section_path: Definitions/Sub-group definitions
section_name: Sub-group definitions
paragraph_text: Sub-group definitions
  
  Gerontologists have recognized that people experience very different conditions as they approach old age. In developed countries, many people in their later 60s and 70s (frequently called "early old age") are still fit, active, and able to care for themselves. However, after 80, they generally become increasingly frail, a condition marked by serious mental and physical debilitation.
  
  Therefore, rather than lumping together all people who have been defined as old, some gerontologists have recognized the diversity of old age by defining sub-groups. One study distinguishes the young-old (60 to 69), the middle-old (70 to 79), and the very old (80+). Another study's sub-grouping is young-old (65 to 74), middle-old (75 to 84), and oldest-old (85+). A third sub-grouping is young-old (65 to 74), old (74 to 84), and old-old (85+). Describing sub-groups in the 65+ population enables a more accurate portrayal of significant life changes.
  
  Two British scholars, Paul Higgs and Chris Gilleard, have added a "fourth age" sub-group. In British English, the "third age" is "the period in life of active retirement, following middle age". Higgs and Gilleard describe the fourth age as "an arena of inactive, unhealthy, unproductive, and ultimately unsuccessful ageing".