A critical review of the prevalence of secondary amenorrhea in ballet dancers.
The literature was evaluated in an effort to explain the apparently high prevalence and wide range of secondary amenorrhea reported for ballet dancers. In the general population the prevalence of secondary amenorrhea is between 2% to 5%. In the ballet community the prevalence of amenorrhea is 6% to 73%. Seven of the 22 articles assessed present a prevalence of secondary amenorrhea greater than 30% for ballet dancers. Due to lack of reported information within these studies, a better understanding of the data cannot be gained. Existing reports were found deficient in the following areas: activity level, caloric intake, menstrual log, specific subject information (rank, expertise, and individual and group data), standard definition of secondary amenorrhea, methods of data collection, lack of prospective studies, and recordings of hormonal contraceptives. To enable an evaluation and explanation of the prevalence of secondary amenorrhea in ballet dancers, new research should be undertaken to include all these variables in order to provide a more complete understanding.
In the last three decades, investigation of the reproductive health of dancers has become an important area of research. Published studies shown in Table 1 report a prevalence of secondary amenorrhea among ballet dancers ranging from 6% to 73%. Secondary amenorrhea within the general population is between 2% to 5%. (1) The high prevalence of secondary amenorrhea among ballet dancers and its vast range are cause for concern. Otis and colleagues (2) listed disordered eating, amenorrhea, and osteoporosis as three related concerns for active females that they describe as the Female Athlete Triad (Triad). The Triad is of particular concern to females such as dancers that are in activities that emphasize body image and low body weight. "Internal and external pressures placed on girls and women to achieve or maintain unrealistically low body weight underlies the development of these disorders." (2) In the Triad, Otis and colleagues (2) stated that disordered eating can result in secondary hypothalamic amenorrhea, which in turn is associated with osteoporosis.
Understanding the high prevalence of secondary amenorrhea reported in the literature on ballet dancers is an important concern because of the relationship of secondary amenorrhea to the other factors of the Triad. This article critically reviews the current literature on secondary amenorrhea among ballet dancers in an effort to evaluate the accuracy of the high prevalence and broad range of secondary amenorrhea reported for ballet dancers.
The menstrual cycle is a natural process that permits the reproduction of our species. All women become intimately acquainted with menstrual cycles in their childbearing years between the second and sixth decades of life. (3) Menarche is the onset of the first menstrual cycle. The normal length of a woman's cycle has been reported to last from 25 to 45 days. (4-11) A normal menstrual cycle is referred to as eumenorrhea. When the menstrual cycle is consistently irregular, lasting between 45 to 90 days, it is referred to as oligomenorrhea. (6,8,12) Based on the most common definition used in the literature, the cessation of the menstrual cycle for 3 to 6 months or more is termed secondary amenorrhea. There are two types of amenorrhea. Primary amenorrhea is defined as delayed menarche and secondary amenorrhea occurs after menarche.
The menstrual cycle is divided into two phases, follicular and luteal, and two events, menstruation and ovulation. Changes between phases and events of the menstrual cycle are controlled by hormones from the hypothalamus, the pituitary, and the ovary. (13) Figure 1 presents a detailed schematic outlining the hormone- feedback system that controls the menstrual cycle.
[FIGURE 1 OMITTED]
Otis and colleagues (2) suggested that decreased energy availability resulting from a negative energy balance, can, in turn, result in hypothalamic changes leading to secondary amenorrhea. Chronic underfeeding among ballet dancers is well established in the literature, but not fully analyzed in light of its possible contribution to secondary amenorrhea.
Table 1 summarizes the 22 published reports that deal with or include the prevalence of secondary amenorrhea in ballet dancers. For the purpose of this review an evaluation of these studies will proceed through analysis of: energy balance, subjects, definition of secondary amenorrhea, and the evaluation procedures used. This analysis was used in an attempt to evaluate the accuracy of the high prevalence and broad range of secondary amenorrhea reported for ballet dancers.
