关于硒元素(Selenium,Se)的生物学效应,研究得最多的恐怕是其抗癌作用,但学术界对此历来就存有争议 。 尽管如此,人们还是相信摄硒能够降低癌症风险。许多食物中都富含硒,如巴西坚果(brazil nuts,如下图)。然而,最近的一项随机控制临床试验( RCCT,randomized controlled clinical trials)研 究表明,硒对非黑素类的皮肤癌、前列腺癌都无防范作用。研究结果发表在 Cochrane Database Syst. Rev (2011年,第5期, DOI: 10.1002/14651858.CD005195 )上。主持这项研究的是来自德国柏林THR学院( Institute for Transdisciplinary Health Research )的 Gabriele Dennert 教授。 该研究组搜索了摄硒效应的临床研究文献,发现了49项预期的观察研究( observational studies )和6项随机控制临床试验。其中,观察研究表明,高硒摄入可以防范癌症,但RCCT研究却表明无此明显作用。另外还有迹象表明,如果摄硒时程过长,会造成有害效应。 Russo MW, Murray SC, Wurzelmann JI, Woosley JT, Sandler RS (1997). "Plasma selenium levels and the risk of colorectal adenomas". Nutrition and Cancer 28 (2): 125–9. doi : 10.1080/01635589709514563 . PMID 9290116 . Knekt P, Marniemi J, Teppo L, Helivaara M, Aromaa A (15 November 1998). "Is low selenium status a risk factor for lung cancer?" . American Journal of Epidemiology 148 (10): 975–82. PMID 9829869 . http://aje.oxfordjournals.org/cgi/pmidlookup?view=longpmid=9829869 . Young KJ, Lee PN (1999). "Intervention studies on cancer". European Journal of Cancer Prevention 8 (2): 91–103. doi : 10.1097/00008469-199904000-00003 . PMID 10335455 . Burguera JL, Burguera M, Gallignani M, Alarcón OM, Burguera JA (1990). "Blood serum selenium in the province of Mérida, Venezuela, related to sex, cancer incidence and soil selenium content" (Free full text). Journal of Trace Elements and Electrolytes in Health and Disease 4 (2): 73–7. PMID 2136228 . Clark LC, Combs GF, Turnbull BW, et al. (1996). "Effects of selenium supplementation for cancer prevention in patients with carcinoma of the skin. A randomized controlled trial. Nutritional Prevention of Cancer Study Group". JAMA 276 (24): 1957–63. doi : 10.1001/jama.276.24.1957 . PMID 8971064 . Lippman SM, Klein EA, Goodman PJ, et al. (2009). "Effect of selenium and vitamin E on risk of prostate cancer and other cancers: the Selenium and Vitamin E Cancer Prevention Trial (SELECT)" (Free full text). JAMA 301 (1): 39–51. doi : 10.1001/jama.2008.864 . PMID 19066370 . "Chemoprevention Database" . http://www.inra.fr/reseau-nacre/sci-memb/corpet/indexan.html . Retrieved 2009-05-05 . Garland M, Morris JS, Stampfer MJ, et al. (1995). "Prospective study of toenail selenium levels and cancer among women". Journal of the National Cancer Institute 87 (7): 497–505. doi : 10.1093/jnci/87.7.497 . PMID 7707436 . Hercberg S, Galan P, Preziosi P, et al. (1998). "Background and rationale behind the SU.VI.MAX Study, a prevention trial using nutritional doses of a combination of antioxidant vitamins and minerals to reduce cardiovascular diseases and cancers. Supplementation en Vitamines et Minéraux Antioxydants Study" (Free full text). International Journal for Vitamin and Nutrition Research 68 (1): 3–20. PMID 9503043 . http://www.nlm.nih.gov/medlineplus/antioxidants.html . Hercberg S, Galan P, Preziosi P, et al. (2004). "The SU.VI.MAX Study: a randomized, placebo-controlled trial of the health effects of antioxidant vitamins and minerals" (Free full text). Archives of Internal Medicine 164 (21): 2335–42. doi : 10.1001/archinte.164.21.2335 . PMID 15557412 . "Selenium and Chemotherapy - Nutrition Health" . http://nutrition-health.info/index.php/Selenium_and_Chemotherapeutic_Drugs . "Selenium Cancer" . http://nutrition-health.info/index.php/Selenium_Cancer_1 . Nilsonne G, Sun X, Nystrm C, et al. (2006). "Selenite induces apoptosis in sarcomatoid malignant mesothelioma cells through oxidative stress". Free Radical Biology Medicine 41 (6): 874–85. doi : 10.1016/j.freeradbiomed.2006.04.031 . PMID 16934670 . Tsavachidou D, McDonnell TJ, Wen S, et al. (2009). "Selenium and vitamin E: cell type- and intervention-specific tissue effects in prostate cancer" . Journal of the National Cancer Institute 101 (5): 306–20. doi : 10.1093/jnci/djn512 . PMC 2734116 . PMID 19244175 . http://www.pubmedcentral.nih.gov/articlerender.fcgi?tool=pmcentrezartid=2734116 . Klein EA (2009). "Selenium and vitamin E: interesting biology and dashed hope". Journal of the National Cancer Institute 101 (5): 283–5. doi : 10.1093/jnci/djp009 . PMID 19244172 .
