			Home About us Contact

Optimal Age (optimal + age)

Distribution by Scientific Domains

Medical Sciences	57%
Life Sciences	28%

Selected Abstracts

REVIEW OF THE EXTENT TO WHICH ORCHIDOPEXY IS PERFORMED AT THE OPTIMAL AGE: IMPLICATIONS FOR HEALTH SERVICES

ANZ JOURNAL OF SURGERY, Issue 11 2008
Christine J. P. Bruijnen
Background: In recent decades, the recommended age for orchidopexy for primary undescended testes has decreased, in the expectation that this might improve subsequent fertility. The aim of this study was to investigate whether this is reflected in a reduction in the age at which orchidopexies are carried out, and the implications for child health services. Methods: All boys who underwent an orchidopexy for an undescended testis carried out by the Christchurch-based paediatric surgical service between January 1997 and December 2007 were identified through a prospectively collected database. They were analysed according to the age at time of operation and year of surgery to determine whether there was any trend over time. The proportions of children younger than 2 years and between 2 and 5 years of age were calculated for each year. Results: In total, 788 boys underwent orchidopexies for primary undescended testes, with 335 (42.5%) boys having surgery before the age of 2 (mean age 54.3 months, median 31.1 months). During the whole 11-year period, there was no significant change in age at orchidopexy, whereas from 2003, a significant trend towards lower age at operation (Spearman's rank ,0.1112, P = 0.0071) and a significant increase in the proportion of boys having surgery before the age of 2 (Spearman's rank 0.9000, P = 0.0374) were seen. Conclusions: Although there has been a modest reduction in the mean age of orchidopexy since 2003, overall, the mean age at orchidopexy remains well above the recommended optimal age, implying that more attention should be paid towards earlier diagnosis and referral for primary undescended testes. [source]

An evolutionary ecological perspective on demographic transitions: Modeling multiple currencies

AMERICAN JOURNAL OF HUMAN BIOLOGY, Issue 2 2002
Bobbi S. Low
Life history theory postulates tradeoffs of current versus future reproduction; today women face evolutionarily novel versions of these tradeoffs. Optimal age at first birth is the result of tradeoffs in fertility and mortality; ceteris paribus, early reproduction is advantageous. Yet modern women in developed nations experience relatively late first births; they appear to be trading off socioeconomic status and the paths to raised SES, education and work, against early fertility. Here, [1] using delineating parameter values drawn from data in the literature, we model these tradeoffs to determine how much socioeconomic advantage will compensate for delayed first births and lower lifetime fertility; and [2] we examine the effects of work and education on women's lifetime and age-specific fertility using data from seven cohorts in the Panel Study of Income Dynamics (PSID). Am. J. Hum. Biol. 14:149,167, 2002. © 2002 Wiley-Liss, Inc. [source]

Survival of stocked Atlantic salmon and coarse fish and an evaluation of costs

FISHERIES MANAGEMENT & ECOLOGY, Issue 3-4 2004
M. W. Aprahamian
Abstract The stocking of fish represents a major activity in current fisheries management practice. To maximise benefit to the environment in general and to fisheries in particular, optimal stocking strategies need to be developed. Examples from two studies, one involving Atlantic salmon, Salmo salar L., and the other involving three coarse fish species, are used to illustrate how such strategies might be developed. Atlantic salmon fed fry (age 0+) were stocked into eight streams in the North West of England at densities ranging from 1 to 4 m,2 over a period of up to 3 years to evaluate survival to the end of the first and second growing periods. Survival to the end of the first growing period (mean duration 108 days) varied between 1.2 and 41.3% with a mean of 20.45% and CV of 0.53. Survival from the end of the first growing period to the end of the second growing period (mean duration 384 days) ranged from 19.9 to 34.1% with a mean of 26.3% and a CV of 0.21. Hatchery-reared roach, Rutilus rutilus (L.), chub, Leuciscus cephalus (L.) and dace, Leuciscus leuciscus (L.), were stocked into four rivers to determine the optimal age and season which would maximise survival over a 6-month post-stocking period. Post-stocking persistence within the stocked reaches was generally low; the highest level of persistence was estimated at only 33.8%. However, most of the estimates of persistence were considerably lower and (in practical terms) approached zero in several instances. The analysis indicated that river-specific factors are important in determining the success of stocking exercises. The survival estimates derived from these two studies were compared with other published estimates. [source]

The importance of growth and mortality costs in the evolution of the optimal life history

