Bryndis Benediktsdottir

Prevalence of restless legs syndrome among adults in Iceland and Sweden: Lung function, comorbidity, ferritin, biomarkers and quality of life

OBJECTIVE This study investigates the prevalence and the association between restless legs syndrome (RLS) and a large variety of health variables in two well-characterized random samples from the general population in Reykjavik, Iceland, and Uppsala, Sweden. METHODS Using the national registries of inhabitants, a random sample from adults aged 40 and over living in Reykjavík, Iceland (n=939), and Uppsala, Sweden (n=998), were invited to participate in a study on the prevalence of COPD (response rate 81.1% and 62.2%). In addition, the participants were asked to answer the following questionnaires: International RLS Rating Scale, Short Form-12, the Epworth Sleepiness Scale, and questions about sleep, gastroeosophageal reflux, diabetes and hypertension, as well as pharmacological treatment. Interleukin-6 (IL-6), C-reactive protein (CRP) and ferritin were measured in serum. RESULTS RLS was more commonly reported in Reykjavik (18.3%) than in Uppsala (11.5%). Icelandic women reported RLS almost twice as often as Swedish women (24.4 vs. 13.9% p=0.001), but there was no difference in prevalence of RLS between Icelandic and Swedish men. RLS was strongly associated with sleep disturbances and excessive daytime sleepiness. Subjects with RLS were more likely to be ex- and current smokers than subjects without RLS (p<0.001). Respiratory symptoms and airway obstruction were more prevalent among those reporting RLS and they also estimated their physical quality of life lower than those without RLS (p<0.001). RLS was not associated with symptoms of the metabolic syndrome like hypertension, obesity, markers of systemic inflammation (IL-6 and CRP) or cardiovascular diseases. Ferritin levels were significantly lower in RLS participants (p=0.0002), but not (p=0.07) after adjustment for center, age, sex and smoking history. CONCLUSION Restless legs syndrome was twice as common among Icelandic women compared to Swedish women. No such difference was seen for men. RLS was strongly associated with smoking and respiratory symptoms, decreased lung function, sleep disturbances, excessive daytime sleepiness, and physical aspects of life quality. RLS was not associated with markers of the metabolic syndrome like hypertension, obesity, cardiovascular diseases or biomarkers of systemic inflammation.

The interaction of obstructive sleep apnea and obesity on the inflammatory markers C-reactive protein and interleukin-6: the Icelandic Sleep Apnea Cohort.

STUDY OBJECTIVES To assess the relative roles and interaction of obstructive sleep apnea (OSA) severity and obesity on interleukin-6 (IL-6) and C-reactive protein (CRP) levels. DESIGN Cross-sectional cohort. SETTING The Icelandic Sleep Apnea Cohort. PARTICIPANTS 454 untreated OSA patients (380 males and 74 females), mean ± standard deviation age 54.4 ± 10.6 yr. INTERVENTIONS N/A. MEASUREMENTS AND RESULTS Participants underwent a sleep study, abdominal magnetic resonance imaging to measure total abdominal and visceral fat volume, and had fasting morning IL-6 and CRP levels measured in serum. A significantly higher correlation was found for BMI than visceral fat volume with CRP and IL-6 levels. Oxygen desaturation index, hypoxia time, and minimum oxygen saturation (SaO₂) significantly correlated with IL-6 and CRP levels, but apnea-hypopnea index did not. When stratified by body mass index (BMI) category, OSA severity was associated with IL-6 levels in obese participants only (BMI > 30 kg/m²). A multiple linear regression model with interaction terms showed an independent association of OSA severity with IL-6 levels and an interaction between OSA severity and BMI, i.e., degree of obesity altered the relationship between OSA and IL-6 levels. An independent association of OSA severity with CRP levels was found for minimum SaO₂ only. A similar interaction of OSA severity and BMI on CRP levels was found for males and postmenopausal women. CONCLUSIONS OSA severity is an independent predictor of levels of IL-6 and CRP but interacts with obesity such that this association is found only in obese patients.

Chronic airflow obstruction and markers of systemic inflammation: Results from the BOLD study in Iceland

BACKGROUND Chronic obstructive pulmonary disease (COPD) is characterized by an irreversible chronic airflow obstruction and by an accelerated decline in lung function. Elevated circulating levels of C-reactive protein (CRP) and interleukin-6 (IL-6), both markers of systemic inflammation, have been found in COPD. Their possible associations with chronic airflow obstruction have mostly been evaluated in highly selected patient samples. Our objective was to evaluate the association between postbronchodilator lung function CRP and IL-6 in a randomly selected sample of the Icelandic population, 40 years and older, while adjusting for gender, age, smoking, and body weight. METHODS Serum CRP and IL-6 values were measured among participants in the Burden of Obstructive Lung Disease (BOLD) study. RESULTS Of the 938 subjects invited a total of 403 men and 355 women participated (response rate 81%) in the study. Their mean age (+/-SD) was 57.7 (+/-12.7) years. Both CRP and IL-6 were independently related to lower FEV1 and FVC values. Individuals in the highest quartiles of CRP and IL-6 had a 7.5% and 3.9%, respectively, lower FEV1% than predicted after adjustment for smoking, age, and body weight. High CRP levels were more strongly related to lower FEV1 levels in men (-11.4%) than in women (-0.4%). CONCLUSIONS In a random population-based sample both CRP and IL-6 were significantly related to lower spirometric values. The association with CRP was stronger in men than in women. This finding underscores the possible importance of systemic inflammation in irreversible airflow limitation.