暂且先把以前的文章转来撑撑门面。 2008/11/17 20:48:30 晚上有牛同学的婚宴,五点半,食堂四楼。五点零七的时候刚要收拾东东走人,老板突然破门而入,头对头临床试验是怎么回事,帮我查查告诉我。 时间紧任务重啊! 网上搜刮了一下,好像没有定义,只能从提及的只言片语里寻找、推敲、归纳总结。在一篇介绍药物洗脱支架临床研究的文章里找到这样一段话,算是中文网页里说的比较明确的了,所谓直接比较研究即头对头(Head to Head)研究,又可分为优效性研究和等效/ 非劣效性研究;间接比较包括随机临床试验的亚组分析比较和注册临床研究的比较。( http://www.ccheart.com.cn/doctor/news/3702.html 《从循证医学角度看药物洗脱支架的临床试》)如此看来,头对头研究的目的主要是解决一般的临床试验中用亚组分析解决的问题,但解决的方法更直接按照特定的试验目的设计单独的临床试验,给药物的某些特殊特性的相关问题(如,治疗高血压的药物对靶器官的保护,干扰素在肝炎治疗中对不同基因型患者的疗效差别等)以直接明了的回答,也即针对药物(一般是疗效已经确定的药物)的特性设计完成单独的临床试验,进行临床研究,其目的已经不是研究药物是否有效,而是对药物疗效或安全性进行更加细致的研究,一般要求试验组与对照组的均衡性、可比性更强,使研究目的所针对的问题能够在尽可能单纯的条件下进行比较。《JIKEI HEART试验结果探析---联合抗高血压药物治疗》( http://www.bhli.org.cn/show.aspx?cid=10id=255 )中提到后期的临床试验大部分是头对头的试验,所谓头对头(Head to Head)研究即直接比较研究,又分为优效性研究和等效/非劣效性研究。试验不再简单讨论降压本身是否有益,而是要观察不同类别的降压药物在获得相同降压幅度的基础上,是否对靶器官有额外的保护作用。这样的临床试验常常需尽可能减小两组间血压变化的差别,使血压差异对结果的影响降低。由于降压治疗的临床获益主要来源于血压降低的幅度,因此,即使仅仅是平均2 mmHg~3 mmHg的血压差别的临床获益,已足以稀释了来自于药物本身的有益影响。这个例子就举得很好。 正当觉得已经比较明确的时候,又发现这样一个帖子,《何谓头对头试验》( http://www.med66.com/html/ziliao/yixue/7/cc078c6cc4d42df845e7c0e6782d9e29.htm )说就是单挑的意思, 呵呵, 比如两个药的效果的单挑。这下子还真有点蒙了,到底什么是头对头试验?看来只能找找英文网页了。于是乎首先想到去FDA的网站里搜搜看。 《The Healing Power of Placebos》( http://www.fda.gov/fdac/features/2000/100_heal.html )中提到:FDA doesn't require that a drug study include a placebo control group, DeLap says, only that its design be capable of establishing a drug's safety and effectiveness. Non-placebo types of drug studies include head-to-head studies, which compare the experimental drug to an existing treatment, and historically controlled studies, which compare the new drug's effects with information gathered in the past about the expected progression of a medical condition. 非常好,终于有比较确定的说法了,至少可以看出,头对头试验肯定是非安慰剂对照的试验,它是以临床上已经使用的治疗药物或治疗方法为对照的临床试验。 《Ottawa Panel evidence-based clinical practice guidelines for therapeutic exercises in the management of rheumatoid arthritis in adults.》( http://www.guideline.gov/summary/summary.aspx?ss=15doc_id=6264nbr=4019 )来自National Guideline Clearinghouse的一篇文章,其中提到Head-to-head studies (that is, the comparison of 2 active interventions, such as therapeutic exercises versus transcutaneous electrical nerve stimulation) were generally excluded in these recommendations. 由此可见所谓头对头研究就仅仅是指两种已经确认有效的治疗方法的比较。哎,没想到是这样,不是很甘心所以在一篇老外的帖子里提了下这个问题,等回信了再来补上最新消息吧。 头对头研究暂且告一段落。
最近在打击非法药品广告中, 有几位名人中了彩. 这几位公众人物是否做人厚道, 不是本来想关注的问题. 民众和舆论自有公道. 问题是这样的宣传, 商家为什么屡禁不止? 利益熏心是一方面原因, 另一方面是这种所谓名人效应和广告夸大宣传,还真管用. 老百姓信这一套. 就象某一治癌产品, 挂中科院技术名义, 整天在媒体做广告,夸大宣传,欺骗老百姓。 内部人员还很得意地说,如果不这样宣传,就没有人信,没有人买。这和抢钱骗钱有何区别? 中国是营养保健品泛滥成灾的国家。 有许多产品被夸大宣传。 吹得神乎其神。广告方面的规范和处罚很轻。那么在国外保健品,是否也有很多人信呢? 当然也是。 因为保健品的销售比药品松好多。国外的宣传攻势也很厉害。宣传多了,人们就信了。 商家也就等着数钱就是了。 关于营养保健品和复方维生素的功效, 在消费者心目中似乎是比较相信的, 不然不会卖得这么火爆. 这里有许多舆论宣传的功劳. 但医药界并非十分确信媒体造势所选宣传的诸多好处. 从循证医学的角度, 必须要有可靠的临床试验数据, 才能标上某种药效功能. 不然只能说未经证实和批准的疗效或个案报道. 最近纽约时报有一篇文章,引用了美国医学会刚发表的文章, 涉及银杏产品。 由于替代医学越来越越被人们所接受, 那么营养保健品或部分天然产物的临床疗效自然也受到业内的关注. 最新的数据是来自对银杏叶,这是在市场上流行的,广泛用于改善记忆和其他认知功能的天然产物或营养保健品。 