OOP, missing dementia, fixed 5 yr sample

Brought months variables from OOP into full dataset
Looking at those with missing dementia probability, checked age at
interview, interview wave and other related variables that could be used
to backfill when probability is missing
Filled in missing helper details for obs where helper information is
missing to get final tables
Added requirement age>=70 for inclusion into 5 year lookback sample
SIC added info re missing p1 ivws

Added rows to the tables in the last section, identify those that die
within 2 years of meeting criteria, they don't have the p1 interview