Showing papers by "Peretz Lavie published in 2009"

Molecular mechanisms of cardiovascular disease in OSAHS: the oxidative stress link

Abstract: Obstructive sleep apnoea/hypopnoea syndrome (OSAHS) is a highly prevalent breathing disorder in sleep that is an independent risk factor for cardiovascular morbidity and mortality. A large body of evidence, including clinical studies and cell culture and animal models utilising intermittent hypoxia, delineates the central role of oxidative stress in OSAHS as well as in conditions and comorbidities that aggregate with it. Intermittent hypoxia, the hallmark of OSAHS, is implicated in promoting the formation of reactive oxygen species (ROS) and inducing oxidative stress. The ramifications of increased ROS formation are pivotal. ROS can damage biomolecules, alter cellular functions and function as signalling molecules in physiological as well as in pathophysiological conditions. Consequently, they promote inflammation, endothelial dysfunction and cardiovascular morbidity. Oxidative stress is also a crucial component in obesity, sympathetic activation and metabolic disorders such as hypertension, dyslipidaemia and type 2 diabetes/insulin resistance, which aggregate with OSAHS. These conditions and comorbidities could result directly from the oxidative stress that is characteristic of OSAHS or could develop independently. Hence, oxidative stress represents the common underlying link in OSAHS and the conditions and comorbidities that aggregate with it.

Unexpected survival advantage in elderly people with moderate sleep apnoea.

Abstract: Sleep-disordered breathing is much more prevalent in elderly people than in middle-aged or young populations, but its clinical significance in this age group is unclear. This study investigated retrospectively the rates of all-cause mortality in elderly people (>or= 65 years) with a laboratory diagnosis of sleep apnoea, and compared their rates of mortality with that of age-, gender- and ethnicity-matched national mortality data. Survival of 611 elderly people was ascertained after a follow-up of 5.17 +/- 1.13 years. Their age was 70.4 +/- 4.8 years, body mass index 30.4 +/- 5.9 kg m(-2) and respiratory disturbance index (RDI) 28.9 +/- 20.1 events h(-1). Seventy-five (12.27%) patients died during the follow-up period. In comparison with the demographically matched cohort from the general population, the standardized mortality rate of the sleep laboratory cohort was 0.67 [95% confidence interval (CI): 0.53-0.88; chi(2) = 11.69, P 40 events h(-1) (severe apnoea) there was a significant survival advantage for the moderate group with a standardized mortality rate of 0.42 (P < 0.0002), while elderly people with no/mild apnoea tended to have lower mortality and those with severe sleep apnoea had the same mortality as the matched population cohorts. Cox regression analysis revealed that sleep latency and comorbidities but not sleep apnoea severity were associated independently with mortality. The survival advantage of elderly people with moderate sleep apnoea, combined with recent findings on the potential cardioprotective effects of chronic intermittent hypoxia, raise the possibility that apnoeas during sleep may activate adaptive pathways in the elderly.

Self-reported sleep duration--what does it mean?

Abstract: Recent years have seen a dramatic increase in the number of papers that have examined the relationship between selfreported sleep duration and health-related effects. The annual number of papers bearing the words sleep duration as part of the title increased from approximately three per year in the 1990s to more than 50 in 2008. These investigated the relationship between self-reported sleep duration and a large number of health-related conditions such as diabetes, cardiovascular morbidity, hypertension, metabolic syndrome and obesity, cancer, psychiatric disorders, neurological disorders and mortality (see a recent meta-analysis on the relationship between mortality and self-reported sleep duration and an accompanying editorial in Gallicchio and Kalesan, 2009; Grandner and Patel, 2009). Generally, both short sleep ( 8 h) were associated with detrimental health-related effects. Of note, most of these studies were not designed to investigate sleep-related effects. In many, selfreported sleep duration relied upon a single question and no information was provided on daytime sleep versus night-time sleep, nor on possible differences between weekdays and weekend sleep duration. These limitations raised the question of what is the true meaning of self-reported short or long sleep. Do they reflect actual physiological sleep amounts, or are they perhaps subjective indicators of functional states? The present issue of JSR includes two papers that investigated the relationship between self-reported sleep duration and cognitive functioning in large populations in Finland and Spain. One of them (Kronholm et al., 2009) provides interesting information on the meaning of subjective long and short sleep duration. They investigated the relationship between selfreported sleep factors such as sleep duration, insomnia, use of sleeping medications, probable sleep apnoea and fatigue and tiredness, with cognitive functioning in 5177 people older than 30 years from a cross-sectional representative sample of the adult population in Finland. Cognitive functioning was assessed objectively by verbal fluency, and encoding and retaining verbal material. In this study, short and long sleep duration and fatigue and tiredness were independent statistical predictors of low objectively measured cognitive functioning, even after controlling for health and socioeconomic factors. Sleep factors accounted for only a small proportion of the variation in the objective cognitive tests but for a much larger proportion of the variation in subjective cognitive function. Short sleep was associated with insomnia and depression, as well as with cardiovascular morbidities, while long sleep was associated with the use of neuroleptics, cerebrovascular and circulatory diseases and diabetes. Notably, a separate analysis of a subgroup of 2201 participants who did not report any illness and who also reported good, or relatively good, subjective health revealed that after adjustment for sociode

The race for the impact factor.

