gap – n. a difference between two people, groups or things (often + between)

life expectancy – n. the average number of years that a person or animal can expect to live

engage – v. to get and keep (someone’s attention, interest, etc.)

mask – v. to keep (something) from being known or noticed

risk factor – n. something that increases risk

life span – n. the amount of time that a person or animal actually lives

socioeconomic – adj. of, relating to or involving a combination of social and economic factors

background – n. the experiences, knowledge, education, etc., in a person's past
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