<Li> applying this knowledge to policies and programs, including the macroscopic (for example, government planning) and microscopic (for example, running a nursing home) perspectives . </Li> <P> The multidisciplinary nature of gerontology means that there are a number of sub-fields, as well as associated fields such as physiology, anthropology, social work, public health, psychology and sociology that overlap with gerontology . </P> <P> In the medieval Islamic world, several physicians wrote on issues related to Gerontology . Avicenna's The Canon of Medicine (1025) offered instruction for the care of the aged, including diet and remedies for problems including constipation . Arabic physician Ibn Al - Jazzar Al - Qayrawani (Algizar, c. 898--980) wrote on the aches and conditions of the elderly (Ammar 1998, p. 4). His scholarly work covers sleep disorders, forgetfulness, how to strengthen memory, and causes of mortality Ishaq ibn Hunayn (died 910) also wrote works on the treatments for forgetfulness (U.S. National Library of Medicine, 1994). </P> <P> While the number of aged humans, and the life expectancy, tended to increase in every century since the 14th, society tended to consider caring for an elderly relative as a family issue . It was not until the coming of the Industrial Revolution that ideas shifted in favor of a societal care - system . </P>

When did researchers begin to study the aging process
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