Abstract: Every year during the second half of June, journal editors and publishers become nervous and jittery, and perhaps even sleepless, while waiting impatiently for the publication of their journal s impact factors (IFs) for the year by Thomson Reuters (formerly Thomson Scientific). In recent years, the IF has gained a mythical influence on the prestige of journals and their published papers which has resulted in a race for the impact factor . Editors try to increase their journals IFs as much as possible and authors try to publish their papers in journals with the highest-possible IFs. This editorial was written a short time after publication of the 2008 IFs and the rush of communications by editors and publishers that followed it. The term impact factor was introduced in 1963 by Garfield and Sher (1963) for the purpose of improving the management of library journals collections. The idea was to devise an instrument that would take into consideration the importance of a journal, regardless of the number of papers it publishes. Sorting journals by IF allowed for the inclusion of many small but influential journals in bibliographic collections. Over the years, the term IF evolved gradually as a surrogate of both journal and author impact and influence, so that the mere acceptance of a paper by a high IF journal is perceived as recognition of the paper s importance. As such, it is used increasingly by academic committees, funding agencies and institutional evaluation panels in their deliberations and decisions about academic promotion and grant funding. Indeed, in some instances government funding of universities is influenced by IF considerations. The IF for a given year is calculated by dividing the total number of citations of journal papers published during a 2year period before that year by the total number of citable items published during the same 2-year period. The IF of Journal of Sleep Research (JSR) for 2008 was 3.255, as during 2006–2007 JSR published 110 citable papers that were cited 358 times in 2008. The IF of the other leading sleep journals were 4.475 for Sleep (335 papers cited 1499 times), 3.163 for Sleep Medicine (203 papers cited 642 times) and 6.143 for Sleep Medicine Reviews, that publish exclusively reviews (63 papers cited for 387 times). The growing reliance on IF for evaluating scholarly achievements has led to mounting criticism of the index and its indiscriminate use. One of the most widespread criticisms is that the distribution of citations of papers within a journal is skewed heavily and therefore cannot be represented adequately by the statistical average. Analysis of the citations distribution in the sleep journals will demonstrate this point. Forty-two of the 110 (38.1%) citable papers published during 2006–2007 in JSR were not cited or had a single citation in 2008, 24 (21.8%) were cited at least five times and five (4.5%) were cited at least 10 times (Bjorvaten et al., 2007; Fogel and Smith, 2006; Killgore et al., 2006; Russo et al., 2007; Tucker et al., 2007). Similarly, for the journal Sleep, 114 (34%) papers published in 2006–2007 were not cited in 2008 or cited only once, and 27 (8.05%) were cited at least 10 times. For Sleep Medicine Reviews, 14 (22.2%) were not cited or cited only once, 10 were cited at least 10 times (15.8%) and two (2.7%) were cited at least 20 times. It is noteworthy that a single paper published in 2006 and cited 64 times in 2008 accounted for 19.1% of Sleep Medicine Reviews IF for that year. Thus, a journal s IFs are determined mainly by a limited number of papers that are highly cited in the first 2 years after publication. Notably, even a single highly cited paper can have a disproportionately large effect on a journal s IF. Criticism has also focused on the fact that, as currently calculated, IF is biased heavily by factors irrelevant to the scientific influence of the papers. The IF is related directly to the area of research. Journals of specialized areas of science will never attain the IF of more general scientific journals. Furthermore, journals of fields in which the average number of citations per paper is traditionally low, such as mathematics, will never attain the IF of journals of fields in which the number of citations is high, such as biology or medicine. In addition, the fact that IF is based on a measurement unit of 2 years favours rapidly changing disciplines and hot subjects, and journals with a short time-lag between submission and publication. Accordingly, the three JSR papers published in 2006–2007 that had the highest number of citations in 2008 were on hot subjects of sleep research: the effect of sleep on learning, the relation of sleep duration to metabolism and the effects of sleep deprivation. A particularly troublesome problem is that the IF can be manipulated and engineered. As the IF is calculated by a simple formula comprising only two numbers – one, total citations and the second, total citable items – increasing the nominator and ⁄or decreasing the denominator can boost the IF. Editorial policies can inflate the nominator by bluntly encouraging authors to include citations from the same journal instead of citations from other journals. Although such behaviour has been discouraged by the academic and scientific community, the number of self-citations vary greatly between journals and it is not unusual to find 18–20% self citations, which adds considerably to the journal s IF. The most recent data on self-citations for the sleep journals are: JSR 5%, Sleep Medicine Reviews 4%, Sleep 10% and Sleep Medicine 8%. Impact factors can be manipulated in more subtle ways. Editorial policies to publish summaries of past publications in the journal such as A year in review -type papers, to favour papers that seem potentially highly citable regardless of their scientific quality, and to publish a large proportion of review papers over the less-cited research papers will increase the nominator of the IF formula considerably. The difference in J. Sleep Res. (2009) 18, 283–284 Editorial