Lars E. Laugsand

Shift work and vascular events: systematic review and meta-analysis

Objective To synthesise the association of shift work with major vascular events as reported in the literature. Data sources Systematic searches of major bibliographic databases, contact with experts in the field, and review of reference lists of primary articles, review papers, and guidelines. Study selection Observational studies that reported risk ratios for vascular morbidity, vascular mortality, or all cause mortality in relation to shift work were included; control groups could be non-shift (“day”) workers or the general population. Data extraction Study quality was assessed with the Downs and Black scale for observational studies. The three primary outcomes were myocardial infarction, ischaemic stroke, and any coronary event. Heterogeneity was measured with the I2 statistic and computed random effects models. Results 34 studies in 2 011 935 people were identified. Shift work was associated with myocardial infarction (risk ratio 1.23, 95% confidence interval 1.15 to 1.31; I2=0) and ischaemic stroke (1.05, 1.01 to 1.09; I2=0). Coronary events were also increased (risk ratio 1.24, 1.10 to 1.39), albeit with significant heterogeneity across studies (I2=85%). Pooled risk ratios were significant for both unadjusted analyses and analyses adjusted for risk factors. All shift work schedules with the exception of evening shifts were associated with a statistically higher risk of coronary events. Shift work was not associated with increased rates of mortality (whether vascular cause specific or overall). Presence or absence of adjustment for smoking and socioeconomic status was not a source of heterogeneity in the primary studies. 6598 myocardial infarctions, 17 359 coronary events, and 1854 ischaemic strokes occurred. On the basis of the Canadian prevalence of shift work of 32.8%, the population attributable risks related to shift work were 7.0% for myocardial infarction, 7.3% for all coronary events, and 1.6% for ischaemic stroke. Conclusions Shift work is associated with vascular events, which may have implications for public policy and occupational medicine.

Insomnia and the Risk of Acute Myocardial Infarction A Population Study

Background— Few prospective studies have investigated insomnia in relation to risk for coronary heart disease. We assessed insomnia symptoms and risk of acute myocardial infarction (AMI) in a large, population-based study. Methods and Results— A total of 52 610 men and women were followed up for a first AMI, and 2368 incident AMIs occurred during 11.4 years of follow-up, either identified at hospitals or by the National Cause of Death Registry. In our analyses, we adjusted for age, sex, marital status, education, shift work, blood pressure, lipids, diabetes mellitus, body mass index, physical activity, smoking, and alcohol consumption. Difficulties initiating and maintaining sleep and having a feeling of nonrestorative sleep were associated with a moderate increase in AMI risk. The multiadjusted hazard ratios for AMI were 1.45 (95% confidence interval 1.18–1.80) for people with difficulties initiating sleep almost every night, 1.30 (1.01–1.68) for those with difficulties maintaining sleep almost every night, and 1.27 (1.03–1.57) for those with a feeling of nonrestorative sleep more than once a week compared with people who never experienced these sleep difficulties. When we combined the symptoms, a dose-dependent association was seen between the number of insomnia symptoms and AMI risk (P for trend 0.003). Alternative multivariable models and different sensitivity analyses suggest that the results were robust, especially concerning difficulties initiating sleep. Conclusions— Insomnia is associated with a moderately increased risk for AMI.

Insomnia and the risk of incident heart failure: a population study

AIMS Insomnia is highly prevalent among heart failure patients, but only a few small studies have investigated insomnia symptoms and risk of heart failure. We aimed to assess the prospective association between self-reported insomnia symptoms and the risk of incident heart failure in a large Norwegian cohort. METHODS AND RESULTS Baseline data on insomnia symptoms, including difficulty initiating sleep, difficulty maintaining sleep and having non-restorative sleep, socio-demographic variables, and health status, including established cardiovascular risk factors, were collected from 54 279 men and women 20-89 years of age who participated in the Nord-Trøndelag Health study (HUNT) between 1995 and 1997 and were free from known heart failure at baseline. The cohort was followed for incident heart failure from baseline through 2008. We used Cox proportional hazard models to assess the association of baseline insomnia symptoms with the risk of heart failure. A total of 1412 cases of heart failure occurred during a mean follow-up of 11.3 years (SD = 2.9 years), either identified at hospitals or by the National Cause of Death Registry. There was a dose-dependent association between the number of insomnia symptoms and risk of heart failure. The multi-adjusted hazard ratios were 0.96 (0.57-1.61), 1.35 (0.72-2.50), and 4.53 (1.99-10.31) for people with one, two, and three insomnia symptoms, compared with people with none of the symptoms (P for trend 0.021). CONCLUSIONS Insomnia is associated with an increased risk of incident heart failure. If our results are confirmed by others and causation is proved, evaluation of insomnia symptoms might have consequences for cardiovascular prevention.

