In most developed Western societies two long-term socio-demographic trends are becoming gradually more visible: First, the birth rate is below that which is necessary to retain a sustainable population. Second, individual life expectancy is steadily increasing due to improvements in medical science and health care. Even though the speed and course of demographic change, and social and economic contexts may vary throughout different parts of the world, the aging of the population has already become a global trend in many Western societies that will gradually have profound impact upon the life circumstances of many individuals . Thus, governments will have to find culturally and ethically sustainable ways to deal with an aging and shrinking population and the economic consequences.
According to the Congressional Research Service Report the birth rate in the United States of America fell significantly from 1957 to 2003 . Although the forecasted socio-demographic change is considerable in the United States, it is supposed to be even more severe in other parts of the world. In particular, Europe must deal with the consequences of a massively growing populus of elderly people in the near future . The difference between the United States and Europe as regards this sociodemographic situation can - at least to some degree - be attributed to higher migration rates and also higher birth rates (especially among the Hispanic population of the United States, which may partly help to counterbalance the shrinking and aging other domains of the US-population) . Europe, in contrast neither profits from a high migration rate, nor from population groups with high birth rates that could lead to a slowing of such socio-demographic change. This socio-demographic development in Europe is mirrored by the total birth rate in Germany: while it was at a considerably high(er) level in the 1960s, (both in the German Democratic Republic and the Federal Republic of Germany), it has fallen to a level below replacement rate, and as a consequence, the population has been steadily shrinking since 2003 .
Obviously, changes in an aging population will have meaningful impact upon the medical and health care sector . This prompts the question of how governments should deal with the increased need for potential long-term care, taking into account both the economic and ethical aspects that such care engenders. Moreover, cultural facets of this socio-demographic change must be considered, if genuine (ethically sound) attention is to be afforded to context-dependent needs of vulnerable populations such as the handicapped and fragile elderly.
Active Aging and Ambient Assistive Technologies as technological and political strategies to address problems of age-related sociodemographic change
Apparently, there is no facile, straightforward solution for this complex problem. However, to avoid the high cost of health insurance as well as to extend the period of independent and unrestricted living for the elderly population, it is vital to develop preventive techniques and technologies that allow the elderly - even under deteriorating health conditions - to live well and independently as long as possible. The European Union (EU) has focused a research and social innovation agenda upon programs that support what is called "active aging". Basic components of the "active ageing" strategy comprise life-long learning, extension of working life, later and gradual transit to retirement, an active life in retirement, as well as performance and health promoting innovations . As a consequence, the governing body of the EU has established a specific program dedicated to fostering research in the field of "Ambient Assisted Living" (AAL), and "Ambient Assistive Technologies" (AAT) as specific, integral components of AAL . AAL relates to concepts, products and services which combine and improve new technologies and social environment with the aim to increase life quality for people in all periods of life. They can also be understood as assistive systems particularly dedicated for a healthy and independent living of elders. Respective research projects in this context were invited for the first time in the 6th framework program (duration: 2002 - 2006) of the EU http://ec.europa.eu/research/fp6/index_en.cfm together with Information Society Technologies http://cordis.europa.eu/ist/.
AATs are designed to contain potential risks in households, by supporting the elderly in everyday activities. Intelligent technologies for an aging population may thereby be helpful for retaining and/or regaining health, and fostering independence, at least until residential care becomes unavoidable. AATs working with ubiquitous computing apply technology in a way that allows a "cloud of care" concept to be realized. This "cloud of care" has been suggested as a unobstrusive framework for integrating technology and providing services in a "smart" and non-invasive way to support people in the management of everyday activities (including medical services) in their homes .
In a recent survey, the major goals of technological systems designed to support older adults were summarized as [9
Assurance systems described by Pollack are aimed primarily at ensuring safety and well-being and reducing caregiver burden by tracking an elders' behavior(s) and providing real-time status reports (e.g. motion and position sensors).
