| Value | Category | 
                                    
                    
                        | -99 | DK | 
                                    
                    
                        | -88 | Missing | 
                                    
                    
                        | -77 | NA | 
                                    
                    
                        | 1 | Once a day | 
                                    
                    
                        | 2 | More than once a day | 
                                    
                    
                        | 3 | Less than once a day | 
                                    
                    
                        | 4 | Never | 
                            
            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.