Only three of the 22 articles in Table 1 gathered information on both energy intake and expenditure. (14-16) Four articles in Table 1 provided enough information to find the energy expenditure by recording the hours of activity per week and daily caloric intake. (7,17-19) Ten studies provided either the hours of activity or caloric intake, (6,8,9,20-26) and five of the reports did not mention either energy intake or expenditure. (12,27-30) As mentioned, energy availability is seen as a possible factor in the development of secondary amenorrhea in ballet dancers. However, it is hard to truly gauge its impact through the assessment of published reports as most did not collect data on both energy intake and expenditure.
Otis and colleagues (2) defined energy availability as dietary energy intake minus exercise energy expenditure. Energy availability is an indication of the energy remaining after daily activity has been fueled for all energy requirements. Below, using the most conservative bench marks and giving ballet dancers every possible benefit to interpret caloric intake data in their favor, it will be demonstrated that they are chronically energy deficient.
The "recommended daily allowance" (RDA) "are recommendations for average daily amounts of nutrients for population groups and should not be confused with requirements for specific individuals." (19) It is common to assess the adequacy of an individual's intake at 70% of the RDA.
The actual caloric expenditure of a typical ballet class was measured and found to be 200 kcals per hour for women. (31) Druss and Silverman (32) studied dancers at the Joffrey School of Ballet in New York City and found that the females danced for six hours of class and rehearsal per day. Based on these reports, it can be estimated that dance requires 1,200 kcals per day of energy.
Clarkson (33) performed a brief review of research on the energy intake patterns of female ballet dancers and found total average intakes that ranged from 1,358 to 1,890 kcals per day. If we calculate energy availability on this range of average intakes using 1,200 kcals as an estimate for daily dance energy requirements, we obtain an energy availability ranging from 158 to 690 kcals per day. Seventy percent of the RDA for 11- to 18-year-old females is approximately 1,540 kcals. Based on these estimates and calculations, all average intakes for groups of ballet dancers reported by Clarkson (33) have significant energy deficiencies.
Recent research has studied energy intake and expenditure in ballet communities and found a 21% under-reporting of energy intake in dancers. (34) If the 1,358 to 1,890 kcals per day range for ballet dancers reported by Clarkson (33) is adjusted to reflect a 21% under reporting, the range is adjusted upward to 1,643 to 2,287 kcals per day. If this adjusted range is used to calculate energy availability, the adjusted energy availability ranges from 443 to 1,087 kcals per day. Even with the extra 21% added on for possible under reporting, these daily energy intakes still reflect a significant energy deficiency when compared to the 70% RDA of 1,540 kcals. If these energy availability values hold true for ballet dancers in general, they could explain the high prevalence of secondary amenorrhea. It also reaffirms the importance of collecting energy intake and expenditure data in studies of secondary amenorrhea in ballet dancers.
The studies summarized in Table 1 used various procedures for sorting subjects. Often students and professional performers were combined in the same group. (14-17,19,21) When students are studied, multiple levels of expertise and individual, broadly ranging levels of aspirations and commitment are combined in the same group. (26,29) Subjects from local, regional, and national studios and companies were combined. (14-17,21) Researchers often did not provide a clear portrayal of the subjects involved in their study. This lack of information is illustrated in the six studies in Table 1 that use both pre-professional students and professional dancers. (14-17,19,21) Four of these six studies do not report the number of professionals and students involved in the study or sort the data found for each sub-group (14-16,21) and instead provided an average prevalence of secondary amenorrhea for the combined data.