Compensation systems to provide guidance to elderly individuals as they execute daily activities, reminding them of training or exercises and other necessities and how to do it (e.g. alarm-clocks for the intake of pharmaceuticals).
Assessment systems to infer a person's health, for example, by assessing cognitive level of function, based on continual observation of performance and/or monitoring of routine activities. These are subsumed by the term "AAL technologies".
Whereas assurance systems are already available as commercial products, compensation systems that actually intervene and assist elderly individuals in accomplishing daily activities mainly exist as research prototypes. According to Pollack , the challenge is primarily in the development of assessment systems that can provide continual, naturalistic assessment of the cognitive and affective status of older adults.
There are many venues for conceptualizing, designing and implementing compensation and assessment systems to assist daily activities as well as monitor psycho-physiological condition. Some of the most important environmental factors that affect the psycho-physiological condition of an individual are the surrounding lighting parameters. However, the age-dependency of lighting conditions has only recently become a focal research interest. The project "Ambient Lighting Assistance for an Ageing Population - ALADIN" was one of the first research endeavors to access the impact of light with special respect to the elderly population. In the following section, we describe the ALADIN project as an example for illustrating how AAT technologies can be employed to foster and/or retain elderly people's independence, health and quality of life.
Impact of Light on the Elderly and Reasons for Using Light in AAT
Physiological and pathological changes associated with the process of aging
It has recently been shown that the impact of light on the organism, and the reaction to environmental lighting conditions may substantially change with age . There are several functional and structural changes that may occur in the visual system (e.g. - particularly in the eye) as a consequence of aging. These include the reduced potential for adaptation of the visual system in elderly people. As the lens and iris become less flexible with progressing age, the retina receives less light, resulting in reduced retinal luminance and a need for increased light levels . Together with age-related diseases of the visual system, such as glaucoma or cataract, these changes lead to impaired vision and color perception.
Chrono-biologically, increased age incurs a gradual desynchronisation of sleep and wake cycles , thereby decreasing sleep quality, and also increasing the risk for specific sleep disorders that may decrease daytime vigilance, and correspondingly, quality of life. The sleep - wake cycle depends upon psychobiological "clocks" to synchronize the circadian rhythm with natural sunlight (or an artificial analogue). A poorly illuminated environment may incur negative physiologic effects and represents a risk factor for the desynchronisation of circadian regulation of the CNS and top-down psychophysiologic effects.
Ambient Natural Light: improving cognitive performance and reducing negative affect
Due to both physiological and behavioral changes (e.g. more indoor activity), elders are at risk of being exposed to less natural light. Reduced light may be a risk factor for well-being and should be taken into account, when defining the criteria for indoor conditions for this target group. Therefore it is crucial to investigate the temporal and spatial variables of light that need to be applied to mitigate possible negative health effects, and possibly proactively militate salutogenetic effects .
As these examples illustrate, elders may be at an increased risk of suffering from insufficient environmental lighting conditions. Thus, implementing higher standards for the indoor lighting conditions - i.e. higher levels of luminance and reduction of glare - for elderly individuals may be an important factor for improving their well-being. However, light conditions in older people's homes have not been a focus of architectural or building attention, and it may thus be assumed that many senior citizens live under suboptimal indoor lighting conditions. If this is to change, the challenge is to specify the lighting conditions (timing of light, its duration as well as its quantity, spectrum, and spatial distribution) to establish a high quality luminous environment specifically designed for the needs and demands of elderly individuals. In the ALADIN project this challenge was accepted. The focus of this paper lies within the discussion of ethical, social and legal aspects of ambient assistive technologies. Additionally, some considerations concerning AATs will be provided to address the possibility of AAL on a large scale. (A detailed description of the study and its results will be published in a forthcoming issue of Synesis- A Journal of Science, Technology, Ethics, and Policy). Additional information about the project is available online at http://www.ambient-lighting.eu.