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981.
Osteoporosis, a manifestation of bone atrophy that leads to great susceptibility to fractures, is a very important public
health problem today because of its great morbidity, mortality and important economic repercussions. It is a problem that
will tend to become more serious with the increase in the number of elderly persons. Bone mass is gained during adolescence,
reaches a plateau during the third decade and remains stable until approximately age 50, after which a progressively gradual
loss is observed. There is no real cure for osteoporosis, but a series of strategies can be used to reduce bone loss and improve
bone mass. Osteoporosis has been considered a disease that accompanies the process of ageing; however, this fatalistic attitude
should be discarded, as it is possible to correct and decrease the risk factors. Intervention strategies are based on three
pillars: nutrition, physical activity and pharmacological agents. Physical activities and exercise programmes are important
because they not only can counter the loss of bone mass but also improve neuromuscular capacity, maintaining and increasing
strength and muscle mass, which can help to avoid falls and reduce their impact and consequences. The general principles that
apply to any exercise programme also apply to preventing bone mass loss. They also can be applied to persons with osteoporosis.
However, to understand the peculiarities of these programmes, the propensity for suffering fractures of these former groups
should be kept in mind. Special care should be taken to avoid falls and injuries. Weight-bearing exercise and resistance training
are recommended for the prevention programmes. Other activities such as tai-chi, dancing, gymnastic or callisthenic exercises
can help to improve balance, gait and muscle coordination and diminish the risk of falling. These programmes should be complemented
with postural education and a series of safety precautions. 相似文献
982.
983.
Three-hundred-eleven female drug-using sex workers in urban Puerto Rico were asked to describe their last negotiation with a client. They described efforts to protect themselves from many hazards of sex work, including violence, illness, and drug withdrawal. They also described efforts to minimize the stigma and marginalization of sex work by cultivating relationships with clients, distinguishing between types of clients, and prioritizing their role as mothers. Sex workers adopted alternating gender roles to leverage autonomy and respect from clients. Their narratives suggest that sex workers negotiate a world in which HIV is relative to other risks, and in which sexual practices which are incomprehensible from an HIV-prevention perspective are actually rooted in a local cultural logic. Future HIV prevention efforts should frame condom use and other self-protective acts in terms that build upon sex workers own strategies for understanding their options and modifying their risks. 相似文献
984.
985.
This study's central objective is to determine how several individual, organizational and ergonomic factors influence the relationship between job stress and mental workload for workers in an electronics company. A cross-sectional study was made as a test of hypotheses regarding that relationship. The sample is composed of 95 workers, of both sexes, from the electronics industry in the metropolitan zone of Guadalajara, Jalisco, Mexico. Ergonomic conditions were evaluated with the Ergonomic Evaluation List, stress was evaluated by administering the SWS-Survey to groups of subjects, and mental workload was evaluated with the NASA-TLX Workload Index. Using Cochran's and Mantel-Haenzsel statistics, the odds ratio for each of the independent variables was {e}stimated as a risk factor for job stress, and analysis was later conducted by means of logistic regression for those risks found to be significant. Of the 95 worker participants, 26.3% presented a high level of job stress and 17.9% of the workers were found to present high levels of mental workload. The results show that working hours, mental demand, temporal demand, and frustration when faced with a given task may be considered risk factors for job stress. 相似文献
986.
987.
In this work, we develop statistical inference for the parameters of a discrete-time stochastic SIR epidemic model. We use a Markov chain for describing the dynamic behavior of the epidemic. Specifically, we propose estimators for the contact and removal rates based on the maximum likelihood and martingale methods, and establish their asymptotic distributions. The obtained results are applied in the statistical analysis of the basic reproduction number, a quantity that is useful in establishing vaccination policies. In order to evaluate the population size for which the results are useful, a numerical study is carried out. Finally, a comparison of the maximum likelihood and martingale estimators is conducted by means of Monte Carlo simulations. 相似文献
988.
A recent investigation of the British General Household Survey (GHS) found substantial over-reporting of childlessness in recent years, particularly at older ages. We examine the phenomenon in further detail and find that the principal cause was change in survey procedures. To some extent the bias can be corrected for by using information on own children in the household. Revised fertility histories give period estimates of total fertility that are in close agreement with national vital registration statistics, unlike those based on original fertility histories of recent years. Misreporting in fertility histories dates primarily from administrative changes in the GHS in the years 1998-2000, and particularly from 2003, when the option of laptop self-completion (CASI) was introduced for reporting demographic histories. 相似文献
989.
Mª del Mar Salinas-Jiménez Joaquín Artés Javier Salinas-Jiménez 《Social indicators research》2011,103(3):409-426
In this paper we empirically investigate the direct effects of education on utility. Besides investment aspects of education,
the focus is placed on its consumption component and on education positional concerns. We use data from the World Values Survey
(WVS) and adopt a life satisfaction approach. First, we find that education shows a significant effect on life satisfaction
independent of its effect on income, thus identifying a consumption component of education. Furthermore, given that the contribution
of education to individual wellbeing might depend partly on relative position rather than absolute levels, we next study whether
education can be considered as a positional good. To this end we analyse the relationship between education and life satisfaction
for people in different income groups in which the reference levels of education may differ. Additionally, we control for
occupational status since benefits from education could appear via occupational benefits. Our results indicate that the contribution
of education to subjective wellbeing is stronger as less people attain a given level of education, thus suggesting that this
contribution is partly due to positional concerns. 相似文献
990.
The purpose of this study was to evaluate the effect of residual variability and carryover on average bioequivalence (ABE) studies performed under a 22 crossover design. ABE is usually assessed by means of the confidence interval inclusion principle. Here, the interval under consideration was the standard 'shortest' interval, which is the mainstream approach in practice. The evaluation was performed by means of a simulation study under different combinations of carryover and residual variability besides of formulation effect and sample size. The evaluation was made in terms of percentage of ABE declaration, coverage and interval precision. As is well known, high levels of variability distort the ABE procedures, particularly its type II error control (i.e. high variabilities make difficult to declare bioequivalence when it holds). The effect of carryover is modulated by variability and is especially disturbing for the type I error control. In the presence of carryover, the risk of erroneously declaring bioequivalence may become high, especially for low variabilities and large sample sizes. We end up with some hints concerning the controversy about pretesting for carryover before performing ABE analysis. 相似文献