********************************************************************
* File			    HALCyon body size syntax_NSHD.do
* BY				Rebecca Hardy, MRC Unit for Lifelong Health and Ageing at UCL
* FOR				HALCyon cross-cohort collaboration (funded by the New Dynamics of Ageing (RES-353-25-0001))
* DATASET			MRC National Survey of Health and Development
* Date Created 		12/05/2010
* last modified	    12/05/2010

* PURPOSE			Recodes and derives body size variables for use in cross-cohort analyses
*************************************************************************************

# delimit;
set more off;

/*current body size*/
mvdecode bmi99u ht99u, mv(9999,7777) ;
mvdecode abc hipc, mv(999, 999.9) ;
replace abc=. if abc<1 ;
replace hipc=. if hipc<1 ;

/*birth weight*/
mvdecode mbwtu, mv(9999) ;
gen mbwtkg=mbwtu/1000 ;

/*earlier adult body size*/
mvdecode bmi66u bmi72u bmi82u bmi89u ht66u ht82u ht89u, mv(9999,7777,9997,9998) ;
/*compute z-scores and z-score velocities - separately by sex*/
egen bmi66m=std(bmi66u) if sex==1 ;
egen bmi66f=std(bmi66u) if sex==2 ;

gen bmi66z=. ;
replace bmi66z=bmi66m if sex==1 ; 
replace bmi66z=bmi66f if sex==2 ; 

egen bmi72m=std(bmi72u) if sex==1 ;
egen bmi72f=std(bmi72u) if sex==2 ;

gen bmi72z=. ;
replace bmi72z=bmi72m if sex==1 ; 
replace bmi72z=bmi72f if sex==2 ; 

egen bmi82m=std(bmi82u) if sex==1 ;
egen bmi82f=std(bmi82u) if sex==2 ;

gen bmi82z=. ;
replace bmi82z=bmi82m if sex==1 ; 
replace bmi82z=bmi82f if sex==2 ; 

egen bmi89m=std(bmi89u) if sex==1 ;
egen bmi89f=std(bmi89u) if sex==2 ;

gen bmi89z=. ;
replace bmi89z=bmi89m if sex==1 ; 
replace bmi89z=bmi89f if sex==2 ;

egen bmi99m=std(bmi99u) if sex==1 ;
egen bmi99f=std(bmi99u) if sex==2 ;

gen bmi99z=. ;
replace bmi99z=bmi99m if sex==1 ; 
replace bmi99z=bmi99f if sex==2 ; 


/*velocities*/

gen bmi6672=(bmi72u-bmi66u)/6 ;

egen bmi6672m=std(bmi6672) if sex==1 ;
egen bmi6672f=std(bmi6672) if sex==2 ;

gen bmi6672z=. ;
replace bmi6672z=bmi6672m if sex==1 ; 
replace bmi6672z=bmi6672f if sex==2 ;

gen bmi7282=(bmi82u-bmi72u)/10 ;

egen bmi7282m=std(bmi7282) if sex==1 ;
egen bmi7282f=std(bmi7282) if sex==2 ;

gen bmi7282z=. ;
replace bmi7282z=bmi7282m if sex==1 ; 
replace bmi7282z=bmi7282f if sex==2 ; 

gen bmi8289=(bmi89u-bmi82u)/7 ;

egen bmi8289m=std(bmi8289) if sex==1 ;
egen bmi8289f=std(bmi8289) if sex==2 ;

gen bmi8289z=. ;
replace bmi8289z=bmi8289m if sex==1 ; 
replace bmi8289z=bmi8289f if sex==2 ;

gen bmi8999=(bmi99u-bmi89u)/10 ;

egen bmi8999m=std(bmi8999) if sex==1 ;
egen bmi8999f=std(bmi8999) if sex==2 ;

gen bmi8999z=. ;
replace bmi8999z=bmi8999m if sex==1 ; 
replace bmi8999z=bmi8999f if sex==2 ;

/*velocities to match with Boyd Orr data 20-43, 43-current (53)*/
gen bmi6689=(bmi89u-bmi66u)/23 ;

egen bmi6689m=std(bmi6689) if sex==1 ;
egen bmi6689f=std(bmi6689) if sex==2 ;

gen bmi6689z=. ; 
replace bmi6689z=bmi6689m if sex==1 ; 
replace bmi6689z=bmi6689f if sex==2 ;



/*age at which first overweight*/

gen owt66=bmi66u ;
recode owt66 (min/24.9999=0) (25/max=1) ;

gen owt72=bmi72u ;
recode owt72 (min/24.9999=0) (25/max=1) ;

gen owt82=bmi82u ;
recode owt82 (min/24.9999=0) (25/max=1) ;

gen owt89=bmi89u ;
recode owt89 (min/24.9999=0) (25/max=1) ;

gen owt99=bmi99u ;
recode owt99 (min/24.9999=0) (25/max=1) ;


/*age at first overweight 26-52 years*/

gen ageowt=. ;
replace ageowt=0 if owt99==0 ;
replace ageowt=1 if owt99==1 ;
replace ageowt=2 if owt89==1 ;
replace ageowt=3 if owt82==1 ;
replace ageowt=4 if owt72==1 ;