Physical activity may accurately predict mortality among idiopathic pulmonary fibrosis (IPF) patients, finds a German study, “Prognosis and longitudinal changes of physical activity in idiopathic pulmonary fibrosis,” that appeared in the journal BMC Pulmonary Medicine.

“A recent expert working group report suggested that besides primary survival analyses, the best evidence of the clinical efficacy of a treatment might be derived from direct measures of a patient’s symptoms and daily functions,” researchers wrote. “Therefore, measures of daily physical activity…might represent a clinically meaningful surrogate of a patient’s well-being and everyday functional status.”

Researchers at two German clinics —the Pulmonary Research Institute at LungenClinic Grosshansdorf and the Center for Interstitial and Rare Lung Diseases in Heidelberg — assessed whether physical activity could help predict all-cause mortality among 46 patients with IPF (mean age 67 years old) followed for three years.

They measured physical activity based on patients’ steps per day using a multisensory armband at baseline and at follow-up over a period of one week each. Patients wore the devices at all times except when attending to personal hygiene. The team also used several measures to analyze lung function and exercise capacity — such as the forced vital capacity (FVC), % predicted FVC (FVC% pred), and the 6-minute walking distance (6MWD) — as well as disease severity and progression.

Twenty patients died during the three-year follow-up period. At baseline, these patients had lower lung function, exercise capacity and physical activity than those who survived.

Further analyses indicated that steps per day and FVC % pred were the two measures that showed the best sensitivity and specificity to distinguish between survivors and non-survivors among IPF patients. Indeed, increases in these two parameters reduced risk of death by more than half.

Compared to baseline, steps per day declined by 973 steps (or 48.3 percent), FVC fell by 130 ml (13.3 percent), and 6MWD dropped by nine meters (or 7.8 percent).

“The main finding of our study is that objectively measured physical activity is a novel predictor of mortality in patients with IPF,” researchers wrote. “Furthermore, physical activity nearly halves in IPF patients surviving a follow-up period of three years. The ability to predict mortality is similar to established measures such as lung function, while physical activity decline in survivors is much more pronounced than suggested by longitudinal changes in lung function or 6MWD only.”