| 1. |
- Arnardottir, Erna Sif, et al.
(author)
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Nocturnal sweating - a common symptom of obstructive sleep apnoea : the Icelandic sleep apnoea cohort
- 2013
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In: BMJ Open. - : BMJ. - 2044-6055. ; 3:5, s. e002795-
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Journal article (peer-reviewed)abstract
- Objectives: To estimate the prevalence and characteristics of frequent nocturnal sweating in obstructive sleep apnoea (OSA) patients compared with the general population and evaluate the possible changes with positive airway pressure (PAP) treatment. Nocturnal sweating can be very bothersome to the patient and bed partner. Design: Case-control and longitudinal cohort study. Setting: Landspitali-The National University Hospital, Iceland. Participants: The Icelandic Sleep Apnea Cohort consisted of 822 untreated patients with OSA, referred for treatment with PAP. Of these, 700 patients were also assessed at a 2-year follow-up. The control group consisted of 703 randomly selected subjects from the general population. Intervention: PAP therapy in the OSA cohort. Main outcome measures: Subjective reporting of nocturnal sweating on a frequency scale of 1-5: (1) never or very seldom, (2) less than once a week, (3) once to twice a week, (4) 3-5 times a week and (5) every night or almost every night. Full PAP treatment was defined objectively as the use for = 4 h/day and = 5 days/week. Results: Frequent nocturnal sweating (= 3x a week) was reported by 30.6% of male and 33.3% of female OSA patients compared with 9.3% of men and 12.4% of women in the general population (p<0.001). This difference remained significant after adjustment for demographic factors. Nocturnal sweating was related to younger age, cardiovascular disease, hypertension, sleepiness and insomnia symptoms. The prevalence of frequent nocturnal sweating decreased with full PAP treatment (from 33.2% to 11.5%, p<0.003 compared with the change in non-users). Conclusions: The prevalence of frequent nocturnal sweating was threefold higher in untreated OSA patients than in the general population and decreased to general population levels with successful PAP therapy. Practitioners should consider the possibility of OSA in their patients who complain of nocturnal sweating.
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| 2. |
- Benediktsdottir, Asdis, et al.
(author)
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Ambient noise tomography of Eyjafjallajokull volcano, Iceland
- 2017
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In: Journal of Volcanology and Geothermal Research. - : Elsevier BV. - 0377-0273 .- 1872-6097. ; 347, s. 250-263
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Journal article (peer-reviewed)abstract
- We present a shear-velocity model for the Eyjafjallajokull stratovolcano, based on ambient seismic noise tomography applied to seven months of data from six permanent stations and -10 temporary seismic stations, deployed during and after the 2010 volcanic unrest. Vertical components of noise were cross correlated resulting in 30 robust phase-velocity dispersion curves between 1.6 and 6.5 s in period, displaying a +/- 20% variation in phase velocity beneath the volcano. The uneven distribution of noise sources, evaluated using signal-to-noise ratios, was estimated to cause less than 2% error in most curves. Sensitivity kernels showed resolution down to 10 km and the lateral resolution of the resulting phase-velocity maps was about 5 km. The model reveals east-west oriented high-velocity anomalies due east and west of the caldera. Between these a zone of lower velocity is identified, coinciding with the location of earthquakes that occurred during the summit eruption in April 2010. A shallow, southwest elongated low-velocity anomaly is located 5 km southwest of the caldera. The limited depth resolution of the shear-velocity model precludes detection of melt within the volcano.
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| 3. |
- Benediktsdottir, Asdis, et al.
(author)
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Volcanic tremor of the 2010 Eyjafjallajökull eruption
- 2022
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In: Geophysical Journal International. - : Oxford University Press. - 0956-540X .- 1365-246X. ; 228:2, s. 1015-1037
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Journal article (peer-reviewed)abstract
- Volcanic eruptions in Iceland generally start with an increase in tremor levels. These signals do not have clear onset, like many earthquakes. As the character of the tremor signal is variable from one volcano to another, locating the source of the tremor signal may require different techniques for different volcanoes. Continuous volcanic tremor varied considerably during the course of the Eyjafjallajökull summit eruption, 14 April to 22 May 2010, and was clearly associated with changes in eruptive style. The tremor frequencies ranged between 0.5 and 10 Hz, with increased vigour during an effusive and explosive phase, in comparison with purely explosive phases. Higher-frequency tremor bursts early in the eruption were caused by processes at the eruption site. Location of the tremor using a method based on differential phase information extracted from interstation correlograms showed the tremor to be stable near the eruption vent, through time, for signals between 0.5 and 2 Hz. Analyses of power variations of the vertical component of the tremor with distance from the eruption site are consistent with tremor waveform content being dominated by surface waves in the 0.5–2 Hz frequency range. The tremor source depth was argued to be shallow, less than about 1 km. The attenuation quality factor (Q) was found to be on the order of Q = 10–20 for paths in the area around Eyjafjallajökull and Q = 20–50 for paths outside the volcano. The pattern of radiated wave energy from the tremor source varied with time, defining ten different epochs during the eruption. Thus the tremor-source radiation did not remain isotropic, which needs to be considered when locating tremor based on amplitude, that is azimuthally variable source radiation.