As Otis and colleagues (2) indicated, peer pressure and individual and group expectations for thinness and body image can be a risk factor for disordered eating, amenorrhea, and osteoporosis. Druss and Silverman (32) commented that ballet dancers had distorted body images and that the dancers themselves thought of this as a requirement of the profession. The dancers expressed a need to control their bodies and a desire to please instructors who could advance their careers. The intensity of pressures and expectations such as these probably vary across different training environments. For example, Abraham and colleagues (6) followed a specific group of dancers in the first year of preprofessional ballet training. This group represented a homogenous sample of elite, pre-professional ballet students and reported a 69% prevalence of secondary amenorrhea. Contrast that study with Buchanan and colleagues (20) who found only a 6% prevalence of secondary amenorrhea among student ballet dancers. While the dancers in the study by Abraham and colleagues (6) were described as elite pre-professionals and worked 25 to 30 hours per week, the dancers in Buchanan and colleagues (20) were characterized as coming from community ballet schools and averaged only 6 hours or more per week of dancing. It is possible that the higher demands of the training and expectations placed upon the subjects in Abraham and colleagues (6) were responsible for the increased prevalence of secondary amenorrhea for that group compared to the subjects studied by Buchanan and colleagues. (20)
Most of the studies in Table 1 do not enable this kind of comparison. Subjects are not always sorted by level of expertise, type of school, or company expectations. A related issue arises in this regard for studies that use samples from groups instead of obtaining responses from every individual in the group. In this kind of sampling it is important to know how representative the sample is of the entire group. As the magnitude of difference between the respondents (the sample) and the non-respondents increases the sample prevalence separates further and further from the real prevalence. How much drift in a sample estimate is acceptable? There could be a systematic avoidance of responding that skews the prevalence among the non-respondents. In such a case, the sample estimate will be a poor representation of the full group. The remedy is high response rates, some recommend as high as 80%. Sampling error is reduced as the number respondents approaches the size of the full group.
Well-documented and representative sampling procedures should be used in future research and carefully described in future reports in order to understand the relevance of data collected. In addition, a more comprehensive collection and report of subject data would enable analysis of the relationship of subject categories and the prevalence of secondary amenorrhea. Based on the issues that have surfaced in this review, it seems reasonable to suggest that a comprehensive collection of relevant subject data would include the following two areas of concern:
1. The level of expertise of the subjects (e.g., beginning, intermediate, advanced, professional), and
2. The level of expectation placed on subjects both by themselves and by their environment (e.g., competition for limited spots on a professional touring company versus recreational involvement).
Definitions of Secondary Amenorrhea Used in the Literature
Menstrual cycles can fluctuate greatly among women. Authorities state that the average menstrual cycle can last anywhere from 25 to 45 days. (4-9) Oligomenorrhea is diagnosed when a woman has a menstrual cycle between 45 and 90 days. (6,8,12)
Secondary amenorrhea is defined as the absence of menstruation over time after menarche. A variance across studies in Table 1 exists in the time criterion used to define secondary amenorrhea. This time criterion ranges from 3 to 6 months without a menstrual period. Two studies in Table 1 do not even give the time criterion that was used. (26,29) This noticeable time discrepancy among definitions of secondary amenorrhea may contribute to the broad range of prevalence reported for secondary amenorrhea in ballet dancers. (17) In Williams's (10) assessment of the prevalence of secondary amenorrhea in female athletes she notes that secondary amenorrhea was found between 1% to 44% of the time. She concluded that this range was dependant on the definition of secondary amenorrhea used in the study.
The most popular criteria for the diagnosis of secondary amenorrhea found among studies in Table 1 was three months. Twelve of the 22 studies listed in Table 1 used the three months (or 90 day) criterion. If data collection occurred a day or two before 90 days or if an oligomenorrheic subject had her menstrual period a day or two after 90 days, it is possible that dancers with oligomenorrhea could have been included in the prevalence data for secondary amenorrhea. In a clinical environment 3 months monitoring for secondary amenorrhea seems a good fit for intervention. However in the research setting the 6-month criterion would be more robust for sorting subjects with secondary amenorrhea from those with oligomenorrhea.
Evaluation procedures include: methods of data collection, design, and hormonal contraceptives (HC). All elements will be examined to help better understand the evaluation procedures and the range of prevalence of secondary amenorrhea found in studies of ballet dancers and reproductive health.