Insomnia and Endothelial Function – The HUNT 3 Fitness Study

Background Insomnia is associated with increased risk of coronary heart disease (CHD), but the underlying mechanisms are not understood. To our knowledge, no previous studies have examined insomnia in relation to endothelial function, an indicator of preclinical atherosclerosis. Our aim was to assess the association of insomnia with endothelial function in a large population based study of healthy individuals. Methods A total of 4 739 participants free from known cardiovascular or pulmonary diseases, cancer, and sarcoidosis, and who were not using antihypertensive medication were included in the study. They reported how often they had experienced difficulties falling asleep at night, repeated awakenings during the night, early awakenings without being able to go back to sleep, and daytime sleepiness. Endothelial function was measured by flow mediated dilation (FMD) derived from the brachial artery. Results We found no consistent association between the insomnia symptoms and endothelial function in multiadjusted models, but individual insomnia symptoms may be related to endothelial function. Among women who reported early awakenings, endothelial function may be lower than in women without this symptom (p = 0.03). Conclusions This study provided no evidence that endothelial function, an early indicator of atherosclerosis, is an important linking factor between insomnia and CHD. Further studies are needed to explore the complex interrelation between sleep and cardiovascular pathology.

Symptoms of anxiety and depression and risk of acute myocardial infarction: the HUNT 2 study

Aims The nature of the association of depression and anxiety with risk for acute myocardial infarction (AMI) remains unclear. We aimed to study the prospective association of single and recurrent self-reported symptoms of anxiety and depression with a risk of AMI in a large Norwegian population based cohort. Methods and results In the second wave of the Nord-Trøndelag Health Study (HUNT2, 1995–97) baseline data on anxiety and depression symptoms, sociodemographic variables, health status including cardiovascular risk factors and common chronic disorders were registered for 57 953 adult men and women free of cardiovascular disease. The cohort was followed up during a mean (SD) 11.4 (2.9) years for a first AMI from baseline through 2008. A total of 2111 incident AMIs occurred, either identified at hospitals or by the National Cause of Death Registry. The multi-adjusted hazard ratios were 1.31 (95% CI 1.03–1.66) for symptoms of depression and 1.25 (CI 0.99–1.57) for anxiety. Two episodes of mixed symptoms of anxiety and depression (MSAD), reported 10 years apart, increased the risk for AMI by 52% (11–108%). After exclusion of the first 5 years of follow-up, the association of depression symptoms with AMI risk was attenuated. Relative risk for AMI with anxiety symptoms and MSAD weakened when participants with chronic disorders were excluded. Conclusion Self-reported symptoms of depression and anxiety, especially if recurrent, were moderately associated with the risk of incident AMI. We had some indications that these associations might partly reflect reverse causation or confounding from common chronic diseases.

Insomnia and high-sensitivity C-reactive protein: the HUNT study, Norway.

Objective To explore the hypothesis that insomnia may increase the risk of coronary heart disease through inflammatory mechanisms. Methods The association of high-sensitivity C-reactive protein (hsCRP) with self-reported symptoms of insomnia was examined. Participants were 8547 men and nonpregnant women who answered one or more insomnia-related questions and who had available hsCRP measurements in the Nord-Trøndelag Health Study. In multivariable linear regression analyses of the logarithm of hsCRP, we adjusted for established cardiovascular risk factors, psychosocial distress, chronic pain, and chronic somatic disorders. Results Among men, difficulties initiating sleep and nonrestorative sleep were associated with increasing hsCRP levels after adjusting for age (B = 0.07, 95% confidence interval [CI] = 0.01–0.14, p for trend = .02 and B = 0.09, 95% CI = 0.02–0.15, p for trend = .006), but after multivariable adjustment, the associations were attenuated (B = 0.03, 95% CI = −0.03 to 0.09, p for trend = .30 and B = 0.06, 95% CI = −0.00 to 0.12, p for trend = .05). HsCRP was not associated with other insomnia-related symptoms. In women, there was no evidence for any association of symptoms of insomnia with hsCRP levels. Results indicated sex differences in the association between sleep characteristics and CRP (difficulties maintaining sleep, p interaction = .018; cumulative number of symptoms of insomnia, p interaction = .014; and symptoms of insomnia influencing work performance, p interaction = .039). Conclusions There were no consistent associations between symptoms of insomnia and hsCRP levels. Our results do not support the hypothesis that inflammation, as reflected by elevated levels of hsCRP, is an important factor linking insomnia to coronary heart disease. Abbreviations CHD = coronary heart disease hsCRP = high-sensitivity C-reactive protein BMI = body mass index HDL = high-density lipoprotein