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| 4. |
- Benediktsdottir, Bryndis, et al.
(author)
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Prevalence of restless legs syndrome among adults in Iceland and Sweden : Lung function, comorbidity, ferritin, biomarkers and quality of life
- 2010
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In: Sleep Medicine. - : Elsevier BV. - 1389-9457 .- 1878-5506. ; 11:10, s. 1043-1048
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Journal article (peer-reviewed)abstract
- 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.
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| 5. |
- Bjornsdottir, Erla, et al.
(author)
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Association between physical activity over a 10-year period and current insomnia symptoms, sleep duration and daytime sleepiness : a European population-based study
- 2024
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In: BMJ Open. - : BMJ Publishing Group Ltd. - 2044-6055. ; 14:3
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Journal article (peer-reviewed)abstract
- OBJECTIVES: To explore the relationship between physical activity over a 10-year period and current symptoms of insomnia, daytime sleepiness and estimated sleep duration in adults aged 39-67.DESIGN: Population-based, multicentre cohort study. SETTING: 21 centres in nine European countries.METHODS: Included were 4339 participants in the third follow-up to the European Community Respiratory Health Survey (ECRHS III), who answered questions on physical activity at baseline (ECRHS II) and questions on physical activity, insomnia symptoms, sleep duration and daytime sleepiness at 10-year follow-up (ECRHS III). Participants who reported that they exercised with a frequency of at least two or more times a week, for 1 hour/week or more, were classified as being physically active. Changes in activity status were categorised into four groups: persistently non-active; became inactive; became active; and persistently active.MAIN OUTCOME MEASURES: Insomnia, sleep time and daytime sleepiness in relation to physical activity.RESULTS: Altogether, 37% of participants were persistently non-active, 25% were persistently active, 20% became inactive and 18% became active from baseline to follow-up. Participants who were persistently active were less likely to report difficulties initiating sleep (OR 0.60, 95% CI 0.45-0.78), a short sleep duration of ≤6 hours/night (OR 0.71, 95% CI 0.59-0.85) and a long sleep of ≥9 hours/night (OR 0.53, 95% CI 0.33-0.84) than persistently non-active subjects after adjusting for age, sex, body mass index, smoking history and study centre. Daytime sleepiness and difficulties maintaining sleep were not related to physical activity status.CONCLUSION: Physically active people have a lower risk of some insomnia symptoms and extreme sleep durations, both long and short.
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| 6. |
- Bjornsdottir, Erla, et al.
(author)
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Association between physical activity over a 10-year period and current insomnia symptoms, sleep duration and daytime sleepiness: a European population-based study
- 2024
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In: BMJ OPEN. - : BMJ Publishing Group Ltd. - 2044-6055. ; 14:3
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Journal article (peer-reviewed)abstract
- Objectives To explore the relationship between physical activity over a 10-year period and current symptoms of insomnia, daytime sleepiness and estimated sleep duration in adults aged 39-67. Design Population-based, multicentre cohort study. Setting 21 centres in nine European countries. Methods Included were 4339 participants in the third follow-up to the European Community Respiratory Health Survey (ECRHS III), who answered questions on physical activity at baseline (ECRHS II) and questions on physical activity, insomnia symptoms, sleep duration and daytime sleepiness at 10-year follow-up (ECRHS III). Participants who reported that they exercised with a frequency of at least two or more times a week, for 1 hour/week or more, were classified as being physically active. Changes in activity status were categorised into four groups: persistently non-active; became inactive; became active; and persistently active. Main outcome measures Insomnia, sleep time and daytime sleepiness in relation to physical activity. Results Altogether, 37% of participants were persistently non-active, 25% were persistently active, 20% became inactive and 18% became active from baseline to follow-up. Participants who were persistently active were less likely to report difficulties initiating sleep (OR 0.60, 95% CI 0.45-0.78), a short sleep duration of <= 6 hours/night (OR 0.71, 95% CI 0.59-0.85) and a long sleep of >= 9 hours/night (OR 0.53, 95% CI 0.33-0.84) than persistently non-active subjects after adjusting for age, sex, body mass index, smoking history and study centre. Daytime sleepiness and difficulties maintaining sleep were not related to physical activity status. Conclusion Physically active people have a lower risk of some insomnia symptoms and extreme sleep durations, both long and short.