Methods of Data Collection
The 22 articles collected their menstrual data by self-report and by interview. Both methods may introduce false positives and false negatives into the data. Some ballet dancers believe that the loss of the menstrual cycle is desirable, as it is seen to reflect dedication and hard work. (32) This positive perception of secondary amenorrhea might lead to its over-reporting by dancers hoping to benefit from having this reproductive dysfunction. On the other hand, other ballet dancers might not want to admit that they have secondary amenorrhea if they believe it could harm their ballet career. A dancer might under-report secondary amenorrhea if she thought she could lose her job. It also might be over or under reported if the dancer did not understand the definition being used for secondary amenorrhea and how to apply it to her situation.
It is important to consider who collects menstrual data, whether subject confidentiality will remain intact, and if the data will be shared with the administration of the school or company. In the 22 reports, only 8 give an indication of who collected the data. Sometimes data were self-reported. Other times menstrual data were recorded by either the nutritionist who verified caloric logs or the nurse practitioner who recorded medical information. (8,12,14-16,18,20,27) Ten studies explicitly stated that the researchers obtained the dancers' consent (7,15-17,21-25,28) and 9 reported that they obtained consent from a Review board or ethics committee to proceed with the study. (14-17,20-22,24,25) Only one of the 22 reports in Table 1 elucidated specifically who was allowed access to the study data. (17)
Of course, if anonymity in the data collection process is guaranteed, it does not matter who might eventually see a subject's data. However, only two studies state that they guaranteed anonymity. (17,27) Kurtzman and colleagues, (27) who found an 18% prevalence of secondary amenorrhea in their subjects, chose to collect their data by an anonymous, self-reported questionnaire. They admit that this method of data collection may limit the accuracy of the data compared to a detailed clinical interview, yet believed it may have allowed their subjects to be more honest with their answers.
Care toward data collection is important to ensure the most accurate and truthful recording of the dancer's reproductive health. It is important to guarantee confidentiality. Due to the lack of information on the methods of data collection and the assurance of confidentiality in most of the reports in the literature, it cannot be known what effect inaccurate data acquisition or lack of confidentiality may have had on the reported prevalence of secondary amenorrhea. All future studies should carefully document how data are acquired and guarantee subject confidentiality through internal Review Board Approvals and informed consent.
The retrospective study is the most popular method reported for recording menstrual information. This may be due to the minimal work needed to collect this type of data. Nineteen studies in Table 1 use a retrospective design. A retrospective study is used to recall the subject's menstrual history. It relies on the subject's understanding and memory of past cycles. This type of study requires a subject to record past experiences, such as when their last menstrual cycle was and how many times they have menstruated in a year. (18) Past menstrual patterns can help researchers determine and understand the menstrual history and present menstrual status of their subjects. The obvious weakness of a retrospective study is that subjects might not remember their past cycle fluctuations with accuracy. Hence, the information in a retrospective study must be treated with caution. It is possible that inaccurate memories could contribute to falsely high prevalence, especially in studies that use the three-month criterion for definition of secondary amenorrhea.
The prospective study collects data on an ongoing basis. It enables the researchers to track the subject's menstrual cycle and fluctuations during the study. It is important to get the most accurate portrayal of the subject's menstrual information to enable researchers to detect secondary amenorrhea. By only reporting past menstrual data, as a retrospective study would, we get a limited understanding of the dancer's menstrual patterns. Only three studies in Table 1 use a prospective design and they report a wide range of prevalence of secondary amenorrhea (10% to 73%). (6,26,30) Even though the prospective approach in these studies does not help explain the wide range of results obtained, prospective designs are recommended for future work in this area as they stand to yield the most accurate data.
Hormonal contraceptives (HC) are pharmaceutical agents administered to prevent pregnancy or regulate an irregular menstrual cycle. Women on HC will have normal menstrual cycles that are regulated by the HC. Six of the 22 studies in Table 1 did not include HC information for their subjects. (6,18,20,23,24,29) Dancers on HC would not be reported as amenorrheic so if they skewed group data it would be toward a lower prevalence. In the six studies that did not control for HC, prevalence of secondary amenorrhea ranged from 6% to 69%. (6,18,20,23,24,29) Since use of HC was not accounted for, it is impossible to assess the accuracy of these reports. Future work in this area should eliminate subjects who use HC.
