Key findings on women's reproductive health: the Korea Nurses' Health Study.

The Korea Nurses’ Health Study (KNHS; http://www.nhskorea.kr) is a large-scale prospective cohort study currently being conducted among female nurses in Korea. The study is based on the protocol and content of the United States Nurses’ Health Study 3 (US NHS3), adapted to account for Korea’s cultural and hospital organizational characteristics [1,2]. The purpose of the KNHS is to examine the effects of environmental, occupational, and lifestyle risk factors on the health of women of reproductive age [1]. Nurses were chosen as participants for the KNHS because their advanced understanding of disease helps ensure the validity of responses, and their commitment to study participation can help improve the follow-up rate, both of which are crucial factors in cohort studies. The participants of KNHS are female nurses of reproductive age, ranging from 20 to 45 years old at the time of baseline data collection (the first survey). A total of 20,613 nurses from hospitals across Korea participated in the initial survey. Subsequent follow-up surveys have been conducted regularly to examine factors affecting women’s health and to track their progression into middle age. The first wave of the KNHS took place between 2013 and 2015, the second wave between 2016 and 2018, and the third wave between 2019 and 2021. The fourth wave began in 2022 and is currently in its second year. Starting with the fourth wave, the participant pool has been expanded to include nurses in their 20s. An online survey system was developed to administer the KNHS. Whenever a new survey is created, participants in the baseline data collection process are sent a text message encouraging them to participate in the follow-up surveys. The nurses voluntarily participate by using a link to the questionnaire homepage provided in the text message. The main variables included in the first wave of the KNHS were demographics, weight, height, health behaviors, illness, medication, family history, pregnancy, mood, employment, occupational exposure, and subjective perception of current health. Follow-up surveys introduced additional variables alongside the content from the first wave. To date, a total of 11 surveys have been developed and completed as part of the KNHS, and a 12th survey is currently under development. Moreover, since 2014, pregnant nurses have had the opportunity to answer separate survey questions focusing on early pregnancy and post-pregnancy [1]. In 2016, during the first year of the second wave, 2,000 nurses who had participated in the baseline survey underwent anthropometric measurements (e.g., waist circumference), had their blood Issues and Perspectives