The different clinical faces of obstructive sleep apnoea: a cluster analysis

Although commonly observed in clinical practice, the heterogeneity of obstructive sleep apnoea (OSA) clinical presentation has not been formally characterised. This study was the first to apply cluster analysis to identify subtypes of patients with OSA who experience distinct combinations of symptoms and comorbidities. An analysis of baseline data from the Icelandic Sleep Apnoea Cohort (822 patients with newly diagnosed moderate-to-severe OSA) was performed. Three distinct clusters were identified. They were classified as the “disturbed sleep group” (cluster 1), “minimally symptomatic group” (cluster 2) and “excessive daytime sleepiness group” (cluster 3), consisting of 32.7%, 24.7% and 42.6% of the entire cohort, respectively. The probabilities of having comorbid hypertension and cardiovascular disease were highest in cluster 2 but lowest in cluster 3. The clusters did not differ significantly in terms of sex, body mass index or apnoea–hypopnoea index. Patients with OSA have different patterns of clinical presentation, which need to be communicated to both the lay public and the professional community with the goal of facilitating care-seeking and early identification of OSA. Identifying distinct clinical profiles of OSA creates a foundation for offering more personalised therapies in the future. This study identified 3 different subtypes of patients with obstructive sleep apnoea based on clinical presentations http://ow.ly/AjuEZ

Present and future costs of COPD in Iceland and Norway: Results from the BOLD study

The Burden of Obstructive Lung Disease (BOLD) initiative provides standardised estimates of the burden of chronic obstructive pulmonary disease (COPD) worldwide. We estimate the current and future economic burden of COPD in Reykjavik, Iceland and Bergen, Norway using data from the BOLD initiative. Data on utilisation of healthcare resources were gathered from the BOLD survey, existing literature and unit costs from national sources. Economic data were applied to a Markov model using transition probabilities derived from Framingham data. Sensitivity analyses were conducted varying unit costs, utilisation and prevalence of disease. The cost of COPD was \#8364;478 per patient per yr in Iceland and \#8364;284 per patient per yr in Norway. The estimated cumulative costs of COPD for the population aged ≥40 yrs, were \#8364;130 million and \#8364;1,539 million for the following 10 yrs in Iceland and Norway, respectively. Costs of COPD accounted for 1.2 and 0.7% of healthcare budgets in Iceland and Norway, respectively. Sensitivity analyses showed estimates were most sensitive to changes in exacerbation frequency. COPD has a significant economic burden in both Iceland and Norway and will grow in the future. Interventions aimed at avoiding exacerbations will have the most impact on costs of COPD over the next 20 yrs.

Insomnia in untreated sleep apnea patients compared to controls

Insomnia and obstructive sleep apnea (OSA) often coexist, but the nature of their relationship is unclear. The aims of this study were to compare the prevalence of initial and middle insomnia between OSA patients and controls from the general population as well as to study the influence of insomnia on sleepiness and quality of life in OSA patients. Two groups were compared, untreated OSA patients (n = 824) and controls ≥ 40 years from the general population in Iceland (n = 762). All subjects answered the same questionnaires on health and sleep and OSA patients underwent a sleep study. Altogether, 53% of controls were males compared to 81% of OSA patients. Difficulties maintaining sleep (DMS) were more common among men and women with OSA compared to the general population (52 versus 31% and 62 versus 31%, respectively, P < 0.0001). Difficulties initiating sleep (DIS) and DIS + DMS were more common among women with OSA compared to women without OSA. OSA patients with DMS were sleepier than patients without DMS (Epworth Sleepiness Scale: 12.2 versus 10.9, P < 0.001), while both DMS and DIS were related to lower quality of life in OSA patients as measured by the Short Form 12 (physical score 39 versus 42 and mental score 36 versus 41, P < 0.001). DIS and DMS were not related to OSA severity. Insomnia is common among OSA patients and has a negative influence on quality of life and sleepiness in this patient group. It is relevant to screen for insomnia among OSA patients and treat both conditions when they co‐occur.

Symptoms of insomnia among patients with obstructive sleep apnea before and after two years of positive airway pressure treatment.

