- Email: [email protected]
Lower bone mass detected at femoral neck and lumbar spine in lower-weight vs normal-weight small-boned women
RESEARCH AND PROFESSIONAL BRIEFS
Lower bone mass detected at femoral neck and lumbar spine in lower-weight vs normal-weight small-boned women DEE ROLLINS, PhD, RD; VICTORINE IMRHAN, PhD, RD; DORISE MARIE CZAJKA-NARINS, PhD; DAVID L. NICHOLS, PhD
ABSTRACT Sixty-one nonsmoking, healthy, young, menstruating women aged 18 to 30 years generally considered at peak skeletal bone mass were screened for diseases and drugs known to adversely affect bone mineral density (BMD). Anthropometric measures, BMD of the lumbar spine (LS) and femoral neck (FN), exercise time, selected nutrient, and energy intake were compared. The women were categorized by frame size and body mass index (BMI), with the upper range for normal weight (NW) being BMI 23.0 to 25.9 (n⫽30) and lower weight (LW) being BMI 16.0-19.9 (n⫽31). Multivariate t tests, Pearson correlations, and independent sample t tests were used for statistical analysis. Ten of 21 in the LW group, all with small frames, had varying degrees of low BMD of the LS and/or FN. The amount of exercise time was greater in the NW group. Energy and nutrient intakes did not differ significantly between groups. J Am Diet Assoc. 2003;103:742-744.
eak bone development begins in childhood and continues into early puberty with bone elongation and growth (1,2), followed by bone mineralization and maximum calcium deposition in later puberty (3,4). Some researchers indicate that peak bone mass occurs approximately 2 years postmenarche in females (5,6), whereas others have found small gains in bone mineral density (BMD) into the third decade of life (7,8). Numerous factors affect bone mineral accretion during childhood and puberty. Chronic dieting to maintain a low body weight, low calcium intake, cigarette use or alcohol abuse, and limited physical activity, both past and present, are known to decrease BMD (9-15). Some medical
P
disorders such as endocrine and gastrointestinal disorders, anorexia nervosa, and use of medications such as corticosteroids and anticonvulsants reduce bone mass (16-18). Many of these factors produce what is termed secondary osteoporosis (19,20). The objective of this study was to evaluate BMD levels of the lumbar spine and femoral neck in healthy young women who do not have lifestyle and medical conditions that might predispose them to secondary osteoporosis. The expectation was that healthy, young women, having developed peak bone mass, would have BMD levels in the normal range, providing a strong skeletal foundation as they move through life from pre- to postmenopause.
D. Rollins is a clinical dietitian and nutrition educator at Baylor Medical Center, Grapevine, TX, and adjunct professor at Tarrant County College, Arlington, TX. V. Imrhan is an associate professor, D. M. Czajka-Narins is a former professor, and D. L. Nichols is an assistant research professor at Texas Women’s University, Denton, TX. Address correspondence to: Dee Rollins, PhD, RD, LD, 1614 Heatherbrook Ct., Southlake, TX 76092. E-mail: [email protected] Copyright © 2003 by the American Dietetic Association. 0002-8223/03/10306-0010$35.00/0 doi: 10.1053/jada.2003.50138 742 / June 2003 Volume 103 Number 6
METHODS The Institutional Review Board of Texas Woman’s University, Denton, Texas, granted approval for this study. Written consent was obtained before data were collected from December 1999 to March 2000. Sixty-one women aged 18 to 30 years from college campuses and business communities were accepted for this study after being screened and interviewed to eliminate pregnancy, amenorrhea, specific medication (anticonvulsants, oral corticosteroids, and diuretics), cigarette and excessive alcohol use, and any medical diagnosis of past or current eating disorder or medically treated disease known to affect BMD. Thirty-one women with a body mass index (BMI) of 16.0 to 19.9 composed the lower-weight (LW) study group, and 30 women with a BMI of 23.0 to 25.9 composed the normal-weight (NW) group for age-matched controls. Anthropometric measurements were gathered from each participant using standard techniques. Body frame size was estimated for further intragroup evaluation by comparing wrist to height measurements to established frame size data published by Linder and Linder (21). Percentage body fat was obtained from