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ORIGINAL RESEARCH

Knowledge and Clinical Practice Regarding Calcium Nutrition Among Obstetrician-Gynecologists

POWER, MICHAEL L. PhD; HOLZMAN, GERALD B. MD; SCHULKIN, JAY PhD

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The aging of the general population and the increasing delivery of health care through outpatient services is affecting the profession of obstetrics and gynecology. The continuing increase in the number of elderly female patients presents both a challenge and an opportunity for obstetrician-gynecologists as they increasingly become providers of primary health care for women over the life cycle.1 Nutritional counseling of patients by primary care providers is considered a critical element in the prevention of many diseases.2,3 It is unclear from the literature the extent to which obstetrician-gynecologists consider issues about nutrition important in their practice. Because calcium is generally recognized as an important nutrient for women's health, we conducted a survey on calcium nutrition and metabolism to determine the interest, practice, and educational needs of obstetrician-gynecologists with regard to nutritional questions in an ambulatory setting.

Materials and Methods

Questionnaires were mailed to 244 ACOG Fellows who comprise the Collaborative Ambulatory Research Network and to 756 other ACOG Fellows selected at random. A second mailing was sent approximately 2 months after the first to encourage nonrespondents to respond. From the results of previous surveys this sample distribution was judged likely to result in the number of non-Collaborative Ambulatory Research Network respondents to be at least equal to the number of Collaborative Ambulatory Research Network respondents, and to result in a total sample size greater than 350, the minimum necessary for the planned comparisons. The members of the Collaborative Ambulatory Research Network are obstetrician-gynecologists who voluntarily participate in questionnaire studies such as the present investigation. The Collaborative Ambulatory Research Network was established to facilitate the assessment of prevailing patterns in obstetric-gynecologic clinical practice and to help ACOG develop professional education where needed.

The survey used primarily face-valid, forced-choice questions pertaining to physicians' practices regarding and knowledge of calcium nutrition and metabolism. Other questions asked respondents to rank-order items from 1 to 5. Questions were asked about physicians' practice and knowledge in which they could check all answers that apply. The questionnaire was divided into four sections: demographic information, professional interest and clinical practice, knowledge and opinions, and education.

Data were analyzed using a personal computer-based software package (SPSS 8.0; SPSS Inc., Chicago, IL). Descriptive statistics were computed for the measures used in the analyses, which are reported as mean ± standard error (SE). Two-tailed t tests were used to compare group means of age and years since completion of residency. Group differences in responses on continuous measures were assessed using analysis of covariance, with Collaborative Ambulatory Research Network status and sex as categoric variables, and age as the covariate. Multiple pair-wise comparisons were made using Tukey's honestly significant difference test. Differences in categoric measures were assessed using the χ2 test. The nonparametric Kruskal-Wallis test was used to examine differences between age and sex in ordinal variables. All analyses were tested for significance using an alpha of .05.

Results

Data from respondents who returned the questionnaire within approximately 2 months were included in the analysis. Of the 1000 questionnaires mailed out, 189 (77.5%) of 244 Collaborative Ambulatory Research Network surveys were returned, and 232 (30.7%) of 756 non-Collaborative Ambulatory Research Network surveys were returned, for an overall response rate of 42.1%. The overall response rate and that for the Collaborative Ambulatory Research Network respondents were similar to those of previous surveys (39–48% and 60–82%, respectively). The non-Collaborative Ambulatory Research Network response rate was lower than in previous surveys (36–43%). There were no demographic differences between respondents and nonrespondents among the members of the Collaborative Ambulatory Research Network. We lacked the necessary demographic information on non-Collaborative Ambulatory Research Network Fellows to compare respondents to nonrespondents.

Data were analyzed for group differences on questionnaire item responses, using two-way analysis of covariance with sex and Collaborative Ambulatory Research Network status as between-subject factors and age as the covariate. Age and sex were significant factors for many of the questions in this survey. Membership in the Collaborative Ambulatory Research Network was not a significant factor.

Fifty-nine percent of the respondents were men and 41% were women. Respondents' average age was 43.7 ± 0.5 years, and they reported completing their specialty training an average of 13.0 ± 0.5 years ago. Collaborative Ambulatory Research Network responders were significantly older (45.3 ± 0.7 years compared with 42.3 ± 0.7 years, t = 3.11, df = 416, P < .005) and had more years of professional practice (defined as years since residency was completed) than the non-Collaborative Ambulatory Research Network responders (15 ± 0.7 years compared with 11 ± 0.7 years, t = −3.62, df = 410, P < .001). The female responders were on average younger (39.4 ± 0.5 years compared with 46.6 ± 0.7 years, t = 7.537, df = 414, P < .001) and had fewer years of professional experience than the male responders (9 ± 0.5 years compared with 16 ± 0.7 years, t = −7.656, df = 406, P < .001). The demographic change is readily apparent when the data are considered by age group. For respondents 45 years or older, 80.8% were men, whereas only 46.4% of respondents under age 45 years were men. This is consistent with the trend in residency programs over the last decade, with almost two of three current residents in obstetrics and gynecology being women.1

Most respondents indicated that they had a private practice, 60.1% of whom belonged to a group practice and 18.5% of whom were in solo practice. Relatively few respondents were in health maintenance organizations (4.0%). The respondents in solo private practice were the oldest on average (48.8 ±1.2 years). Analysis of covariance found that age was a significant factor in predicting category of practice (F = 26.4, P < .001), but sex and Collaborative Ambulatory Research Network status were not. Thus, the result that men were more likely than women to be in solo practice, and women were more likely than men to be in a multispecialty group or a university, probably reflects the changing demographics and practice patterns of obstetrician-gynecologists.

