or equal to that of the uniculms and the harvest indices (HIs) of the two types were similar. Consequently, grain yields of the tillered types were greater than or equal to the yields of the uniculms. Over the four experiments the tillered varieties had a 6% higher yield. The number of ears/m2 was the yield component most affected by plant density in both the tillered and uniculm barleys. The uniculm lines had more spikelets/ear, but tended to set fewer grains/spikelet and produce smaller kernels. The experiments failed to demonstrate any advantage of the uniculm habit to the grain yield of barley. These results differ from previous experiments that showed that a uniculm line, WID-101, had a higher yield than the tillered variety Clipper. It is suggested that the uniculm habit per se was not the cause of this higher yield, but its higher HI resulted in it outyielding Clipper. Current varieties, however, have HIs similar to the uniculm lines and yield equally to or more than the uniculm barleys examined. To further improve the grain yield of uniculm barley, greater dry matter production is necessary as the HIs of these lines are already high.

The contribution of nitrogen fertiliser to the nitrogen nutrition of rainfed wheat crops in Australia: a review

Very little nitrogen (N) fertiliser is applied to wheat crops in Australia. Currently, about 105 t of N fertiliser (less than 20% of Australia's total consumption) are used annually at an average rate of 2-3 kg Nha. This scant use of N fertiliser over much of the Australian wheat belt N is because the N derived from a legume-dominant pasture ley is thought to provide a wheat crop's N requirement. However, trends in the grain protein content of Australian wheat and some other indices of soil fertility suggest that legume-based pastures have not always been able to supply all the N required for adequate nutrition of the wheat crop and that there has been some occasional need for extra N from applications of fertiliser. Recent declines in the productivity and quality of pastures has further increased the need for supplementary applications of N fertiliser. The increase in grain legume production also has been partly based on the presumption that grain legumes contribute to the N economy of the following wheat crop. Many experiments throughout the wheat belt show a yield advantage of wheat grown after a grain legume, but these rotation trials also show that the level of productivity of the grain legume has little effect on the yield of the following wheat crop. A review of these experiments suggests that grain legumes, directly, contribute little to the N nutrition of a following wheat crop and their benefit may be from the legume acting as a disease break or providing the opportunity to control grassy weeds.

Responses by wheat to lupin, soil amelioration and fertilizer treatments in a solodised solonetz soil

Disruption of the junction of the A-B horizons of a yellow duplex soil did not affect moisture extraction or grain yield of wheat grown in the Southern Wimmera, and it is unlikely that this zone represents a serious impediment to root growth. However, improving soil fertility, either by growing lupins or by placing nitrogen and phosphorus in the A2 horizon, did increase yields. Following lupins in 1983, wheat yield increased from 4.3 to 55 t/ha in 1984,andfrom 3.1 to3.7 t/ha in 1985. This response was greater than that due to deep placement of nitrogen and phosphorus (0.3 t/ha in 1984,0.4 t/ha in 1985), probably because of improved root growth as a result of less root disease. There were consistent responses to foliar applications of copper and interactions with other treatments; the greatest responses occurred in situations of improved nitrogen nutrition.

GABA distribution in a pain-modulating zone of trigeminal subnucleus interpolaris