dual-energy x-ray absorptiometry (DXA) measurements. Each participant was asked to estimate the amount of time in minutes per week that she currently participated in some type of exercise or physical activity, including walking, running, biking, swimming, aerobics, dance, calisthenics, weight training, or other type of activity. She was also asked about her involvement in physical activity or athletics during childhood and high school, including gymnastics, dance, cheerleading, and sports. All participants were given instructions for completing a self-report, 5-day food intake record at home the week prior to their scheduled bone scan. Each record was reviewed with the participant to verify accurate inclusion of type and amount of food, beverage, and supplement intake for 3 weekdays and 2 weekend days. Nutrient intakes were estimated using the Windows-based Nutrition Data System for Research (NDS-R) software version 4.01 (1998), developed by the Nutrition Coordinating Center (NCC) at the University of Minnesota. A full body DXA scan was performed on each participant using the Lunar DPX system (Lunar Radiation Corp., Madison WI), with software version Lunar 3.65, released in 1997. BMD levels for the
RESEARCH AND PROFESSIONAL BRIEFS
Table 1 Demographic and anthropometric characteristics for normal-weight and lighter-weight participants Normal weight (Nⴝ30)
Lighter weight (Nⴝ31)
4™™™™™™™™™™™™™™™™™™Mean⫾SDa™™™™™™™™™™™™™™™™™3 23.7⫾3.5 24.3⫾3.3 64.7⫾2.6 65.3⫾2.6 146.1⫾12.2 114.8⫾11.5 24.6⫾.9 18.9⫾1.0 34⫾4 24⫾5 10.5⫾4.1 10.8⫾3.5 261⫾259 148⫾154 1,869⫾487 1,830⫾407 1,002⫾370 973⫾414 246⫾58 238⫾60 71⫾18 69⫾17 68⫾28 68⫾22 17⫾6 15⫾7
Age (y) Height (in) Weight (lb)* BMI (kg/m2)* % Body fat* Gynecologic age (y)b Physical activity (min/wk)** Kcal in diet Calcium in diet (mg) Carbohydrate in diet (g) Protein in diet (g) Fat in diet (g) Fiber (g) a
SD⫽standard deviation. Gynecologic age is the number of years since the first menses. * Results significant at P⬍.01 using independent sample t test. ** Results significant at P⬍.05 using independent sample t test. b
L2-L4 lumbar spine and femoral neck with corresponding T scores based on a reference population of young, healthy women age 20 to 45 years were used.
t tests were run to determine significant differences on the variables measured. Results were deemed significant if P⬍.05.
STATISTICAL ANALYSIS Statistical analysis was performed using SPSS 10.0 for Windows (1999; SPSS Inc., Chicago, IL). Descriptive statistics were computed for all dependent variables measured. A Pearson product-moment correlation was performed to determine the existence of any statistical relationships between variables. When multivariate t tests were significant, independent
RESULTS There were no statistical differences between groups for age, height, or gynecologic age (years from menarche to current age). Body weight, BMI, and percentage body fat were significantly different between the groups (Table 1). In the NW group, body weight was significantly correlated to the femoral neck BMD (r⫽0.380; P⬍.05), and BMI was
significantly correlated to the lumbar spine BMD (r⫽0.468; P⬍.01). No such correlation existed in the LW group. Body frame size estimations indicated that more participants were considered to have a small frame size in the LW group and medium or large frame sizes in the NW group (Table 2). Only the length of time reported in current physical activity was significantly different between groups. The NW group exercised an average of 4.35 hours/week compared with 2.46 hours/ week for the LW group (Table 1). The NW group more often reported that they participated in multiple athletic, exercise, or workout events, whereas the LW group was more likely to consider brisk walking or a single exercise or workout event as their physical activity. Physical activity in the NW group showed a significant and positive correlation with the BMD of the lumbar spine (r⫽0.562; P⬍.01); however, no positive correlation was seen in the LW group. There was no significant difference between groups in the mean amount of energy, calcium, carbohydrate, protein, fat, or fiber consumed (Table 1) and no correlations to BMD levels. Results of BMD levels and T scores of the femoral neck and lumbar spine between groups were significantly different in the small-framed women but not for the medium- or large-framed women (Table 2). To investigate the nature of this difference, further analysis involved looking at individual T scores for all 61 participants. In the NW group, two me-
