TROMSO_SMO_START

Variable SMOKE_START_AGE_T4 : If you currently smoke, or have smoked before, how old were you when you began smoking daily?

SAS code:

dif2=AGE_T4 - SMOKE_START_AGE_T4;

If SMOKE_START_AGE_T4 NE . and dif2 LE 0 then SMOKE_START_AGE_T4=.;

If SMOKE_START_AGE_T4 NE . and dif2 IN (1 2 3 4 5) then SMOKE_START_AGE_T4=.;

SMO_START=SMOKE_START_AGE_T4;

IF SMO_START EQ . then SMO_START=9999;      

MORGAM_SMO_START

The SMO_START variable is defined using the MORGAM variable CIGAGE and the CHANCES variable SMO_STAT_DAILY:

CIGAGE
"How old were you when you began to smoke cigarettes regularly?"
88 if EVERCIG = 2
99 = insufficient data

HAPIEE_SMO_START

Based on HAPIEE baseline variable l41, age at which started smoking for current and past smokers. 

Stata  code 

replace l41=. if l41==.b |  l41==.c
gen smo_start=l41
replace smo_start=9999 if l41==.

ESTHER_SMO_START

smo_start = cigage;
if smo_stat_daily in (2,3) and smo_start = . then smo_start = 9999;

Variable cigage is derived from L41RAU1 from participant's questionnaire at baseline. smo_stat_daily is a CHANCES variable.

EPIC_SMO_START

The variables A_CIGARS, A_STA_CIG_AGGR, A_STA_SMOK_AGGR, A_PIPE were used for the production of SMO_START according to the following definition and rule.

EPIC var definition(s):
A_CIGARS: Epic elderly variable showing age at the cigar smoking onset.

A_STA_CIG_AGGR: Epic elderly variable showing age at cigarette smoking onset.

A_STA_SMOK_AGGR: Epic elderly variable showing age at smoking onset.

A_PIPE: Epic elderly variable showing age at pipe smoking onset.

SMOKE_ST: Epic elderly variable showing smoking status (1=never, 2=former, 3=smoker, 4=unknown)

Coding rule:
Variable SMO_START shows the age at which the person started smoking. Is the minimum value among A_CIGARS, A_STA_CIG_AGGR, A_STA_SMOK_AGGR, A_PIPE, given that the person has been a former or a current smoker ((SMOKE_ST~=1 &SMOKE_ST~=4)

Otherwise SMO_START is equal to 9999.

Coding rule in STATA:
-egen SMO_START = rowmin(A_CIGARS A_STA_CIG_AGGR A_STA_SMOK_AGGR A_PIPE) if (SMOKE_ST~=1 &SMOKE_ST~=4)

-recode SMO_START .=9999