MUC5AC and chronic obstructive pulmonary disease: When all smokers (healthy smokers and COPD current smokers combined, n = 19) were compared with all nonsmokers (nonsmokers and COPD ex-smokers, n = 19), the smokers had a greater goblet cell density (8.69±3.69 vs. 4.02±3.23 cells/mm, p<.0001) and mucin volume density (22.49±13.73 vs. 8.08±7.46 μL/mm2, p<.0001).