Let the word be HEARTBEAT
If we lose heartbeat then we shall die
If we have 234 means "EAR" we can 1234 means "HEAR"
56 means "TB" is one type of disease
Exact time and location is indicated by 89 means "AT"
2&7 are same letter - "E"
3&8 are same letter - "A"
5&9 are same letter - "A"