| Value | Category | Cases | |
|---|---|---|---|
| -9 | Don't know (spontaneous) | 5 | 
                                    
                                    6.7%
                                 | 
| 1 | One month or less | 8 | 
                                    
                                    10.7%
                                 | 
| 2 | 10 | 
                                    
                                    13.3%
                                 | |
| 3 | 39 | 
                                    
                                    52%
                                 | |
| 4 | 4 | 
                                    
                                    5.3%
                                 | |
| 5 | 1 | 
                                    
                                    1.3%
                                 | |
| 6 | 5 | 
                                    
                                    6.7%
                                 | |
| 7 | 1 | 
                                    
                                    1.3%
                                 | |
| 12 | 2 | 
                                    
                                    2.7%
                                 | |
| Sysmiss | 570 |