STUDY OBJECTIVES To assess the changes of insomnia symptoms among patients with obstructive sleep apnea (OSA) from starting treatment with positive airway pressure (PAP) to a 2-y follow-up. DESIGN Longitudinal cohort study. SETTING Landspitali--The National University Hospital of Iceland. PARTICIPANTS There were 705 adults with OSA who were assessed prior to and 2 y after starting PAP treatment. INTERVENTION PAP treatment for OSA. MEASUREMENTS AND RESULTS All patients underwent a medical examination along with a type 3 sleep study and answered questionnaires on health and sleep before and 2 y after starting PAP treatment. The change in prevalence of insomnia symptoms by subtype was assessed by questionnaire and compared between individuals who were using or not using PAP at follow-up. Symptoms of middle insomnia were most common at baseline and improved significantly among patients using PAP (from 59.4% to 30.7%, P < 0.001). Symptoms of initial insomnia tended to persist regardless of PAP treatment, and symptoms of late insomnia were more likely to improve among patients not using PAP. Patients with symptoms of initial and late insomnia at baseline were less likely to adhere to PAP (odds ratio [OR] 0.56, P = 0.007, and OR 0.53, P < 0.001, respectively). CONCLUSION Positive airway pressure treatment significantly reduced symptoms of middle insomnia. Symptoms of initial and late insomnia, however, tended to persist regardless of positive airway pressure treatment and had a negative effect on adherence. Targeted treatment for insomnia may be beneficial for patients with obstructive sleep apnea comorbid with insomnia and has the potential to positively affect adherence to positive airway pressure.

Obstructive sleep apnoea in the general population: highly prevalent but minimal symptoms.

The aim was to assess the prevalence of obstructive sleep apnoea (OSA) as defined by an apnoea–hypopnea index (AHI) ≥15 in the middle-aged general population, and the interrelationship between OSA, sleep-related symptoms, sleepiness and vigilance. A general population sample of 40–65-year-old Icelanders was invited to participate in a study protocol that included a type 3 sleep study, questionnaire and a psychomotor vigilance test (PVT). Among the 415 subjects included in the study, 56.9% had no OSA (AHI <5), 24.1% had mild OSA (AHI 5–14.9), 12.5% had moderate OSA (AHI 15–29.9), 2.9% had severe OSA (AHI ≥30) and 3.6% were already diagnosed and receiving OSA treatment. However, no significant relationship was found between AHI and subjective sleepiness or clinical symptoms. A relationship with objective vigilance assessed by PVT was only found for those with AHI ≥30. Subjects already on OSA treatment and those accepting OSA treatment after participating in the study were more symptomatic and sleepier than others with similar OSA severity, as assessed by the AHI. In a middle-aged general population, approximately one in five subjects had moderate-to-severe OSA, but the majority of them were neither symptomatic nor sleepy and did not have impaired vigilance. Overall, 15% of the general population had untreated OSA without symptoms, sleepiness or decreased vigilance http://ow.ly/StiqS

The prevalence of chronic obstructive pulmonary disease in Uppsala, Sweden – the Burden of Obstructive Lung Disease (BOLD) study: cross-sectional population-based study

Objectives:  To estimate chronic obstructive pulmonary disease (COPD) prevalence in Uppsala and the impact of risk factors on disease prevalence using the standardised methods of the Burden of Obstructive Lung Disease (BOLD) study initiative.

The role of obesity, different fat compartments and sleep apnea severity in circulating leptin levels: the Icelandic Sleep Apnea Cohort study

Objectives:To assess whether sleep apnea severity has an independent relationship with leptin levels in blood after adjusting for different measures of obesity and whether the relationship between obstructive sleep apnea (OSA) severity and leptin levels differs depending on obesity level.Methods:Cross-sectional study of 452 untreated OSA patients (377 males and 75 females), in the Icelandic Sleep Apnea Cohort (ISAC), age 54.3±10.6 (mean±s.d.), body mass index (BMI) 32.7±5.3 kg m−2 and apnea-hypopnea index 40.2±16.1 events per h. A sleep study and magnetic resonance imaging of abdominal visceral and subcutaneous fat volume were performed, as well as fasting serum morning leptin levels were measured.Results:Leptin levels were more highly correlated with BMI, total abdominal and subcutaneous fat volume than visceral fat volume per se. No relationship was found between sleep apnea severity and leptin levels, assessed within three BMI groups (BMI <30, BMI 30–35 and BMI ⩾35 kg m−2). In a multiple linear regression model, adjusted for gender, BMI explained 38.7% of the variance in leptin levels, gender explained 21.2% but OSA severity did not have a significant role and no interaction was found between OSA severity and BMI on leptin levels. However, hypertension had a significant effect on the interaction between OSA severity and obesity (P=0.04). In post-hoc analysis for nonhypertensive OSA subjects (n=249), the association between leptin levels and OSA severity explained a minor but significant variance (3.2%) in leptin levels. This relationship was greatest for nonobese nonhypertensive subjects (significant interaction with obesity level). No relationship of OSA severity and leptin levels was found for hypertensive subjects (n=199).Conclusion:Obesity and gender are the dominant determinants of leptin levels. OSA severity is not related to leptin levels except to a minor degree in nonhypertensive nonobese OSA subjects.