Published in the journal Sleep, a report describing the study says that increasing daytime sleepiness symptoms over a five-year period were found to be associated with both poorer physical and mental quality of life.
Lead author Dr. Graciela E. Silva, an assistant professor in the College of Nursing and Health Innovation at Arizona State University, says that the findings provide important and surprising insights regarding the relationship between sleep and quality of life.
"While we were expecting an association between quality of sleep and quality of life, it was surprising that we did not find a significant association between objective measures of quality of sleep and quality of life, but that only subjective measures of sleep were associated with quality of life. These findings signal to the importance of perception of quality of sleep on quality of life," said Silva.
The study obtained polysomnographic and clinical data from 3,078 patients who were included in the baseline examination of the Sleep Heart Health Study (SHHS), a multi-center longitudinal study of participants over the age of 40.
The mean age of participants was 62 years at baseline and 67 years at follow-up. Fifty-five percent were women, and most were Caucasian (75 percent) and married (77 percent).
Coronary heart disease was more prevalent in men, and respiratory disease was more prominent in women.
The researchers obtained measures of quality of life using the Physical Component Summary (PCS) and Mental Component Summary (MCS) scales of the Medical Outcomes Study Short-Form Health questionnaire.
The primary exposure was change in the respiratory disturbance index (RDI) obtained from unattended overnight polysomnograms performed approximately five years apart.
Telling a bout their findings, the researchers said that the mean PCS dropped from 48.5 at baseline to 46.3 at follow-up, while the mean MCS increased slightly from 54.1 to 54.8.
They further said that significantly lower scores for women than men were seen at baseline and follow-up for the PCS and MCS.
According to them, Hispanics/Mexican Americans had lower baseline MCS and PCS scores compared with the other ethnic groups.
The team also observed that obese subjects had lower PCS scores than non-obese participants at baseline and follow-up; however, no difference was found for MCS at either survey.
Scores for both summary scales were lower for subjects with respiratory diseases and those taking sleeping pills, while PCS but not MCS scores were significantly lower for subjects with coronary heart disease.
Analysing their findings the authors say that the results suggest that physical limitations imposed by the presence of obesity, coronary heart disease and respiratory disease adversely impact physical components of quality of life.
They state that primary treatment to reduce morbidity and symptoms related to these conditions would ultimately improve sleep quality.