Symptoms of anxiety and depression and risk of heart failure: the HUNT Study

Symptoms of anxiety and depression often co‐exist with cardiovascular disease, yet little is known about the prospective risk for heart failure (HF) in people with symptoms of depression and anxiety. We aimed to study these prospective associations using self‐reported symptoms of anxiety, depression, and mixed symptoms of anxiety and depression (MSAD) in a large population sample.

Insomnia symptoms and risk for unintentional fatal injuries-the HUNT Study

STUDY OBJECTIVES To assess the association between insomnia symptoms and risk of fatal unintentional injuries. DESIGN Population-based prospective cohort study with a mean follow-up of 14 y, linking health survey data with information on insomnia symptoms to the National Cause of Death Registry. SETTING Nord-Trøndelag County, Norway. PARTICIPANTS A total of 54,399 men and women 20-89 y of age who participated in the Nord-Trøndelag Health Study between 1995 and 1997. INTERVENTIONS N/A. MEASUREMENTS AND RESULTS There were 277 unintentional fatal injuries, including 57 fatal motor vehicle injuries during follow-up. There was a dose-dependent association between the number of insomnia symptoms and risk of unintentional fatal injuries (P for trend 0.001) and fatal motor vehicle injuries (P for trend 0.023), respectively. The proportion of unintentional fatal injuries cases that could have been prevented in the absence of difficulties initiating sleep, difficulties maintaining sleep, and having a feeling of nonrestorative sleep were 8%, 9%, and 8%, respectively. The corresponding estimates for motor vehicle injuries were 34%, 11%, and 10%. CONCLUSION Insomnia is a major contributor to both unintentional fatal injuries in general as well as fatal motor vehicle injuries. Increasing public health awareness about insomnia and identifying persons with insomnia may be important in preventing unintentional fatal injuries.

Insomnia and the Risk of Acute Myocardial Infarction

Background— Few prospective studies have investigated insomnia in relation to risk for coronary heart disease. We assessed insomnia symptoms and risk of acute myocardial infarction (AMI) in a large, population-based study. Methods and Results— A total of 52 610 men and women were followed up for a first AMI, and 2368 incident AMIs occurred during 11.4 years of follow-up, either identified at hospitals or by the National Cause of Death Registry. In our analyses, we adjusted for age, sex, marital status, education, shift work, blood pressure, lipids, diabetes mellitus, body mass index, physical activity, smoking, and alcohol consumption. Difficulties initiating and maintaining sleep and having a feeling of nonrestorative sleep were associated with a moderate increase in AMI risk. The multiadjusted hazard ratios for AMI were 1.45 (95% confidence interval 1.18–1.80) for people with difficulties initiating sleep almost every night, 1.30 (1.01–1.68) for those with difficulties maintaining sleep almost every night, and 1.27 (1.03–1.57) for those with a feeling of nonrestorative sleep more than once a week compared with people who never experienced these sleep difficulties. When we combined the symptoms, a dose-dependent association was seen between the number of insomnia symptoms and AMI risk (P for trend 0.003). Alternative multivariable models and different sensitivity analyses suggest that the results were robust, especially concerning difficulties initiating sleep. Conclusions— Insomnia is associated with a moderately increased risk for AMI.

Alcohol consumption is associated with a lower incidence of acute myocardial infarction: results from a large prospective population‐based study in Norway

Compelling evidence suggests that light‐to‐moderate alcohol consumption is associated with a reduced risk of acute myocardial infarction (AMI), but several issues from previous studies remain to be addressed. The aim of this study was to investigate some of these key issues related to the association between alcohol consumption and AMI risk, including the strength and shape of the association in a low‐drinking setting, the roles of quantity, frequency and beverage type, the importance of confounding by medical and psychiatric conditions, and the lack of prospective data on previous drinking.