Worse Lung Function, Higher BMI Linked to Lower Quality of Life

Margarida Maia, PhD avatar

by Margarida Maia, PhD |

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Poorer lung function and a higher body mass index (BMI), a measure indicating obesity, are significantly associated with a lower self-reported quality of life in people with sarcoidosis, a German study found.

Of note, the tool used to assess quality of life — called the King’s Sarcoidosis Questionnaire or KSQ — provided relevant information about each patient’s health status that went beyond what was obtained during routine follow-up.

“The questionnaire may represent a tool in patient care and also a relevant instrument for clinical studies in sarcoidosis,” the researchers wrote.

The study, “FeV1 and BMI influence King’s Sarcoidosis Questionnaire score in sarcoidosis patients,” was published in BMC Pulmonary Medicine. 

Sarcoidosis is a disease in which granulomas (abnormal clumps of inflammatory cells) form in many organs of the body, most commonly in the lungs. In addition to causing impairments in organ functioning, disease symptoms such as fatigue or cough may have a significant impact on quality of life.

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The KSQ was originally developed in the U.K. as a tool to assess self-reported quality of life specifically among people with sarcoidosis. The questionnaire has several modules, which cover general health status (GHS), as well as quality of life associated with the lungs (LUNG), skin (SKIN), eyes (EYE), and use of medication (MED). Each module is scored from zero to 100 and scores can be combined to form a composite score.

A team of researchers in Germany recently translated the KSQ to German and validated their version in a group of sarcoidosis patients. Now, they aimed to determine which clinical factors affect the results of the KSG.

The study (DRKS00010072) included 200 German-speaking sarcoidosis patients with a mean age of 53. Among them were 103 men and 97 women. KSG scores tended to be lower in men than in women, but the difference was only significant for a composite score of GHS, SKIN, and MED.

The GHS score correlated with each of the other four domains, but most strongly with the LUNG score. Based on this finding, the researchers set out to determine the extent to which clinical parameters may affect the LUNG score.

Of all lung function parameters, FEV1 — a measure of the amount of air that can be forcedly exhaled from the lungs in one second — exerted the greatest effect on the LUNG score, and this was seen for both men and women.

Another lung function parameter was called DLCO, short for diffusing capacity for carbon monoxide, a measure of the ability of gas to transfer from the lungs to the red blood cells. The DLCO also correlated with the LUNG score.

When researchers added body mass index, known as BMI — a measure of body fat based on weight and height — into the equation, they found that it correlated negatively with the LUNG score. In fact, an increase in BMI by one point was associated with a decrease in LUNG scores by 1.09 points. Of note, a high BMI score is indicative of obesity.

These findings suggest that the LUNG score may only partially be determined by lung function.

Consistent with the impact of the LUNG scores in GHS, this assessment of general health status also was positively associated with better FEV1 scores and negatively correlated with higher BMI.

“Notably, high BMI is significantly negatively associated with patients’ well-being as measured by KSQ-GHS,” the team wrote.

The researchers noted that obesity “has been recognized as prevalent” in people with sarcoidosis — and as affecting patients’ quality of life.

“Vice versa reduced quality of life may result in inactivity and obesity resulting in a vicious circle,” they wrote.

The team questioned whether changes in diet or other lifestyle modifications would have an impact on this parameter.

“KSQ adds important additional information to routinely monitored parameters in sarcoidosis care,” the researchers wrote, adding that such information is of relevance for patient monitoring and for clinical decision-making.

Treatment of sarcoidosis, when necessary, begins with steroid medications, which are often associated with significant weight gain. Thus, the association between a higher BMI and lower health status may further emphasize the need to treat patients with steroid-sparing therapies such as immunosuppressants.

“This observation [that BMI affects KSQ scores] may direct further studies investigating the effect of obesity on sarcoidosis-related quality of life and strategies to intervene with steroid-sparing therapies and measures of life style modifications,” the researchers concluded.