Pfeiffer Christine M, Osterloh John D, Kennedy-Stephenson Jocelyn, Picciano Mary Frances, Yetley Elizabeth A, Rader Jeanne I, Johnson Clifford L
National Center for Environmental Health, Centers for Disease Control and Prevention, Atlanta, GA 30341, USA.
Clin Chem. 2008 May;54(5):801-13. doi: 10.1373/clinchem.2007.100214. Epub 2008 Mar 28.
The National Health and Nutrition Examination Survey (NHANES) has monitored total homocysteine (tHcy) concentrations in a nationally-representative sample of the US population since 1991. Until recently, however, data could not be compared across survey periods because of changes in analytical methods and specimen matrices. Such an analysis of these data could supplement current knowledge regarding whether the US folic acid fortification program has modified national plasma tHcy concentrations.
We examined tHcy data in the prefortification NHANES III survey (phase II, 1991-1994) and in 3 postfortification survey periods (1999-2000, 2001-2002, and 2003-2004). We applied method adjustment equations to the survey data based on method comparison studies of separate samples. Persons with chronic kidney disease were excluded from the analyses.
Mean plasma tHcy concentrations decreased by 8%, 9%, and 10% for adolescent, adult, and older men and by 6%, 3%, and 13% for women, respectively, from before to after fortification. Concentrations remained unchanged between the first and third postfortification survey periods. Prevalence estimates of increased plasma tHcy concentrations (>13 micromol/L) for older men and women decreased from prefortification (32% and 20%, respectively) to postfortification (14% and 5%, respectively) but remained unchanged thereafter (16% and 14%, respectively [males] and 5% and 9%, respectively [females]).
After adjusting for method changes, we quantified a prefortification to postfortification decrease in circulating tHcy concentrations of about 10% in a national sample of the US population. This change is similar to effects seen in intervention trials with folic acid and in smaller observational studies.
自1991年以来，美国国家健康与营养检查调查（NHANES）一直在监测美国具有全国代表性样本中的总同型半胱氨酸（tHcy）浓度。然而，直到最近，由于分析方法和样本基质的变化，不同调查时期的数据无法进行比较。对这些数据进行这样的分析可以补充当前关于美国叶酸强化计划是否改变了全国血浆tHcy浓度的知识。
我们检查了强化前的NHANES III调查（1991 - 1994年第二阶段）以及3个强化后的调查时期（1999 - 2000年、2001 - 2002年和2003 - 2004年）中的tHcy数据。我们根据对单独样本的方法比较研究，将方法调整方程应用于调查数据。分析中排除了患有慢性肾病的人。
从强化前到强化后，青少年男性、成年男性和老年男性的平均血浆tHcy浓度分别下降了8%、9%和10%，女性分别下降了6%、3%和13%。强化后的第一个和第三个调查时期之间浓度保持不变。老年男性和女性血浆tHcy浓度升高（>13微摩尔/升）的患病率估计值从强化前（分别为32%和20%）降至强化后（分别为14%和5%），但此后保持不变（男性分别为16%和14%，女性分别为5%和9%）。
在对方法变化进行调整后，我们在美国全国样本中量化了强化前到强化后循环tHcy浓度下降约10%。这一变化与叶酸干预试验和较小规模观察性研究中看到的效果相似。