The respondents were asked to rate, on a scale from 1 (high) to 5 (none at all), their interest in nutrition and the importance of making dietary recommendations in their practice. Most respondents answered 1 or 2 to those two questions (70.0% and 75.4%, respectively). Most respondents (83%) indicated that they had some patient education materials that contained information on dietary calcium.

There was a statistically significant association between whether obstetrician-gynecologists self-reported an interest in nutrition and whether they indicated that making dietary recommendations is an important part of their practice (Pearson χ2 = 308, df = 12, P < .001). Of those who answered 1 or 2 to the question concerning interest in nutrition, 90.8% also answered 1 or 2 to the question concerning the importance of dietary recommendations in their practice. Only 43.7% of those who answered 3 or higher to having an interest in nutrition rated the importance of dietary recommendations in their practice a 1 or 2. Respondents who indicated that making dietary recommendations was an important part of their practice were more likely (48.7% compared with 31.2%) to refer patients for nutritional counseling (Pearson χ2 = 49.7, df = 16, P < .001). Although over 90% of responding obstetrician-gynecologists make dietary recommendations to their pregnant patients, only 58% do so for their nonpregnant patients. There was a significant association between considering nutrition important and making dietary recommendations to nonpregnant patients (Pearson χ2 = 114.7, df = 8, P < .001), with 67.5% of physicians who rated the importance of dietary recommendations a 1 or 2 making recommendations as opposed to only 20.2% of physicians who rated dietary recommendations as 3 or higher.

Women physicians consider dietary recommendations to be a more important part of their practice than do male physicians (Pearson χ2 = 13.4, df = 4, P = .009). On the 1 to 5 scale, women were more likely than men to select 2 (50.3% compared with 38.4%), whereas men were more likely than women to select 3 (20.0% compared with 10.1%). Women were more likely to make dietary recommendations to a wider range of patients. Specifically, they were statistically more likely to make dietary recommendations to perimenopausal, teenage, and vegetarian women than were men. There was a significant relationship between age and interest in nutrition in both men and women, with the older respondents reporting a greater interest in nutrition and being more likely to consider nutrition an important part of their practice (F = 4.94, P < .05).

The respondents were asked to select three sources of dietary calcium from a list of 20 that they would recommend to their patients. Table 1 shows the ten most frequently chosen foods by all respondents, and by male and female respondents. Although nine of ten foods were common to both the men's and women's lists, there were significant differences between men and women in the frequency with which six of those nine foods were selected. Ice cream appeared in the men's top ten list but not in the women's list, and kale was in the women's but not in the men's list. Women were more likely to select nonfat milk, yogurt, and calcium-fortified juice than were men. Men were more likely to select antacids, mineral supplements, whole milk, and ice cream than were women (Table 1).

Table 1
Table 1:
The Ten Most Commonly Selected Sources of Dietary Calcium That Respondents Would Recommend to Their Patients

Given a choice of less than 500 mg/day, about 900 mg/day, about 1200 mg/day, about 1600 mg/day, and don't know, concerning the average intake of calcium by women 11 to 24 years of age, most respondents (77.0%) selected either less than 500 mg/day (45.2%) or 900 mg/day (31.8%). Almost one in five respondents (17.9%) answered this question “don't know,” with men being more likely than women to answer “don't know” (Pearson χ2 = 15.5, df = 4, P < 0.01). Excluding the “don't know” responses, there was no difference between men and women in their responses. Respondents who reported that making dietary recommendations was an important part of their practice were more likely to answer this question < 500 mg/day, and less likely to answer “don't know” (Pearson χ2 = 55.6, df = 16, P < .001). National dietary assessment surveys using the 24-hour recall method have found that median calcium intakes by women of this age range from 600–850 mg/day.4,5

The respondents were asked to provide their recommended daily calcium intake for a variety of patients. The mean recommended calcium intakes were reasonably consistent with current guidelines for suggested daily calcium intake6 but varied widely among the individual responders (Table 2). Members of Collaborative Ambulatory Research Network recommended higher levels of calcium for nonpregnant, premenopausal women, and postmenopausal women on hormone replacement therapy (HRT) than did non-Collaborative Ambulatory Research Network respondents (t = 2.03, df = 393, P < .05). Although there was no effect of sex on the mean values for recommended intakes, men (13.6%) were more likely than women (4.3%) to have no opinion on daily calcium intake for premenopausal nonpregnant women (Pearson χ2 = 9.48, df = 1, P < .005).

