The 'marginal decade' is the last decade of life, which for most people is characterized by poor quality of life due to significant declines in physical and cognitive health.

“marginal decade is the last decade of your life so everyone will have a marginal decade uh most people certainly don't know the day they enter it um sometimes you know when you're in it you know if you're especially if you're nearing the end of it a person probably has a sense of that appreciation but it is an important uh model because I think that the marginal decade for most people is really a period of poor life quality uh physical health has usually declined significantly cognitive Health potentially has declined as well”