More than 90 percent of patients with pulmonary arterial hypertension (PAH) report fatigue, but it has not been known if fatigue has an impact on physical activity in these patients.

Now, University of Pennsylvania researchers show that fatigue is tightly linked to daily physical activity, suggesting that interventions targeting fatigue might improve activity levels in PAH patients, possibly protecting them from further functional decline.

Fatigue takes its toll on the quality of life of PAH patients. Earlier studies showed that it is also associated with worsened breathing difficulties and psychological distress, as well as decreased functional capacity and cognitive function in these patients.

The study, ”Physical Activity and Symptoms in Pulmonary Arterial Hypertension,” set out to explore if fatigue, physical activity levels, and health-related quality of life were related in 15 women suffering from PAH. Their mean age was 50.5 years.

At the start of the study, scientists assessed the women’s severity of PAH and fatigue, and the participants performed a six-minute walk test (6MWT). They were then equipped with an accelerometer and instructed to keep an activity diary for seven days. On day 15 of the study, the women were assessed again and wore the accelerometer for another seven days.

Findings, published in the journal CHEST showed that the participants were sedentary 85 percent of the time, and performed low-level activities 10 percent of the time. There were no differences between measurements in the first and third week.

The researchers noted that less average daily activity was linked to the women’s reports of lower energy levels, but not to fatigue. Also, a low variability in day-to-day physical activity was associated with mental and physical fatigue as well as lower total activity levels. A low proportion of bouts of activity was also linked to low energy levels. In contrast, quality of life or severity of disease were not linked to daily activity counts.

Earlier studies have shown that mental fatigue can be an obstacle to engaging in physical activity. The authors, therefore, suggested that interventions to reduce fatigue might improve physical activity levels. However, the study was not designed to prove that fatigue prevents physical activity, and other studies have suggested the reverse relationship — that physical activity might lessen feelings of fatigue.

Researchers said that increased levels of physical activity would likely improve morbidity and mortality in PAH, but more studies are needed to confirm these relationships.