National Health and Nutrition Examination Survey (NHANES), 1999-2000

The National Health and Nutrition Examination Surveys (NHANES) is a program of studies designed to assess the health and nutritional status of adults and children in the United States. The NHANES combines personal interviews and physical examinations, which focus on different population groups or health topics. These surveys have been conducted by the National Center for Health Statistics (NCHS) on a periodic basis from 1971 to 1994. In 1999 the NHANES became a continuous program with a changing focus on a variety of health and nutrition measurements which were designed to meet current and emerging concerns. The surveys examine a nationally representative sample of approximately 5,000 persons each year. These persons are located in counties across the United States, 15 of which are visited each year. The 1999-2000 NHANES contains data for 9,965 individuals (and MEC examined sample size of 9,282) of all ages. Many questions that were asked in NHANES II, 1976-1980, Hispanic HANES 1982-1984, and NHANES III, 1988-1994, were combined with new questions in the NHANES 1999-2000.
The 1999-2000 NHANES collected data on the prevalence of selected chronic conditions and diseases in the population and estimates for previously undiagnosed conditions, as well as those known to and reported by respondents. Risk factors, those aspects of a person's lifestyle, constitution, heredity, or environment that may increase the chances of developing a certain disease or condition, were examined. Data on smoking, alcohol consumption, sexual practices, drug use, physical fitness and activity, weight, and dietary intake were collected. Information on certain aspects of reproductive health, such as use of oral contraceptives and breastfeeding practices, were also collected. The interview includes demographic, socioeconomic, dietary, and health-related questions. The examination component consists of medical, dental, and physiological measurements, as well as laboratory tests. Demographic data file variables are grouped into three broad categories: (1) Status Variables: Provide core information on the survey participant. Examples of the core variables include interview status, examination status, and sequence number. (Sequence number is a unique ID assigned to each sample person and is required to match the information on this demographic file to the rest of the NHANES 1999-2000 data). (2) Recoded Demographic Variables: The variables include age (age in months for persons through age 19 years, 11 months; age in years for 1-84 year olds, and a top-coded age group of 85+ years), gender, a race/ethnicity variable, an education variable (high school, and more than high school education), country of birth (United States, Mexico, or other foreign born), and pregnancy status variable. Some of the groupings were made due to limited sample sizes for the two-year dataset. (3) Interview and Examination Sample Weight Variables: Sample weights are available for analyzing NHANES 1999-2000 data. For a complete listing of survey contents for all years of the NHANES see the document -- Survey Content -- NHANES 1999-2010.

国家健康与营养检查调查（National Health and Nutrition Examination Surveys, NHANES）是一项旨在评估美国成人及儿童健康与营养状况的研究项目。NHANES融合个人访谈与体格检查两类调研方式，研究重点覆盖不同人群亚组或健康主题。该调查由美国国家卫生统计中心（National Center for Health Statistics, NCHS）于1971年至1994年间周期性开展。1999年起，NHANES转为持续性调查项目，其研究重点随当前及新出现的健康与营养关切问题不断调整。每年的调查会选取约5000名具有全国代表性的样本对象，这些对象分布于美国各地的县份，项目每年会选取其中15个县开展实地走访。1999-2000周期的NHANES包含9965名各年龄段个体的调研数据（其中接受医学检查中心（Medical Examination Center, MEC）检查的样本量为9282）。NHANES II（1976-1980年）、西班牙裔NHANES（1982-1984年）及NHANES III（1988-1994年）中的大量调研问题，与1999-2000周期NHANES新增的问题进行了整合。

1999-2000周期的NHANES收集了人群中特定慢性疾病与病症的患病率数据，以及此前未被诊断的病症、受访者已知并上报的病症的相关估计值。调研同时覆盖了风险因素——即可能增加个体罹患特定疾病或病症概率的生活方式、体质、遗传或环境相关因素。调查收集了吸烟、饮酒、性行为情况、药物使用、体能与活动水平、体重及膳食摄入相关数据，此外还收集了生殖健康相关信息，如口服避孕药使用情况与母乳喂养行为。访谈环节涵盖人口统计学、社会经济、膳食及健康相关问题；检查环节则包含医学、牙科与生理学测量，以及实验室检测。

人口统计学数据文件的变量可分为三大类别：
1. 状态变量：用于提供调研参与者的核心信息，核心变量示例包括访谈状态、检查状态及序列编号（序列编号为每位样本对象分配的唯一标识符，用于将此人口统计学文件中的信息与1999-2000周期NHANES的其余数据进行匹配关联）。
2. 重新编码人口统计学变量：此类变量包括年龄（19岁11个月及以下对象的年龄以月为单位，1-84岁对象的年龄以年为单位，85岁及以上年龄组采用封顶编码）、性别、种族/族裔变量、教育程度变量（高中及以上学历）、出生国家（美国、墨西哥或其他外国出生）及妊娠状态变量。部分分组设置的原因在于两年期数据集的样本量有限。
3. 访谈与检查样本权重变量：样本权重可用于分析1999-2000周期的NHANES数据。如需查看NHANES所有年份的完整调研内容清单，请参阅文档——《调查内容——NHANES 1999-2010》。