| Value | Category | 
                                    
                    
                        | 1 | Several times a day | 
                                    
                    
                        | 2 | Once a day | 
                                    
                    
                        | 3 | 2/3 days a week | 
                                    
                    
                        | 4 | Once a week | 
                                    
                    
                        | 5 | Other | 
                                    
                    
                        | 9 | Missing | 
                                    
                    
                        | Sysmiss |  | 
                            
            Warning: these figures indicate the number of cases found in the data file. They cannot be interpreted as summary statistics of the population of interest.