Royle Pamela, Kandala Ngianga-Bakwin, Barnard Katharine, Waugh Norman
Division of Health Sciences, Warwick Medical School, University of Warwick, CV4 7AL, Coventry, UK.
Syst Rev. 2013 Sep 12;2:74. doi: 10.1186/2046-4053-2-74.
Systematic reviews are important for informing clinical practice and health policy. The aim of this study was to examine the bibliometrics of systematic reviews and to determine the amount of variance in citations predicted by the journal impact factor (JIF) alone and combined with several other characteristics.
We conducted a bibliometric analysis of 1,261 systematic reviews published in 2008 and the citations to them in the Scopus database from 2008 to June 2012. Potential predictors of the citation impact of the reviews were examined using descriptive, univariate and multiple regression analysis.
The mean number of citations per review over four years was 26.5 (SD ± 29.9) or 6.6 citations per review per year. The mean JIF of the journals in which the reviews were published was 4.3 (SD ± 4.2). We found that 17% of the reviews accounted for 50% of the total citations and 1.6% of the reviews were not cited. The number of authors was correlated with the number of citations (r = 0.215, P < 0.001). Higher numbers of citations were associated with the following characteristics: first author from the United States (36.5 citations), an ICD-10 chapter heading of Neoplasms (31.8 citations), type of intervention classified as Investigation, Diagnostics or Screening (34.7 citations) and having an international collaboration (32.1 citations). The JIF alone explained more than half of the variation in citations (R(2) = 0.59) in univariate analysis. Adjusting for both JIF and type of intervention increased the R2 value to 0.81. Fourteen percent of reviews published in the top quartile of JIFs (≥ 5.16) received citations in the bottom quartile (eight or fewer), whereas 9% of reviews published in the lowest JIF quartile (≤ 2.06) received citations in the top quartile (34 or more). Six percent of reviews in journals with no JIF were also in the first quartile of citations.
The JIF predicted over half of the variation in citations to the systematic reviews. However, the distribution of citations was markedly skewed. Some reviews in journals with low JIFs were well-cited and others in higher JIF journals received relatively few citations; hence the JIF did not accurately represent the number of citations to individual systematic reviews.
系统评价对于指导临床实践和卫生政策具有重要意义。本研究旨在考察系统评价的文献计量学特征，并确定仅由期刊影响因子（JIF）以及结合其他几个特征所预测的被引频次的变异量。
我们对2008年发表的1261篇系统评价及其在Scopus数据库中2008年至2012年6月期间的被引情况进行了文献计量分析。使用描述性、单变量和多元回归分析来考察这些评价的被引影响的潜在预测因素。
四年间每篇评价的平均被引次数为26.5次（标准差±29.9），即每年每篇评价的平均被引次数为6.6次。发表这些评价的期刊的平均JIF为4.3（标准差±4.2）。我们发现17%的评价占总被引次数的50%，1.6%的评价未被引用。作者数量与被引次数相关（r = 0.215，P < 0.001）。较高的被引次数与以下特征相关：第一作者来自美国（36.5次被引）、ICD - 10肿瘤章节标题（31.8次被引）、干预类型归类为调查、诊断或筛查（34.7次被引）以及有国际合作（32.1次被引）。在单变量分析中，仅JIF就解释了超过一半的被引变异（R² = 0.59）。同时调整JIF和干预类型后，R²值增加到0.81。在JIF处于前四分位数（≥5.16）的期刊上发表的评价中有14%在被引次数的后四分位数（8次或更少）中被引用，而在JIF最低四分位数（≤2.06）的期刊上发表的评价中有9%在被引次数的前四分位数（34次或更多）中被引用。在没有JIF的期刊上发表的评价中有6%也处于被引次数的第一四分位数。
JIF预测了系统评价被引次数变异的一半以上。然而，被引次数的分布明显偏态。一些在JIF较低的期刊上发表的评价被大量引用，而其他在JIF较高的期刊上发表的评价被引用相对较少；因此，JIF并不能准确反映单个系统评价的被引次数。
