1. What is the difference between life span and life expectancy? What characterizes centenarians? What sex difference exist in longevity?

1. What is the difference between life span and life expectancy? What characterizes centenarians? What sex difference exist in longevity?2. How do the circulatory and respiratory system change in older adults?3. What is the nature of sexuality in older adulthood?4. What characterizes substance abuse in late adulthood?5. How do exercise, nutrition and weight influence development in late adulthood?6. What are some options and issues in the health treatment of older adults?Please send references, thank you