The effects of sex steroids and some elements of lifestyle on the normal variation of bone mineral content in younger versus older healthy Polish males

The aim of the study was to evaluate the independent ‘net’ effects of hormonal variables (estradiol, free testosterone and dehydroepiandrosterone sulfate (DHEAS) levels) and lifestyle variables (alcohol consumption, coffee drinking, cigarette smoking, physical activity and muscle strength) on trabecular, cortical and total bone mineral content (BMC) in a group of 236 healthy males, aged 22–67 years. The men were occupationally active inhabitants of the city of Wroclaw, Lower Silesia, Poland. Trabecular, cortical and total bone mineral content, at the distal radius of the non-dominant hand, were assessed by peripheral quantitative computed tomography (pQCT) using the Stratec 960 apparatus. Sex steroids levels were measured using standard immunoassays. Data on lifestyle variables (alcohol consumption, cigarette smoking, coffee drinking and physical activity) were obtained through a questionnaire. Hand-grip strength of the dominant hand was assessed using a standard dynamometer. All statistical analyses were made separately in two subgroups, younger males (aged 22–39 years) and older males (aged 40 years and over). The impact of a particular independent variable on BMC and the extent of determination on BMC by the complex of chosen variables were evaluated using a path analysis. In younger males, the effects of physical activity and muscle strength were the most important among all the factors that influenced BMC, as they contributed to 16.2%, 16.9% and 16.5% of the variability of trabecular, cortical and total BMC, respectively. Taking into consideration cigarette smoking, alcohol and coffee drinking together, the coefficients of determination of the variability in trabecular, cortical and total BMC were 10.6%, 11.3% and 16.1%, respectively. The variances in trabecular, cortical and total BMC levels were determined in only 5.8%, 11.5% and 13.0% by sex steroids, respectively. The influence of free testosterone on trabecular BMC was greater compared with that of dehydroepiandrosterone sulfate (DHEAS) and estradiol; for cortical BMC, the impacts of estradiol and DHEAS were similar and greater than that of free testosterone, and the variability of total BMC was affected mainly by estradiol. In contrast, in older men the effects of physical activity and muscular strength were the least important among all the complexes of independent variables, as they contributed to 4.5%, 7.8% and 7.0% of the variability in trabecular, cortical and total BMC, respectively. Taking into consideration the influences of cigarette smoking, alcohol and coffee drinking, the coefficients of determination of the variability in trabecular, cortical and total BMC were 16.5%, 14.8% and 17.4%, respectively. Among the older men, the variances in trabecular, cortical and total BMC were determined in only 9.4%, 6.3% and 13.6% by sex steroid levels, respectively. The influence of DHEAS on trabecular BMC was greater when compared with that of estradiol and free testosterone, whereas the variability of both cortical and total BMC in older men was affected mainly by estradiol. It is quite striking that, in younger healthy subjects, both physical activity and muscle strength contributed to a greater extent to BMC variance when compared with sex steroids levels, whereas, in older men, physical activity and muscular strength were less important than androgen- estrogen activity in determining the variability of BMC. This may suggest that the tropic effect of mechanical force influences bone structure mainly in younger men; probably male bone tissue becomes less prone to mechanical stimuli during aging. It is astonishing that both in younger and older men the coefficients of determination of physical activity and muscle strength were the highest for cortical BMC, which would indicate the greatest response of that part of the bone tissue to mechanical force. It is worth noting that the coefficients of determination of the complex of lifestyle factors (alcohol consumption, cigarette smoking and coffee drinking) were higher in older men compared to younger Polish males. This can be explained by the longer exposure of male bone to environmental influences (ethanol, nicotine, caffeine) during a lifetime. Our study revealed that all the evaluated variables were related to the variability in BMC in healthy Polish men, but the coefficients of determination differed depending on the age of the examined subject and on the BMC of a particular bone component. This suggests that the responsiveness of male bone tissue to environmental factors changes with age, and that these effects vary significantly between particular parts of the male bone structure.     

社会转型时期乡村人口流动与乡村安全研究

改革开放以来,我国出现了以农村青壮年劳动力为主导的大规模人口流动,它已成为我国转型社会的一个显著特征。农村青壮年人口的外流使得农村人口处在不断地流动之中,如此持续性和季节性的流动给乡村安全带来了巨大的影响。具体表现在乡村生产安全、乡村生活安全、乡村教育安全、乡村治安等方面,而安全问题的化解需要从政府、乡村组织及个体等层面的合作寻求突破。     

Using population screening for recruitment of young adults engaged in illicit drug use: Methodological issues and sampling outcomes

Social stigma, legal sanctions and the associated lack of sampling frames create barriers to the probabilistic sampling of those engaged in a variety of behaviour, including illicit drug use. We used a novel sampling approach to recruit respondents into a longitudinal study examining amphetamine-type stimulant use. A young adult population was screened for lifetime drug use to create a sampling frame of amphetamine-type stimulant users and non-users. We posted 12,118 screening questionnaires to a random selection of young adults listed on the electoral roll for Brisbane and the Gold Coast, Australia (N = 107,275). Using a small pre-paid incentive and intensive telephone and postal reminders we attained a screening response rate of 49.9%. Eligible amphetamine-type stimulant users (used ecstasy or methamphetamine ⩾ 3 times in past 12 months) and non-users (never used ecstasy or methamphetamine) were identified by screening responses. About two-thirds of each selected group took part in the longitudinal study. Comparisons with large-scale population survey data suggest the sample was broadly representative of young adult amphetamine-type stimulant users in Australia.     