Table 2 Mean bone mineral density and T scores for lumbar spine and femoral neck for normal-weight and lower-weight participants by frame size within each group Normal weight (Nⴝ30) S ⴝ5, Mbⴝ14, Lcⴝ11
Lighter weight (Nⴝ31) S ⴝ21, Mbⴝ8, Lcⴝ2
a
Mean BMD lumbar spine (g/cm2) Total group Small frame Medium frame Large frame
Mean T score lumbar spine
Mean BMD femoral neck (g/cm2)
a
Mean T score femoral neck
Mean BMD lumbar spine (g/cm2)
Mean T score lumbar spine
Mean BMD femoral neck (g/cm2)
Mean T score femoral neck
4™™™™™™™™™™™™™™™™™™™™™™™™™™™™™™™™™™™™™™™™™™™™™™™™™™™™™™™Mean⫾SDd™™™™™™™™™™™™™™™™™™™™™™™™™™™™™™™™™™™™™™™™™™™™™™™™™™™™™™3 1.24⫾0.11 0.27⫾0.95 1.08⫾0.09 0.78⫾0.64 1.14⫾0.10 ⫺0.44⫾0.86 0.97⫾0.10 ⫺0.50⫾0.80 1.24⫾0.05 0.37⫾0.39 1.09⫾0.09 0.93⫾0.73 1.12⫾0.10* ⫺0.69⫾0.84 0.96⫾0.10* ⫺0.15⫾0.87 1.20⫾0.10 ⫺0.03⫾0.96 1.08⫾0.09 0.70⫾0.62 1.23⫾0.08 0.21⫾0.70 1.02⫾0.07 0.31⫾0.54 1.28⫾0.14 0.54⫾1.11 1.08⫾0.08 0.78⫾0.68 1.15⫾0.01 ⫺0.46⫾0.07 0.925⫾0.07 ⫺0.46⫾0.57
NOTE. Frame Size: Wrist circumference measured distal to the styloid process of the radius and ulna was compared with height without shoes using the chart for small, medium, or large frame size as established by Linder and Linder (21). a Small-framed women. b Medium-framed women. c Large-framed women. d SD⫽standard deviation. * Results significant at P⬍.01 using independent sample t test.
Journal of THE AMERICAN DIETETIC ASSOCIATION / 743
RESEARCH AND PROFESSIONAL BRIEFS
dium-framed women had a T score of the lumbar spine (⫺1.10 and ⫺1.28) in the osteopenia range. None of the NW group women had T scores in the osteopenia range for the femoral neck. Nine smallframed women of the LW group had T scores in the osteopenia range for the lumbar spine (range: ⫺1.02 to ⫺2.29). Three small-framed women (two with osteopenia of the spine) in the LW group had T scores in the osteopenia range for the femoral neck (range: ⫺1.01 to ⫺1.26). A T score of 0 to ⫺1 standard deviation is within normal limits. A T score of ⬎⫺1.0 but ⬍⫺2.5 is indicative of low bone mass or osteopenia, and a T score below ⫺2.5 is indicative of osteoporosis (22,23). DISCUSSION Professor Charles E. Dent of London is reported as saying that “senile osteoporosis is a pediatric disease” (2). That is that failure to reach peak bone mass during developmental years may predispose the individual to osteoporosis in old age, especially as bone mass is lost with aging. If osteoporosis has its genesis in youth and its presentation in older age, then detection with densitometry earlier in life, by the third or fourth decade, particularly in susceptible or thin, small-boned women, would allow more time for intervention (24). Current recommendations are to screen with a DXA scan at menopause (25) or 10 years after menopause (26). Results from a longitudinal observation study from the National Osteoporosis Risk Assessment (NORA) indicated that 39.6% of women 50 years or older (n⫽200,160) screened with peripheral bone densitometry using World Health Organization (WHO) BMD T score criteria had osteopenia, and 7.2% had osteoporosis (27). Nearly half of the women in the NORA population with low BMD had not previously been diagnosed. Results from this current study showed that, in a population of healthy, volunteer, premenopausal women, BMD T scores were within normal range except for about half (10 of 21) of the lower-weight, small-framed women. For the entire group of 61 participants, this was 6.1% of the study population under the age of 30 years who were categorized with osteopenia using the WHO T score criteria. Limitations of the study include nonrandom selection of volunteers who may be more prone to healthy behaviors,
744 / June 2003 Volume 103 Number 6
leading to better bone health than the general public. Also, accuracy or bias of the self-reporting tools used such as the food intake, exercise history, and eating disorder inventories may lead to under or over reporting, distortion, denial, and dishonest reporting or minimization of symptoms. Furthermore, no WHO T score definition has been established for premenopausal women; however, probably for lack of other guidelines, the T score definition for postmenopausal women is becoming universally used as a screening tool in clinical practice for all age groups (28) to detect low bone mass.
