{"id":1845,"date":"2020-11-17T14:57:37","date_gmt":"2020-11-17T14:57:37","guid":{"rendered":"http:\/\/kostforskning.dk\/?page_id=1845"},"modified":"2026-01-23T12:17:47","modified_gmt":"2026-01-23T12:17:47","slug":"den-danske-sygeplejerskekohorte-2","status":"publish","type":"page","link":"https:\/\/kostforskning.com\/en\/kohorter\/den-danske-sygeplejerskekohorte-2\/","title":{"rendered":"Den Danske Sygeplejerskekohorte"},"content":{"rendered":"

Historical Background<\/strong><\/p>\n

The Danish Nurse Cohort was established in 1993. The original purpose was to investigate the benefits and risks of hormone use during menopause in a prospective cohort design.<\/p>\n

Consequences of Women’s Use of Hormone Replacement Therapy (HRT)<\/strong><\/p>\n

The primary reason for establishing the Danish Nurse Cohort was to investigate the long-term consequences of women\u2019s use of hormone replacement therapy (HRT). A number of studies, mostly American, had shown in the 1980s that HRT could reduce hip fractures by about 40% and reduce the incidence of cardiovascular diseases by 40-50%. This raised hope that it would be possible to prevent two of the most common diseases among women after menopause: osteoporosis (bone loss) and cardiovascular diseases. However, in the 1990s, the first large study showed that women using HRT had an increased risk of breast cancer.<\/p>\n

Another aspect the cohort aimed to clarify was whether the very common combination of estrogen and progestin in Denmark had the same preventive effect as estrogen alone, and whether this HRT regimen increases the risk of breast cancer in the same way as estrogen alone.<\/p>\n

Inspiration from the USA<\/strong><\/p>\n

The inspiration to use nurses came from the American health study, The Nurses’ Health Study. This cohort was established in 1976 to investigate the long-term effects of oral contraceptive use.<\/p>\n

Choice of Nurses<\/strong><\/p>\n

Nurses were selected because, with their professional background, they were expected to provide reliable health information about themselves. Additionally, it was a large group of women that could easily be identified through the Danish Nurses’ Association membership registry. Finally, nurses were chosen because, in a pre-study, they had shown great interest in participating in the planned prospective epidemiological study. It has since been shown that the choice of nurses was a wise one.<\/p>\n

The Original Cohort<\/strong><\/p>\n

The original cohort includes all Danish female nurses over the age of 44 who were residing in Denmark in 1993 and were active or inactive members of the Danish Nurses’ Association. Of the 23,170 nurses who were sent a questionnaire, 19,898 responded, corresponding to a response rate of 86%.<\/p>\n

First Follow-Up Study<\/strong><\/p>\n

In 1999, a new questionnaire survey was conducted among the original cohort and among nurses who had turned 44 since 1993. A total of 31,642 questionnaires were sent out, with 24,155 responses, corresponding to a 76% response rate. Of these, 15,322 had participated in both the 1993 and 1999 surveys.<\/p>\n

Second Follow-Up Study<\/strong><\/p>\n

In 2009, the second follow-up study was conducted. Questionnaires were sent to all women who had participated in the previous surveys in 1993 and 1999. A total of 12,955 women were sent questionnaires, and 11,114 (86%) responded.<\/p>\n

Third Follow-Up Study<\/strong><\/p>\n

In December 2020, questionnaires were sent to all members of the Danish Nurses’ Association to investigate the effects of COVID-19 infection, lifestyle, work environment, fertility, sleep, and more. For the first time, male nurses were included. In total, 80,134 members received questionnaires, including 3,000 men. The response rate for the third follow-up study was 46%, which is lower than in the previous studies. This is because electronic questionnaires were sent via E-Boks for the first time. In total, 35,504 women and 1,253 men responded. This means that the Danish Nurse Cohort now includes data from 61,438 nurses.<\/p>\n

The first results of the study have been published in Sygeplejersken<\/em> (The Nurse Journal), and larger studies are currently ongoing and will be published in peer-reviewed journals.<\/p>\n

Development of the Questionnaire<\/strong><\/p>\n

Recognizing that lifestyle plays a significant role in the development of both osteoporosis, cardiovascular diseases, and cancer, the questionnaire includes a range of questions to assess nurses’ health habits, including diet, exercise, smoking habits, alcohol consumption, and self-reported health. Many of these questions were used in the Health and Sickness Surveys conducted periodically by the Danish Institute of Public Health. Additionally, the questionnaire includes questions about health conditions, reproductive health, weight management, dieting, healthcare usage, and medication use, particularly the use of oral contraceptives and HRT.<\/p>\n

The People Behind the Cohort<\/strong><\/p>\n

The cohort was initiated by Chief Physician, Dr. Med. Erik Obel, who in 1989 began collaborating with Kirsten Stallknecht, Chairwoman of the Danish Nurses’ Association, and Eva Holm Christensen, Director, to obtain permission to use the membership register of the Danish Nurses’ Association.<\/p>\n

Nurse, Ph.D. Yrsa Andersen Hundrup was the daily leader of the cohort from 1990 to 2012, after which the cohort was taken over by Mette Kildev\u00e6ld Simonsen, Senior Researcher at the Neurology Department, Frederiksberg and Bispebjerg Hospital.<\/p>\n

Scientific Data<\/strong><\/p>\n

The Danish Nurse Cohort has shown that hormone use during menopause does not protect against cardiovascular diseases and stroke, and that the most commonly used hormone regimens increase the risk of breast cancer. It has also been found that hormone use protects against typical osteoporotic fractures, but the protective effect disappears when the treatment is stopped. The cohort\u2019s data have been groundbreaking in many other areas and have had international scientific impact.<\/p>\n

The Danish Nurse Cohort is distinguished by:<\/strong><\/p>\n