中国人口老龄化区域差异与收敛性研究

本文通过对中国人口老龄化空间分布特征的分析，得出各地区人口老龄化程度普遍加深且存在空间聚集性，呈现东部沿海－中部－西部内陆的扩张规律，形成了沿长江流域严重老龄化聚集地带。此外，全局和局部 Moran 指数显示我国人口老龄化存在显著的全局和局部空间正相关关系。于是考虑空间相关性，借鉴经济增长收敛性的研究方法，建立空间计量模型，发现我国地区间人口老龄化存在绝对β收敛，且收敛速度较快。     

论新疆少数民族人口发展和生育观的新变化

随着新疆跨越式的发展,政府政策、社会经济、就业等因素使少数民族人口和生育观有了新的变化。为了适应新的变化,推动少数民族人口生育与社会经济协调发展,文章对新疆少数民族生育观念发生转变的影响因素进行分析和总结,认为只有坚持过去的成功经验,不断开拓创新,提高少数民族人口素质,加强人口的文化素质培育,加快新疆城市化建设,才能实现新疆人口、社会、经济的科学发展目标。     

不同户口类型流动人口城市生存状态的差异

基于2009年福建省一项问卷调查数据,从就业收入、社会保险、子女教育、居住和社会融合五个方面考察了流动人口中不同类型户口持有者的城市生存状况。结果表明,在上述五方面,流动人口的城市生存状况存在明显差别,而这些差别的产生仍与户口性质密切相关。     

流动劳动力的人力资本与就业身份选择——基于东部和中西部地区在京就业者的比较

利用2006年＂北京市1‰流动人口调查＂数据,分别考察来自东部和中西部地区的在京流动劳动力的就业身份构成,并运用Logistic回归法分析人力资本对流动劳动力不同就业身份选择的影响及作用机制。研究发现,流动劳动力的人力资本提升对改善其就业身份有显著正面影响;受教育年限和健康状况对中西部地区流动劳动力更为重要,对流动劳动力成为雇主的正向影响明显高于来自东部地区者。据此认为,在提升劳动力人力资本之外,针对流动劳动力的系统性边缘化制度安排需要打破。     

“十二五”期间贵州农村三类劳动力规模估算

农村人口流动必然会引致三类群体产生：外出农民、返乡农民和留守农民群体。使用1996—2009年贵州省统计资料,通过线性模型、时间序列模型等方法,对这三类农民群体＂十二五＂期间规模的预测表明：期间留守农民人数将缓慢减少;外出农民和返乡农民人数则不同程度地增加;到＂十二五＂期末,即2015年时,三类群体规模分别将达1 162.75万人、749.42万人和62.74万人。     

Types and timing of child maltreatment and early school success: A population-based investigation

The purpose of the present study was to investigate the prevalence of types of child maltreatment and co-occurring risks in an entire county population of children in public education and to examine the unique relations of the child maltreatment types and timing on children's early academic success while accounting for the children's multiple-risk context. A cohort of 11,835 second grade students who were born in the county and attended the public school district served as participants. Information on first reported experiences of substantiated physical abuse, neglect, unsubstantiated child maltreatment reports, health, maternal, and social risks, and academic and behavioral outcomes was obtained and linked through a county-wide integrated data system. Results indicated that after controlling for demographics and the set of other risks, substantiated child neglect and unsubstantiated reports were associated with poorer outcomes than physical abuse. Also, first substantiated child maltreatment and unsubstantiated reports prior to kindergarten were related to a more comprehensive set of poor outcomes than post-kindergarten first reports. The differential patterns that emerged for the association between age of first reported maltreatment by type and educational outcomes were discussed with implications for future research and policy.     

人口老龄化对福建省城镇职工养老保险制度的影响及政策建议

福建省持续加重的人口老龄化趋势对城镇职工养老保险制度产生了影响。研究发现:在将来一段时期内,福建省城镇职工社会养老保险基金收入及支出都将呈现快速增长趋势,但支出会大于收入;社会养老保险基金在经过一段时期的平衡后,会出现一定缺口。可以在以下几个方面对城镇职工社会养老保险制度进行完善:扩大城镇职工社会养老保险制度的覆盖面;依法做好养老保险费的征缴工作;将城镇职工社会养老保险基金统筹级次提高到省级层面;推进养老保险基金信息管理系统建设等。