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Mental stress is associated with higher mortality, but it remains controversial whether the association is causal or a consequence of a higher physical disease burden in those with a high mental stress load. Understanding causality is important when developing targeted interventions. We aimed to estimate the effect of mental stress on mortality by performing a ‘natural’ experiment using spousal bereavement as a disease-independent mental stressor.
We followed a population-based matched cohort, including all individuals in Denmark bereaved in 1997–2014, for 17 years. Prospectively recorded register data were obtained for civil and vital status, 39 mental and physical diagnoses, and socioeconomic factors.
In total, 389 316 bereaved individuals were identified and 137 247 died during follow-up. Bereaved individuals had higher all-cause mortality than non-bereaved references in the entire study period. The relative mortality in the bereaved individuals was highest shortly after the loss (adjusted hazard ratio (aHR), first month: 2.50, 95% confidence interval (CI) 2.37–2.63; aHR, 6–12 months: 1.38, 95% CI 1.34–1.42). The excess mortality rate associated with bereavement rose with increasing number of physical diseases (1.33 v. 7.00 excess death per 1000 person-months for individuals with 0 v. ⩾3 physical conditions during the first month) and was exacerbated by the presence of mental illness. The excess mortality among bereaved individuals was primarily due to death from natural causes.
Bereavement was associated with increased short-term and long-term mortality, even after adjustment for morbidities, which suggests that mental stress may play a causal role in excess mortality.
A fire-mediated recruitment bottleneck provides a possible explanation for the coexistence of trees and grasses in mesic savannas. The key element of this hypothesis is that saplings are particularly vulnerable to fire because they are small enough to be top-killed by grass fires, but unlike juveniles, they take several years to recover their original size. This limits the number of recruits into the adult size classes. Thus savanna vegetation may be maintained by a feedback whereby fire restricts the density of adult trees and allows a grass layer to develop, which provides fuel for subsequent fires. Here, we use results from a landscape-scale fire experiment in tropical Australia, to explore the possible existence of a recruitment bottleneck. This experiment compared tree recruitment and survival over 4 y under regimes of no fire, annual early and annual late dry-season fire. Stem mortality decreased with increasing stem height in the fire treatments but not in the unburnt treatment. Tree recruitment was 76–84% lower in the fire treatments than the unburnt treatment. Such fire-induced stem loss of saplings and reduced recruitment to the canopy layer in this eucalypt savanna are consistent with the predictions of the fire-mediated recruitment bottleneck hypothesis.
We describe aspects of the life history of Erynnis propertius (Scudder and Burgess) (Lepidoptera: Hesperiidae) by examining several populations over multiple years. We focused on peripheral populations of this species because they are isolated, are threatened by habitat loss, and may play an important role in driving poleward range expansion under increasing regional temperature. Our findings show that the annual larval growth rate does not vary directly with temperature, adult flight phenology and the timing of key resources respond to average daytime temperatures in spring, and population-density patterns among sites are robust over years across a broad region near the species' northern range limit. In addition, we provide descriptions of all larval instars for this species. This fundamental information about the biology, timing, and abundance of this species will facilitate further experimental study and improved assessment of its conservation status.
The Macarthur-Bates Communicative Development Inventories (CDI) have been used widely to document early communicative development. The paper reports on a large community sample of 1,447 children recruited from low, middle and high socioeconomic (SES) areas across metropolitan Melbourne, Australia. Regression analyses were conducted to determine the extent to which communicative behaviours reported at 0 ; 8 and 1 ; 0 predicted vocabulary development at 1 ; 0 and 2 ; 0. In support of previous findings with smaller, often less representative samples, gesture and object use at 1 ; 0 were better predictors of 2 ; 0 vocabulary than were gesture and object use at 0 ; 8. At 1 ; 0, children from the lower SES groups were reported to understand more words than children from the higher SES groups, but there were no SES differences for words produced at 1 ; 0 or 2 ; 0. The findings add to our understanding of the variability in the development of early communicative behaviours.
The origin and course of the carotid arterial sysem in the superior mediastinum and neck are remarkably constant. Although variations are rare, they can have important implications in certain clinical problems. In this report, a patient underwent free jejunal graft repair of a cervical oesophageal stricture caused by radiotherapy for a post-cricoid carcinoma. The common carotid artery on the side of the surgical approach was found to cross the midline to the other side of the neck, and created difficulties both with the procedure and future management. This has not been previously reported.
Radiocarbon analyses by accelerator mass spectrometric (AMS) techniques on organic fractions of human bone from various North American localities previously assigned ages ranging from about 70,000 to 15,000 years B.P. now suggest that none of these skeletons is older than 11,000 C-14 years B.P.
Atoll-dwelling people of Tokelau in the central Pacific have been studied in their home environment and after migration to the industrial culture of New Zealand (NZ). The NZ migrants reflect the predominantly male and young composition of the migrating group. Recent migration has eased the lot of the surplus young women from Tokelau, resulting in earlier marriage and less long-term spinsterhood. The apparently higher fertility of women residing in NZ is largely explained by selection of female migrants who already have two or more children. Earlier menarche and earlier marriage in NZ probably contribute little. Future trends will be monitored, and a decline in migrant fertility is expected, if Tokelauans follow the pattern of other Polynesian migrants to urban environments.
The Tokelau Island Migrant Study is outlined. It is a multi-disciplinary study of health and social change in the Tokelau islanders, following up emigrants to New Zealand (NZ). In this paper fertility and related aspects are examined, comparing pre-migrants (persons subsequently known to have emigrated to NZ) with non-migrants. Pre-migrant females tended to be younger, to marry later, to be less often childless and to have suffered more miscarriages, than non-migrants. Tokelau parity lagged behind other Polynesian populations due to later marriages, and reached a level below that of the more westernized Rarotongans and NZ Maoris.
Tokelau life expectancy was estimated to be 62·2–62·6 years for males and 62·9–66·4 years for females.
Using Persian Blackhead ewes, milk composition and the effect of diet on content of milk fat and milk yield were investigated. Analysis of the milk of nine ewes for fat, protein, ash and lactose (by difference) throughout a twelve-week lactation gave results which were compared with those in the literature. Average values were 5·9, 5·6, 1·0 and 4·8 % respectively. The milk of nine ewes fed on a high plane of nutrition contained significantly more fat than that of ewes fed on a low plane of nutrition; values were 8·8 and 8·3 % respectively. High plane ewes gave significantly more milk than low plane ewes. Ewes suckling twins gave significantly more milk than those suckling singles. Lambs suckling high plane ewes gained significantly more weight than those suckling low plane ewes both from birth to 3 weeks as well as from birth to 12 weeks. Male lambs gained significantly more weight than females.
Highly significant correlation coefficients were obtained between milk consumed by the lamb and its gain in weight. Conversion efficiencies of milk to gain in weight were calculated and compared with literature values.
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