data age_grp;
   input pat_id age @@;
   cards;
290156 66 299871 68 280256 64 270456 60 262156 58
263256 55 266456 53 250656 44 251256 43 257456 47
258356 48 244606 42 249456 41 233256 33 237656 37
228356 28 222606 22 219856 21
;
run;

data agebygroup;
set age_grp;
if 20=<age<=34 then group='1';
if 35=<age<=49 then group='2';
if 50=<age<=64 then group='3';
if age>=65 then group='4';
run;

data agebygroup2;
set age_grp;
if 20=<age<=34 then group='1';
else if 35=<age<=49 then group='2';
else if 50=<age<=64 then group='3';
else if age>=65 then group='4';
run;