In this critical review, the literature was evaluated in an effort to explain the apparently high prevalence and wide range of secondary amenorrhea reported for ballet dancers. Most articles surveyed lacked pertinent information needed to completely analyze their results. In addition, many studies did not provide data on essential areas of concern to the complete understanding of secondary amenorrhea.
These essential factors include:
* Daily energy expenditures;
* Daily caloric intake;
* Prospective menstrual log;
* Adequate descriptions of data collection, handling, and reporting procedures;
* Guarantee of subject confidentiality;
* Comprehensive subject profiling (including analysis of pressures and expectations placed on dancers);
* Detailed description of subject grouping procedures;
* Evidence of representativeness of sampling procedures when only part of a group is analyzed in a large group setting;
* Standard definition of secondary amenorrhea;
* Information on who handles data collection; and
* Elimination of subjects using hormonal contraceptives.
Without adequate information collected and reported in these areas, this review cannot assess the accuracy of the apparently high prevalence and broad range of secondary amenorrhea reported among ballet dancers. Additionally, only 6 of the 22 articles surveyed focused on the menstrual cycle or secondary amenorrhea in ballet dancers. (6,9,16,17,20,30) In the other 16 articles, secondary amenorrhea was not the main focus of research. It is recommended that future research aimed at studying the incidence of secondary amenorrhea be designed.
While most researchers agree that there are commonly held assumptions about why ballet dancers would have a high prevalence of secondary amenorrhea, no studies have carefully studied these assumptions. The first common assumption in the literature is that a high and or continuous activity level with a low caloric intake can lead to secondary amenorrhea in ballet dancers (7,15,16,21,28); however, this assumption has not been carefully evaluated.
A second common assumption is that pressures and expectations within the individual and the environment predispose ballet dancers to secondary amenorrhea. (23,32,35,36) A dancer that is climbing the ranks of a pre-professional school or company may have a higher chance of developing secondary amenorrhea due to a higher strain from personal, peer, family, school, and company expectations. This assumption leads to the recommendation that subjects be comprehensively profiled by including an analysis of the pressures and expectations placed on them.
A final assumption that is emerging in the literature is that the debilitating effects of a negative energy balance become more prevalent in some individuals. Hamilton and colleagues (37) established a link between selection processes and ballet dancer pathologies. Less selected ballet dancers reported significantly more eating problems, anorectic behaviors, and familial obesity than highly selected ballet dancers. These researchers concluded that "Dancers who have survived a stringent process of early selection may be more naturally suited to the thin body image demanded by ballet and so less at risk for development of eating problems." (37) It seems reasonable to suggest that ballet dancers that do not have a genetic predisposition to a thin body can control their body shape by suffering a negative energy balance, (18) but that by doing so they may predispose themselves to secondary amenorrhea and the other components of the Triad (disordered eating and osteoporosis).
Convincing, though indirect, evidence of hereditary differences can be seen in three of the studies in Table 1. (14-16) In each of these three studies, a three-day log recorded energy intake and expenditure three times in these two-year studies. In all three of these studies, eumenorrheic dancers had greater negative energy balances than the amenorrheics. In other words, the eumenorrheic dancers in these studies had reduced energy availability when compared to the amenorrheics and yet were somehow able to maintain normal menstrual function. Assuming that these eumenorrheic dancers were not using HC, it is reasonable to suggest that they were genetically predisposed to thinness and decreased energy requirements.
An ideal study of secondary amenorrhea in ballet dancers would follow a group of dancers during a minimum of 6 months during a dance season. If the study started in September, it would go until the end of the winter season (February or March). The researchers would carefully group subjects as recreational, company, university, professional certificate program, or pre-professional school ballet dancers. Subjects chosen would be profiled to such an extent that each dancer's level became a sorting variable. The study would define the following terms in clear language: menstrual cycle, eumenorrhea, and secondary amenorrhea. Six months or more would be used by researchers to define secondary amenorrhea. Confidentiality would be guaranteed. Prospective data for each area of concern listed above would be collected on each subject. Following these methodological procedures would enable accurate profiling of the prevalence of secondary amenorrhea among various categories of ballet dancers and help illuminate risk factors for the development of secondary amenorrhea with clarity.
