Hi Vicky,
Your posting caught my attention so I went on to read online and ask my doctor friends. Although I can't represent what doctors say, what I've heard is that Alzheimers doesn't cause the airways to narrow. However, old age is the most viable reason for that to happen.
An abstract from The American Society of Anesthesiologists (Geriatrics):
"Physiologically, aging also affects the respiratory system with decreases in responsiveness to hypercapnia, and often with hypoxia due to decreased carotid and aortic body sensitivities. There is an increase in chest wall rigidity, chest wall compliance and muscle strength. Also, as the airway from the nose to the terminal bronchi become more narrow or stiff, there is a decrease in the exchange of gas. The lung parenchyma contains three important gas exchange structures: 1) alveolar, the gas exchange airways distal to the terminal bronchioles, 2) capillary bed and 3) the interstitial structure of the lung (elastic recoil). Under normal situations, the distal airways maintain patent by the elastic recoil forces of the surrounding lung parenchyma. The forces that hold intraparenchymal airways (small airways) open will therefore decrease as the aging lung loses its elastic recoil due to thickening of parenchyma. The thickening of parenchyma will also decrease gas exchange between the alveolar and capillary bed. There is ventilation perfusion mismatching and decreased arterial oxygen.
The respiratory system is also affected by environmental changes, including smoke, dust, air pollution, etc. Respiratory diseases include emphysema, dyspnea, and hypoxia."
Hence, it may be possible to conclude that narrow airways is one of the many changes exhibited in a person who is aging (unless IF she has Asthma).