Label column in estimable table

[Eddy Simms]

I am trying to build a customisable table:

* Example generated by -dataex-. For more info, type help dataex
clear
input byte age int(sbp hr) double si byte transfusion
48 152  83 .5460526315789473 1
15 124 130 1.048387096774194 1
91 143 158 1.104895104895105 1
26  90 119 1.322222222222222 1
46  68 133 1.955882352941176 1
40  86 105 1.220930232558139 1
85  96  68 .7083333333333334 1
25  60 152 2.533333333333333 1
44 103 109 1.058252427184466 1
30  60  92 1.533333333333333 1
16 144 147 1.020833333333333 1
49  60  84               1.4 1
30 147  62 .4217687074829932 1
60  90  90                 1 1
80   . 102                 . 1
60 180  80 .4444444444444444 1
40 157 167 1.063694267515924 1
68  80 120               1.5 1
54  70  75 1.071428571428571 1
57 144  79 .5486111111111112 1
45  80  75             .9375 1
21  66 121 1.833333333333333 1
89 125 108              .864 1
32   .   .                 . 1
25  80 120               1.5 1
end
label values transfusion yn
label def yn 1 "Yes", modify
label var age "Age / Years"
label var sbp "Systolic Blood Pressure / mm Hg"
label var hr "Heart rate / bpm"
label var si "Shock Index"
label var transfusion "transfusion 1-yes 0-no"

collect clear
table (var) (transfusion),              ///
        stat(mean age hr sbp si) stat(sd age hr sbp si) ///
        stat(p50 age hr sbp si) stat(iqr age hr sbp si)
collect dims
collect levelsof result
collect recode result   ///
        mean = column1  ///
        sd = column2    ///
        p50 = column3   ///
        iqr = column4
collect label dim transfusion "Transfusion", modify
collect layout (var) (transfusion#result[column1 column2 column3 column4])
*collect style header result, level(hide)
collect style row stack, nobinder spacer
collect style cell var[age hr sbp si]#result[column1 column2 column3 column4], nformat(%6.1f)
collect preview

which gives me:

. collect preview

----------------------------------------------------------------------------------------------------------------
                                |                                   Transfusion                                 
                                |                   Yes                                    Total                
                                |  column1   column2   column3   column4   column1   column2   column3   column4
--------------------------------+-------------------------------------------------------------------------------
Age / Years                     |     47.0      22.5      45.0      30.0      47.0      22.5      45.0      30.0
Heart rate / bpm                |    107.5      29.8     106.5      44.0     107.5      29.8     106.5      44.0
Systolic Blood Pressure / mm Hg |    104.6      37.2      90.0      74.0     104.6      37.2      90.0      74.0
Shock Index                     |      1.2       0.5       1.1       0.6       1.2       0.5       1.1       0.6
----------------------------------------------------------------------------------------------------------------

[Eddy Simms]

Sorry - sent prematurely.
I would like to rename column1~column4 as mean, sd, p50, iqr but I cannot figure out how to do it.
Any advice gratefully received.
Thank you,
Eddy