Vascular Health and Function in Cystic Fibrosis

The goal of this observational study is to learn whether blood vessel health and function differ between adults aged 40 years or older with cystic fibrosis (CF) who are taking CFTR modulator therapy and healthy adults of the same age and sex. As people with CF now live longer, they may face a higher risk of heart and blood vessel disease and stroke. The main question it aims to answer is: Is the function of the arteries in the arm (measured by radial artery flow-mediated dilation and low-flow mediated constriction) reduced in people with CF compared with healthy controls? Researchers will also compare the function of the neck (carotid) arteries, blood flow control in the brain, the reflexes that control blood pressure, and blood markers of inflammation and oxidative stress between the two groups. They will also look at whether these measures relate to memory and thinking, mood, and quality of life. Participants will attend a single study visit of about 2.5 to 3 hours at Liverpool Heart and Chest Hospital (or Manchester Metropolitan University for some healthy controls). During the visit they will: * Have height, weight, waist and hip size and body fat measured * Give a blood sample * Have ultrasound scans of the arm and neck arteries, including a short period with a blood pressure cuff inflated on the wrist and a few minutes with one hand in cold water * Have brain blood flow, heart rhythm, blood pressure and breathing monitored while resting, lying, standing, doing repeated squats and opening and closing their eyes * Complete short tests of memory and thinking, and questionnaires about mood and quality of life