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Table 1 Analytical Data for the Verification of Amenorrheic Prevalence Ranked by Prevalence of Secondary Amenorrhea Mean Subject Age Activity Study Type (Years) N Level Buchanan et al 1992 student 15 34 6+ hrs/wk Armann et al 1990 professional 21 11 49 hrs/wk Myburgh et al 1999 student and 19 21 NG professional Fogelholm et al 1996 student and 23 113 29 hrs/wk professional Hamilton et al 1986 professional 25 40 40 hrs/wk Jonnavithula student and 21 17 2,565 kcal/day et al 1993 professional To et al 1995 student 21 98 29 hrs/wk To et al 1997 student 21 64 NG To et al 2000 student 19 50 36 hrs/wk Kurtzman et al 1989 student 21 50 NG Brooks-Gunn professional 25 55 NG et al 1987 Kaufman et al 2002 professional 23 21 20+ hrs/wk Garner et al 1980 student 19 183 NG Cohen et al 1985 professional 25 12 NG Cohen et al 1982 professional 25 32 NG Calabrese et al 1983 student and 22 34 30+ hrs/wk professional 40 hrs/wk Jenkins et al 1993 professional 27 41 1+ hrs/day and olympic athletes Frusztajer et professional 21 30 NG al 1990 Warren et al 2003 student and 22 26 2,668 kcal/day professional Abraham et al 1982 student 17 29 25-30 hrs/wk Warren et al 2002 student and 22 31 2807 kcals/day professional Warren 1980 student 14 15 20 hrs/wk Caloric Intake Definition (Mean of kcal/ Amenorrhea Study Day) (months) Buchanan et al 1992 NG 3+ Armann et al 1990 1,694 3+ Myburgh et al 1999 1,568 3+ Fogelholm et al 1996 1,544 3+ Hamilton et al 1986 1,894 (N=19) 5+ Jonnavithula 1,827 5+ et al 1993 To et al 1995 NG 3+ To et al 1997 NG 3+ To et al 2000 NG 3+ Kurtzman et al 1989 NG 3+ Brooks-Gunn NG 5+ et al 1987 Kaufman et al 2002 NG 3+ Garner et al 1980 N/G N/G Cohen et al 1985 1,673 4+ Cohen et al 1982 NG 3+ Calabrese et al 1983 1,358 3+ Jenkins et al 1993 NG 6+ Frusztajer et 1,621 5+ al 1990 Warren et al 2003 1,753 5+ Abraham et al 1982 NG 3+ Warren et al 2002 1,693 5+ Warren 1980 NG NG Evaluation Percent Study Procedure Prevalence Buchanan et al 1992 self-report 6 Armann et al 1990 self-report, interview 9 Myburgh et al 1999 self-report 10 Fogelholm et al 1996 interview 10 Hamilton et al 1986 self-report 11 Jonnavithula self-report, interview 12 et al 1993 To et al 1995 self-report 13 To et al 1997 self-report, interview 16 To et al 2000 self-report 16 Kurtzman et al 1989 self-report is Brooks-Gunn self-report 19 et al 1987 Kaufman et al 2002 self-report 24 Garner et al 1980 self-report 28 Cohen et al 1985 N/G 33 Cohen et al 1982 self-report, interview 37 Calabrese et al 1983 interview 44 Jenkins et al 1993 self-report 44 Frusztajer et self-report, interview 50 al 1990 Warren et al 2003 self-report, interview 62 Abraham et al 1982 interview 69 Warren et al 2002 self-report, interview 70 Warren 1980 interview 73 NG = not given
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|Author:||Chartrand, Dominique; Chatfield, Steven J.|
|Publication:||Journal of Dance Medicine & Science|
|Date:||Jul 1, 2005|
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