研究者得到美国联邦政府资助,对3000多名年龄在72-96岁的老人进行随机分布,分别采取安慰剂或120毫克的银杏抽提物做成的制剂,一天服用两次。然后进行长期观察。 研究开始时,这些受试验的老人在服用安慰剂或银杏制剂时并没有患有痴呆症。所有受试验的人都经历中位数为6年的观察。 结果发现,那些服用银杏的人在记忆,语言,注意力和认知功能等测量指标上表现得并不比那些服用安慰剂的人更好。该成果发表在本周的美国医学会JAMA 杂志上,一个更早所完成的临床研究分析还发现,银杏没有减少人们患老年痴呆症的风险。 正如今年早些时候,纽约时报专栏曾经指出,在过去几年。有大型临床研究表明,某些维生素药片和其他营养补品不改善健康方面的关键参数和结果。 一位研究过这些数据和结果的医生告诉纽约时报记者说,我感到疑惑,为何市民普遍忽略了这种十分规范的临床试验熟结果, 公众对服用维生素和营养保健品的信任度,尽管没有得到现有科学数据的支持,但是仍然无法扭转局面,义无反顾地继续服用在专业人士看来是无功效的产品。实在让人费解。政府或许没有什么可做的,因为即使是安慰剂效应,只要没有安全隐患,政府无权禁止营养保健品的畅销,这全看商家的宣传本事。 Ginkgo biloba for Preventing Cognitive Decline in Older Adults A Randomized Trial JAMA. 2009;302(24):2663-2670. ABSTRACT Context The herbal product Ginkgo biloba is taken frequently with the intention of improving cognitive health in aging. However, evidence from adequately powered clinical trials is lacking regarding its effect on long-term cognitive functioning. Objective To determine whether G biloba slows the rates of global or domain-specific cognitive decline in older adults. Design, Setting, and Participants The Ginkgo Evaluation of Memory (GEM) study, a randomized, double-blind, placebo-controlled clinical trial of 3069 community-dwelling participants aged 72 to 96 years, conducted in 6 academic medical centers in the United States between 2000 and 2008, with a median follow-up of 6.1 years. Intervention Twice-daily dose of 120-mg extract of G biloba (n=1545) or identical-appearing placebo (n=1524). Main Outcome Measures Rates of change over time in the Modified Mini-Mental State Examination (3MSE), in the cognitive subscale of the Alzheimer Disease Assessment Scale (ADAS-Cog), and in neuropsychological domains of memory, attention, visual-spatial construction, language, and executive functions, based on sums of z scores of individual tests. Results Annual rates of decline in z scores did not differ between G biloba and placebo groups in any domains, including memory (0.043; 95% confidence interval , 0.034-0.051 vs 0.041; 95% CI, 0.032-0.050), attention (0.043; 95% CI, 0.037-0.050 vs 0.048; 95% CI, 0.041-0.054), visuospatial abilities (0.107; 95% CI, 0.097-0.117 vs 0.118; 95% CI, 0.108-0.128), language (0.045; 95% CI, 0.037-0.054 vs 0.041; 95% CI, 0.033-0.048), and executive functions (0.092; 95% CI, 0.086-0.099 vs 0.089; 95% CI, 0.082-0.096). For the 3MSE and ADAS-Cog, rates of change varied by baseline cognitive status (mild cognitive impairment), but there were no differences in rates of change between treatment groups (for 3MSE, P =.71; for ADAS-Cog, P =.97). There was no significant effect modification of treatment on rate of decline by age, sex, race, education, APOE*E4 allele, or baseline mild cognitive impairment ( P .05). Conclusion Compared with placebo, the use of G biloba, 120 mg twice daily, did not result in less cognitive decline in older adults with normal cognition or with mild cognitive impairment. Trial Registration clinicaltrials.gov Identifier: NCT00010803