A recent model for control of spinal and medullary nociceptive neurons (Basbaum and Fields, 1984) incorporates a gamma-aminobutyric acid-ergic (GABA-ergic) cell into this circuitry and indicates that such elements could act as one substrate for presynaptic inhibition of primary afferents. This concept is supported by a variety of pharmacological and electrophysiological studies. We therefore examined the distribution of GABA-ergic activity in trigeminal subnucleus interpolaris (Vi) by focusing on the types of cells, together with dendritic and synaptic profiles, that are immunocytochemically labeled with an antiserum against glutamic acid decarboxylase (GAD). GAD occurred throughout Vi but was most concentrated in the ventrolateral quadrant and interstitial nucleus. It was localized to groups of small neurons with two to three primary dendrites, and within numerous punctate profiles suggestive of synaptic elements. Electron microscopy revealed labeled dendrites, some of which were postsynaptic to scalloped terminals of presumptive primary afferents. Other labeled dendritic elements, which were quite variable in size, engaged both GAD-labeled and unlabeled synapses. Most GAD synapses displayed clear round vesicles and formed contacts with unlabeled perikarya and a variety of dendritic processes. Numerous GAD-positive synapses were also incorporated into axoaxonic clusters, in which the GAD element was presynaptic to scalloped terminals. Others engaged in serial arrays with other unlabeled terminals, which, in turn, were presynaptic to dendrites. Occasionally, GAD synapses formed contacts with GAD-positive dendrites. These data show that GABA is localized to a variety of neuronal elements in ventrolateral Vi and the interstitial nucleus. These occur in spatial arrangements providing an anatomical substrate for postsynaptic modulation of activity in this area. GABA terminals also appear to be involved in a presynaptic inhibitory mechanism, which may, in some instances, affect transmission in primary afferents.

Effect of waterlogging on the grain yield response of wheat to sowing date in south-western Victoria

Two experiments were conducted in 1983 and 1984 in the Hamilton district in south-western Victoria, which examined, in 1983, the interaction of cultivars of different maturity with sowing date and, in 1984, the interaction of soil waterlogging with anthesis date. In the first experiment the grain yield of Isis and Condor were not significantly (P = 0.05) affected when sowing was delayed from 18 April to 13 May despite greater DM yield at anthesis of the April sown crops (44% with Isis and 8 1 % with Condor). Early sowing resulted in early flowering and in Condor 25% fewer grains per ear. When the effect of anthesis date on grain yield was examined in 1984 at a poorly drained site (Hamilton) and a nearby better drained site (Tabor), it was found that early flowering caused yield reductions of 46 and 25%, respectively. The reduced yield at Hamilton was caused by fewer grains per ear and a lower kernel weight. Grain yield was found to be associated with the severity of waterlogging during the 30 days before anthesis. For each 1% decline in the mean air-filled porosity of the surface soil at this time, yield was reduced by 0.29 t/ha (r2 = 0.83; P< 0.05). When the soils became waterlogged, nitrogen concentrations in the plant tops declined to low levels between stem elongation and anthesis. The need to avoid waterlogging damage during stem elongation in spring may necessitate anthesis being delayed beyond the time currently recommended for the district.

The effect of time of sowing on the grain yield of irrigated wheat in the Namoi Valley, New South Wales

The effect of time of sowing on the yield of 15 wheat cultivars grown under irrigation was examined at Narrabri, N.S.W. Sowing dates, which ranged from mid-April to mid-August, encompassed the period of sowing normally found with commercial crops. The length of the pre-anthesis period was affected by both temperature and photoperiod. There was evidence of a vernalization requirement for some of the winter and midseason cultivars, but, overall, photoperiod was the more important environmental factor determining pre-anthesis development. Each day's delay in sowing caused a delay of between 0.48 and 0.75 days in anthesis; the delays observed for spring wheats were generally greater than those reported for dryland wheat in eastern Australia. Winter cultivars generally did not show an optimum sowing or anthesis date. For spring cultivars, the optimum time of sowing was early June (range of about 3 weeks), while the optimum anthesis date was the last week of September (range of 1 week). Grain yields of spring cultivars were reduced by 6 and 16% per week's delay in sowing and anthesis respectively. Despite a non-limiting water supply, yields at late plantings were low, which was largely the result of hastened crop development and high temperatures during grain-filling. The environmental factors which determined the optimum sowing and anthesis dates were the incidence of early spring frosts and high spring temperatures. If frosts were not a factor at Narrabri, the optimum time of flowering would be 6-8 weeks earlier than the present optimum.

Moldy sweetclover poisoning in a horse

A six year old Percheron mare was presented with a history of spontaneous unilateral epistaxis of 24 hours duration. The blood one stage prothrombin and partial thromboplastin times were markedly prolonged. A diagnosis of moldy sweetclover poisoning was made on the basis of the history and clinical and laboratory findings. A single whole blood transfusion and four daily intravenous injections of vitamin K(3) proved to be a successful treatment.