JOURNAL OF EVOLUTIONARY BIOLOGY, Issue 6 2006
D. A. ROFF
Abstract A central assumption of life history theory is that the evolution of the component traits is determined in part by trade-offs between these traits. Whereas the existence of such trade-offs has been well demonstrated, the relative importance of these remains unclear. In this paper we use optimality theory to test the hypothesis that the trade-off between present and future fecundity induced by the costs of continued growth is a sufficient explanation for the optimal age at first reproduction, ,, and the optimal allocation to reproduction, G, in 38 populations of perch and Arctic char. This hypothesis is rejected for both traits and we conclude that this trade-off, by itself, is an insufficient explanation for the observed values of , and G. Similarly, a fitness function that assumes a mortality cost to reproduction but no growth cost cannot account for the observed values of ,. In contrast, under the assumption that fitness is maximized, the observed life histories can be accounted for by the joint action of trade-offs between growth and reproductive allocation and between mortality and reproductive allocation (Individual Juvenile Mortality model). Although the ability of the growth/mortality model to fit the data does not prove that this is the mechanism driving the evolution of the optimal age at first reproduction and allocation to reproduction, the fit does demonstrate that the hypothesis is consistent with the data and hence cannot at this time be rejected. We also examine two simpler versions of this model, one in which adult mortality is a constant proportion of juvenile mortality [Proportional Juvenile Mortality (PJM) model] and one in which the proportionality is constant within but not necessarily between species [Specific Juvenile Mortality (SSJM) model]. We find that the PJM model is unacceptable but that the SSJM model produces fits suggesting that, within the two species studied, juvenile mortality is proportional to adult mortality but the value differs between the two species. [source]

REVIEW OF THE EXTENT TO WHICH ORCHIDOPEXY IS PERFORMED AT THE OPTIMAL AGE: IMPLICATIONS FOR HEALTH SERVICES

Medullary thyroid carcinoma as part of a multiple endocrine neoplasia type 2B syndrome

CANCER, Issue 1 2002
Influence of the stage on the clinical course
Abstract BACKGROUND Multiple endocrine neoplasia type 2B (MEN 2B) is an exceptional syndrome, for which the optimal age of thyroidectomy is poorly established and the course of medullary thyroid carcinoma (MTC) is ill-defined. PATIENTS All the 18 patients with a MEN 2B syndrome examined at the Institut Gustave Roussy were included in a single-center retrospective study. RESULTS There were 9 men and 9 women with a mean age of 13 years (range, 2,27 years) at diagnosis. The diagnosis of MTC was based on the presence of a thyroid nodule or involved neck lymph nodes and on dysmorphic features of MEN 2B in 60% and 40% of the cases, respectively. The classic M918T mutation in exon 16 was found in the 16 patients in whom it was investigated. At diagnosis, 2 patients had Stage I MTC, 15 patients had Stage III, and 1 patient had Stage IV disease. T1 MTC was found in 4 patients aged 2.1,3.7 years. However, two of these patients already had N1 disease. One patient with Stage I MTC, aged 3.4 years and 2 patients with Stage III disease, aged 14 and 25 years, had undetectable basal calcitonin (CT) after initial surgery. During follow-up, basal CT became detectable in one of three patients. Among the 15 other patients with an elevated postoperative CT level, metastases were demonstrated in 5 patients after a mean follow-up of 2 years. Five patients died, three of MTC, one of the MEN 2B syndrome, and one of intercurrent disease. Five- and 10-year overall survival rates were 85% and 75%, respectively. CONCLUSIONS This study confirms the need for early treatment of MTC in patients with the MEN 2B syndrome, preferably within the first 6 months of life. The phenotype of MTC occurring in the MEN 2B syndrome was not more aggressive than sporadic MTC or MTC occurring in other familial syndromes. Cancer 2002;94:44,50. © 2002 American Cancer Society. [source]

Blepharophimosis: a recommendation for early surgery in patients with severe ptosis

CLINICAL & EXPERIMENTAL OPHTHALMOLOGY, Issue 2 2003
Peter S Beckingsale MB BS
Abstract Purpose:,To determine the optimal age for surgical correction of blepharophimosis. Associated features and their effects on incidence of amblyopia were also investigated. Methods:,The study was a retrospective case series of 28 patients with blepharophimosis, ptosis and epicanthus inversus syndrome presenting to a tertiary referral eyelid, lacrimal and orbital clinic. Results:,Amblyopia was present in 39% of patients. Patients with coexistent strabismus had a 64% incidence of amblyopia compared to 24% for those without strabismus. Hypermetropia was present in 43% of patients and 7% were myopic. Significant astigmatism was found in 40% of patients, but these factors did not increase the risk of amblyopia. Patients with severe ptosis had lower rates of amblyopia than those with moderate ptosis but had their ptosis corrected at a median age of 2 years compared to 5 years for those with moderate ptosis. There was an 18% incidence of nasolacrimal drainage problems. A good to excellent cosmetic outcome was achieved in 86% of patients. A positive family history was noted in 75% of patients, usually with paternal inheritance. Conclusions:,Patients with blepharophimosis have a high rate of amblyopia. Co-existent strabismus doubles the risk of amblyopia. Ptosis alone causes mild to moderate amblyopia only. Patients with severe ptosis should have their ptosis corrected before 3 years of age, and all other patients should undergo surgery before 5 years of age. [source]