Pulmonary fibrosis (PF) is a respiratory condition characterized by the thickening and scarring (or fibrosis) of the lungs. As a result, it is difficult for oxygen to pass through the air sacs and into the bloodstream, causing symptoms such as shortness of breath and a dry cough.
Environmental pollutants, some medicines, connective tissue diseases, and interstitial lung diseases are noted as some of the causes that lead to PF. But in most of the cases, the cause is unknown, in which case the disease is called idiopathic pulmonary fibrosis (IPF).
The average survival in IPF is poor, with only 20 to 30 percent of people surviving at least five years after diagnosis. The most frequent cause of death is respiratory failure. Some of the factors that have been shown to affect survival include older age, smoking history, lower body mass index (BMI), and greater radiologic extent of the disease. However, there is no established method of combining these predictors to accurately determine the prognosis or define the stage of IPF.
This section offers readers information about age as a factor that influences the prognosis of PF.
According to a review article, which examined and summarized clinical data on individual predictors of survival, 66 is the average age when PF is diagnosed, and the older the age of diagnosis, the poorer the prognosis. In another study in adults ages 35 to 44, the prevalence of IPF is 2.7 per 100,000 people, while in adults who are 75 and older this ratio is 157 per 100,000 people. A study by Talmadge E. King Jr. and colleagues estimates survival to be 81 months (6.71 years) from the start of disease and 35 months (2.9 years) from the time of the initial clinical visit. The authors also concluded that survival is significantly related to age and other factors such as finger clubbing, smoking history, profusion of interstitial opacities, evidence of pulmonary hypertension on chest radiography, reduced lung volume, and gas exchange abnormalities with exercise.
A 2006 study estimated the annual incidence and prevalence of IPF in the U.S. The value was calculated for each age and gender-specific stratum. In people ages 18 to 34, the prevalence of IPF was estimated to be 1.2 per 100,000 people, while for people ages 75 and older it was estimated to be 76.4 per 100,000.
Charlene Fell and colleagues, in a 2009 study, suggested that age combined with findings from high resolution computed tomography (HRCT) are useful to diagnose people with IPF. In people who are 75 and older, the predictive value of confirming IPF by surgical lung biopsy is 100 percent. In people who are 70, the predictive value is at least 95 percent. Increased age was found to be a strong predictor of IPF in people with early radiographic signs of the disease. These findings are consistent with the progression of IPF as a degenerative disease.
Other data has suggested that age-related changes in cellular function may play a central role in IPF. Aging is associated with oxidation of proteins such as glutathione (a protein involved in the prevention of damage to cells, processing medications and carcinogens, and building of DNA, proteins, and other cellular components), and alterations in mesenchymal stem cell function. Both these changes contribute to abnormalities of alveolar epithelial regeneration that have been found in people with IPF. Other age-related conditions (such as cognitive impairment, malnutrition, and frailty) may also contribute to the severity of symptoms and possibly to the progression of IPF.
Overall, the incidence of IPF is higher in older people, with the average survival being two to three years after diagnosis. Age can be used as a predicting factor for the prognosis of IPF and a tool to diagnose the condition.
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