Table 2
Table 2:
Respondents' Recommended Daily Calcium Intakes

More than three of four respondents rated calcium and vitamin D supplementation and HRT as an effective treatment for preventing bone loss, consistent with the scientific literature.7,8 However, there was inconsistent knowledge about some of the specific changes in physiology and behavior associated with aging that contribute to low bone mass, and knowledge varied with age and sex. Men (12.6%) were more likely than women (3.6%) to answer “don't know” to these questions (Pearson χ2 = 9.84, df = 1, P < .005). Older respondents generally were more knowledgeable. Specifically, older respondents were more aware that food intake is decreased in the elderly (Pearson χ2 = 17.6, df = 1, P < .001) and that the elderly often have low exposure to sunlight (Pearson χ2 = 8.8, df = 1, P = .003). Collaborative Ambulatory Research Network respondents were more aware that the elderly often have low sunlight exposure than were non-Collaborative Ambulatory Research Network respondents (Pearson χ2 = 6.0, df = 1, P < .05), but otherwise there were no differences between these groups.

Only 10% of respondents believed that increased calcium intake during pregnancy can reduce the incidence of preeclampsia; 35.5% answered no, 47.5% said the evidence is inconclusive, and 7% did not know. This is an area of continued controversy,9 and the responses reflect the low level of scientific certainty concerning this issue. These opinions did not vary significantly across sex or any other categoric variable surveyed.

Most respondents lacked basic knowledge about calciotropic hormones and fetal and maternal calcium metabolism during pregnancy. The majority of responses to the seven questions in this area were “don't know” (range 45.5–92.1%). There was no effect of age, sex, or attitude.

A slight majority of respondents reported reading literature pertaining to patient nutrition four or more times per year, and 79.4% reported reading such literature two or more times per year. There were no differences between men and women and no effect of age. Self-reported interest in nutrition and importance of nutrition to practice were significantly associated with more frequent reading about nutrition (Pearson χ2 =84.1, df = 16, P < .001).

The preferred methods for staying abreast of advances in nutrition were ACOG Committee Opinions, journals, and ACOG Educational Bulletins. There were a few age and sex effects, with respondents 45 years or older having a greater preference for non-continuing medical education activities (χ2 = 13.647, P = .003) and men less than 45 years old having a greater preference for text books (χ2 = 10.152, P = .017). Men 45 years or older were less likely than the other groups to use the Internet or literature searches as a source of information about nutrition (χ2 = 15.88, P = .001). However, these choices were not very highly rated, with median ratings of 5 or greater on a scale from 1 to 8. Although not significant (χ2 = 7.727, P = .052) men 45 years or older and women less than 45 years old had a greater preference for ACOG postgraduate courses than did the younger men and older women.

Discussion

Attention to nutrition and dietary habits is recognized as important for maintaining good health and reducing the incidence of many diseases.2,3 Increasing the provision of nutritional counseling by physicians is one of the objectives of the Healthy People 2000 initiative from the United States Department of Health and Human Services Public Health Service.10 National dietary surveys indicate that, on average, women ingest less calcium than men and that their average calcium intake is well below the suggested adequate intake.4,5,6,7 Low calcium intake has been linked with a variety of diseases, most notably osteoporosis,7,11 but also it has been implicated in colon cancer,12 hypertension,13 and most recently premenstrual syndrome.14

The demographic results of this survey are consistent with the documented increase in women entering the profession of obstetrics and gynecology.1 Those results also indicate that there are gender and age differences in attitudes, knowledge, and practices regarding nutrition. Older age and female gender independently were associated with a greater self-reported importance of nutrition to practice.

The gender differences might result in different practice patterns. For example, when recommending dietary sources of calcium, men were more likely than women to recommend nonfood sources (antacids and mineral supplements) and to recommend higher fat foods (eg, whole milk and ice cream). Calcium has been suggested as a marker for a healthy diet, as low calcium intake is associated with low intakes of other nutrients.15 Calcium supplements are unlikely to correct other vitamin deficiencies that might be corrected by the addition of calcium-rich foods to a diet.

It is unlikely that the age differences reflect a generational difference in the perceived role of nutrition to health. A possible interpretation is that physicians gain knowledge and appreciation of nutrition over time. That implies that current medical curricula might not adequately prepare physicians to provide effective nutritional counseling to their patients. Despite a general acceptance by physicians of the role of nutrition in patient health and disease, increasing the nutrition curriculum in medical schools has proved difficult.16

Overall, the results of this survey indicate a relatively high appreciation of the importance of nutrition to health by obstetrician-gynecologists. The percentage of respondents who considered making recommendations concerning diet an important part of their practice (75.4%) was similar to that found in a survey of other primary care practitioners.17 Despite significant incomplete or inaccurate knowledge concerning the specifics of calcium metabolism and regulation, the respondents to this survey were aware of the low calcium intake among women in the United States and the importance of calcium in health and disease.

References

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© 1999 The American College of Obstetricians and Gynecologists