The Aging Farm Population and Rural Aging Research

ABSTRACT

This article explores the potential and the promise of convergence between gerontological and occupational health researchers to better understand challenges faced by aging farmers including declining economic viability of family farms, the aging of the population of working farmers, and probability of work-related injury or disability among older farmers. Although the need for research seems obvious, the economic, demographic, and psychosocial dynamics of continued work among aging farmers is under-studied in the occupational health literature and absent in the gerontological literature. Following examination of studies of aging farmers drawn from the occupational health literature, we review studies of rural aging in the gerontological literature. First, we compare varying definitions of rural across federal agencies that impact the ability of researchers using these data to examine variability across rural places. Next, we review studies based upon primary data that include rural residence among their independent variables. We describe different definitions of rural residence across federal agencies with an eye toward their methodological and conceptual impact on the rural aging literature. Then we describe inadequate and incomplete definition and measurement of rural residence across published studies of primary data. Following discussion of the implications of these shortcomings for rural aging research including farmers and others engaged in extractive activities, we discuss the potential for joint work among gerontologists and occupational health researchers to better understand the significance of aging for transition in the agricultural economy and the viability of family farms. We recommend attention to the definition and measurement of rural residence to include variability in rural farm and non-farm populations and refocusing the occupational health literature on aging farmers to include a life course perspective from gerontological theory applied through longitudinal research designs.     

Aging muscle

Age causes structural and functional changes in skeletal muscle in a wide range of species, including humans. Muscle changes in humans start in the fourth decade of life and cause frailty and disabilities. Associated changes in body composition form the basis of many metabolic disorders, such as insulin resistance, type 2 diabetes, hypertension, and hyperlipidemia, which result in an increased incidence of cardiovascular death. Decreases in the synthesis rates of many muscle proteins, specifically of myosin heavy chain and mitochondrial proteins, occur with age. The underlying causes of the reduction in mitochondrial biogenesis and ATP production seem to be decreases in mitochondrial DNA and messenger RNA. Reduced ATP production could be the basis of reduced muscle protein turnover, which requires energy. Both aerobic exercise and resistance exercise enhance muscle protein synthesis and mitochondrial biogenesis. Insulin and amino acids have also been shown to enhance muscle mitochondrial biogenesis and mitochondrial protein synthesis. However, the insulin-induced increase in muscle mitochondrial ATP production is defective in type 2 diabetic patients with insulin resistance. Moreover, a dissociation between increases in muscle mitochondrial biogenesis and insulin sensitivity after exercise has been noted in older persons. It remains to be determined whether muscle mitochondrial dysfunction causes or results from insulin resistance. Exercise seems to enhance the efficiency of muscle mitochondrial DNA in rodents. Reduced physical activity as a contributor of age-related mitochondrial dysfunction remains to be determined. It is proposed that a reduction in tissue mitochondrial ATP production signals the hypothalamic centers to reduce spontaneous physical activities. Voluntary physical activity is regulated by cognitive centers and could attenuate the progressive decline in mitochondrial functions that occurs with age.     

卵巢衰老

女性卵巢衰老的发生远远提前于其身体其他器官的衰老,且现代社会越来越多的女性推迟生育年龄,使卵巢衰老问题受到广泛的关注.首先介绍卵巢衰老的主要表现:即卵子数量的减少、卵子质量的下降以及卵巢相关激素水平的变化.而后概述近年来卵巢衰老内在机制的研究,包括:活性代谢产物[活性氧簇(ROS)、活性碳簇(RCS)]的积累、基因组DNA和线粒体DNA的突变、端粒长度缩短和端粒酶活性的下降.近年来,关于延缓卵巢衰老的研究发现,抗氧化剂和热量限制可以延缓卵巢衰老甚至延长动物寿命.     

卵巢衰老

女性卵巢衰老的发生远远提前于其身体其他器官的衰老,且现代社会越来越多的女性推迟生育年龄,使卵巢衰老问题受到广泛的关注.首先介绍卵巢衰老的主要表现：即卵子数量的减少、卵子质量的下降以及卵巢相关激素水平的变化.而后概述近年来卵巢衰老内在机制的研究,包括：活性代谢产物[活性氧簇（ROS）、活性碳簇（RCS）]的积累、基因组DNA和线粒体DNA的突变、端粒长度缩短和端粒酶活性的下降.近年来,关于延缓卵巢衰老的研究发现,抗氧化剂和热量限制可以延缓卵巢衰老甚至延长动物寿命.     

Diabetes and Aging

If conventional criteria for glucose tolerance testing are applied uncritically, the majority of the nation's elderly fall within the “diabetes” range. Dr. Andres notes that these standards were developed for the most part from data obtained in studies of young adults. An age effect must be taken into consideration, and a method is proposed for doing so.     

Aging and Survival

The aim of this thesis was to explore the influence of social, biobehavioural, and genetic factors on survival in old age.

Three large databases comprising Swedish elderly were analysed. Study I was performed on a nationwide random sample originally collected in 1954 by Statistics Sweden for a government commission on elderly affairs. It comprised non-institutionalised persons, 67 years and older. Study II and Study III were based on data prospective longitudinal population study of elderly in Göteborg, the H70-investigation. The analyses were performed mainly on a random sample of 70-year-old persons, which was compiled in 1971/1972. In Study IV, data on centenarians were collected from official publications from Statistics Sweden. Data oldest part of the Swedish Twin Registry was used in Study V. This registry was compiled in 1961 and includes like sexed twins born between 1886 and 1925 of which 10,505 twin pairs were included.

The common objective for all studies in this thesis is survival, expressed as length of life or as age at death.

The results show that there is no single factor nor is there a specific set of factors that can be identified as the best predictor of survival. Related variables can be systematised into higher level domains. As an alternative to the use of a set of specific variables for predicting survival/death, a number of risk domains can be utilised. Survival capacity is dependent on the shared influence of factors from various domains like health, cognition, mobility, lifestyle, activities, social networks, etc. Deficits in one domain can be compensated by great capacities in other domains. A good predictor of survival reflects the effects of a complex network of factors. A measure of lung capacity proved to possess this quality and was the single best variable to predict survival among all those variables included in these studies.

Among the centenarians an increased mortality rate was observed during the winter season. At these high ages the level of vigour is low and minor environmental stress will be enough to cause death.

The twin studies showed that about one third of the variance of longevity can be explained by genetic effects, and two thirds of the variance are due to environmental effects. The genetic effect seems to diminish in importance in old ages.     

Sarcopenia and Aging

Sarcopenia refers to the gradual decline in muscle mass and quality noted with advancing age. There is growing evidence linking sarcopenia to functional disability, falls, decreased bone density, glucose intolerance, and decreased heat and cold tolerance in older adults. Factors implicated in the etiology of sarcopenia include decreased physical activity, malnutrition, increased cytokine activity, oxidative stress, and abnormalities in growth hormone and sex steroid axes. At present, progressive resistance training is the best intervention shown to slow down or reverse this condition. Preliminary studies show that the utilization of several trophic factors, notably testosterone and DHEA, may have a salutary effect on muscle mass and/or strength in older adults. More research is needed, however, before drawing definite conclusion as to the clinical utility of these substances in the management of sarcopenia.