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| 7. |
- Bjornsdottir, Erla, et al.
(author)
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Quality of life among untreated sleep apnea patients compared with the general population and changes after treatment with positive airway pressure
- 2015
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In: Journal of Sleep Research. - : Wiley. - 0962-1105 .- 1365-2869. ; 24:3, s. 328-338
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Journal article (peer-reviewed)abstract
- Obstructive sleep apnea leads to recurrent arousals from sleep, oxygen desaturations, daytime sleepiness and fatigue. This can have an adverse impact on quality of life. The aims of this study were to compare: (i) quality of life between the general population and untreated patients with obstructive sleep apnea; and (ii) changes of quality of life among patients with obstructive sleep apnea after 2 years of positive airway pressure treatment between adherent patients and non-users. Propensity score methodologies were used in order to minimize selection bias and strengthen causal inferences. The enrolled obstructive sleep apnea subjects (n = 822) were newly diagnosed with moderate to severe obstructive sleep apnea who were starting positive airway pressure treatment, and the general population subjects (n = 742) were randomly selected Icelanders. The Short Form 12 was used to measure quality of life. Untreated patients with obstructive sleep apnea had a worse quality of life when compared with the general population. This effect remained significant after using propensity scores to select samples, balanced with regard to age, body mass index, gender, smoking, diabetes, hypertension and cardiovascular disease. We did not find significant overall differences between full and non-users of positive airway pressure in improvement of quality of life from baseline to follow-up. However, there was a trend towards more improvement in physical quality of life for positive airway pressure-adherent patients, and the most obese subjects improved their physical quality of life more. The results suggest that co-morbidities of obstructive sleep apnea, such as obesity, insomnia and daytime sleepiness, have a great effect on life qualities and need to be taken into account and addressed with additional interventions.
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| 8. |
- Bjornsdottir, Erla, et al.
(author)
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Symptoms of Insomnia among Patients with Obstructive Sleep Apnea Before and After Two Years of Positive Airway Pressure Treatment
- 2013
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In: Sleep. - : Oxford University Press (OUP). - 0161-8105 .- 1550-9109. ; 36:12, s. 1901-1909
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Journal article (peer-reviewed)abstract
- 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.
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| 9. |
- Björnsdóttir, Erla, et al.
(author)
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Insomnia in untreated sleep apnea patients compared to controls
- 2012
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In: Journal of Sleep Research. - : Wiley. - 0962-1105 .- 1365-2869. ; 21:2, s. 131-138
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Journal article (peer-reviewed)abstract
- 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.
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| 10. |
- Broström, Erika, et al.
(author)
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The prevalence of chronic airflow obstruction in three cities in the Nordic-Baltic region
- 2018
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In: Respiratory Medicine. - : Saunders Elsevier. - 0954-6111 .- 1532-3064. ; 143, s. 8-13
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Journal article (peer-reviewed)abstract
- Back ground: Chronic airflow obstruction (CAO) is the primary characteristic of Chronic obstructive pulmonary disease (COPD) but is also seen in chronic asthma. Objective: To compare the prevalence of CAO and possible risk factors between Tartu in Estonia, Reykjavik in Iceland and Uppsala in Sweden. Methods: All participants underwent spirometry testing of forced expiratory volume in 1 s (FEV1) and forced vital capacity (FVC) before and after bronchodilation. CAO was defined as post-bronchodilator FEV1/FVC below lower limit of normal. Information on respiratory diseases and smoking status, was obtained through questionnaires administered by trained interviewers. Results: 1037 men and 956 women participated in the study. The prevalence of CAO was lower in women in Tartu compared to the other centres (4.9% vs. 13.4 and 8.7% in Reykjavik and Uppsala, respectively, p = 0.002) while no difference was found for men. A similar picture was seen for the proportion of participants that had smoked 10 pack years or more which was much lower in Tartu for women than in Reykjavik and Uppsala, respectively (13.2% vs. 33.7 and 29.2%, p < 0.001). (Fig. 1). Of the participants with CAO the majority (57-67%) did not have a previous diagnosis of asthma or COPD. Conclusion: The prevalence of CAO was lower in Estonian women than in women from Iceland and Sweden. The reason for this was probably that the Estonian women had smoked less than the female participants from Iceland and Sweden. The majority of those with CAO do not have a diagnosed lung disease.
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