How long do dogs live is a common question. The answer requires you to consider many factors, which include breed mix and size, and environmental influences. In general, smaller dogs live longer, from 14-22 years, with medium sized dogs living 11-14 years and large dogs living 8-12 years. Mixed breed dogs tend to live longer as many purebreds suffer from breed specific genetic problems that may shorten lifespan.
Diseases of the neurological system can also cause lethargy, and examples of these include fibromyalgia and Parkinson's disease. Diseases such as these have joint discomfort or stiffness, which may cause those affected to move less. Since they cannot move well without pain, this may increase their lethargy.
(countable and uncountable, plural lethargies). ( 1 pathology) A condition characterized by extreme fatigue or drowsiness, or prolonged sleep patterns. 2  A state of extreme torpor or apathy, especially with lack of emotion or interest; loosely, sluggishness, laziness. [from 14th c.].