APPLICATIONS Production of peak bone mass is preferred to less effective osteoporosis treatment. ■ Dietetics practitioners can provide age appropriate nutrition education information to public school age children about the value of a routine healthful diet and the hazards to bone development of smoking, excessive drinking, sedentary lifestyle, and chronic dieting. ■ Dietetics practitioners can remind premenopausal women, particularly thinner, small-boned women, to consume adequate dairy products and/or to supplement their daily healthful diet with calcium and adequate exercise. Further bone health studies need to be conducted on this age group and guidelines established to indicate safe levels for bone mass. ■
References 1. Bass S, Delmas PD, Pearcel G, Hendrich E, Tabensky A, Seeman E. The differing tempo of growth in bone size, mass, and density in girls is region specific. J Clin Invest. 1999;104:795-804. 2. Riggs BL, Khosla S, Melton J. The assembly of the adult skeleton during growth and maturation: Implications for senile osteoporosis. J Clin Invest. 1999;104:671-672. 3. Martin AD, Bailey DA, McKay HA, Whiting S. Bone mineral and calcium accretion during puberty. Am J Clin Nutr. 1997;66:611-615. 4. Molgaard C, Thomsen BL, Michaelson, KF. Whole body bone mineral accretion in healthy children and adolescents. Arch Dis Child. 1999;81:1015. 5. Bachrach, LK. Bone mineralization in childhood and adolescence. Curr Opin Pediatr. 1993:5:467473. 6. Theintz G, Buchs B, Rizzoli R, Sloshman D, Clavien H, Sizonenki PC, Bonjour JPH. Longitudinal monitoring of bone mass accumulation in healthy adolescents: Evidence for a marked reduction after 16 years of age at the levels of lumbar spine and femoral neck in female subjects. J Clini Endocrinol Metab. 1992;75:1060-1065. 7. Recker RR, Davies M, Hinders SM, Heaney RP,
Stegman MR, Kimmell DB. Bone gain in young adult women. JAMA. 1992;268:2403-2408. 8. Teegarden D, Proulx WR, Martin BR, Zhao J, McCabe GP, Lyle RM, Peacock M, Slemenda C, Johnston CC, Weaver CM. Peak bone mass in young women. J Bone Miner Res. 1995;10:711715. 9. Hawker GA, Jamal SA, Ridout R, Chase C. A clinical prediction rule to identify premenopausal women with low bone mass. Osteoporos Int. 2002; 13:400-406. 10. Lytle LA. Nutritional issues for adolescents. J Am Diet Assoc. 2002;102(suppl 3):8S-12S. 11. Moniz C. Alcohol and bone. Br Med Bull. 1994; 50:67-75. 12. Jones G, Scott FS. A Cross-sectional study of smoking and bone mineral density in premenopausal parous women: Effect of body mass index, breastfeeding, and sports participation. J Bone Miner Res. 1999;14:1628-1633. 13. Wardlaw GM. Putting body weight and osteoporosis into perspective. Am J Clin Nutr. 1996;63: 433S-436S. 14. IIich-Ernst J, Brownbill RA, Ludemann MA, Fu R. Critical factors for bone health in women across the age span: How important is muscle mass? Medscape Women’s Health eJournal 7(3); 2002. 15. Uusi-Rasi K, Sievanen H, Pasanen M, Oja P, Vuori L. Association of physical activity and calcium intake with the maintenance of bone mass in premenopausal women. Osteoporos Int. 2002;13: 211-217. 16. Carmichael KA, Carmichael DH. Bone metabolism and osteopenia in eating disorders. Medicine. 1995;74;254-267. 17. Jones G, Sambrook PN. Drug-induced disorders of bone metabolism. Drug Saf. 1994;10:480489. 18. Adachi J, Ioannidis G. Primer On Corticosteroid-Induced Osteoporosis. Philadelphia, PA: Lippincott Williams and Wilkins; 2000:1-37. 19. Khosla S, Lufkin EG, Hodgson SF, Fitzpatrick LA, Melton LJ. Epidemiology and clinical features of osteoporosis in young individuals. Bone. 1994; 15:551-555. 20. Fitzpatrick, LA. Secondary causes of osteoporosis. Mayo Clin Proc. 2002;77:453-68. 21. Linder P, Linder D. How to Assess Degrees of Fatness. Cambridge, MD: Cambridge Scientific Industries; 1987. 22. The WHO Study Group: Assessment of Fracture Risk and Its Application to Screening for Postmenopausal Osteoporosis. Switzerland: World Health Organization; 1994. 23. Delmas PD. Do we need to change the WHO definition of osteoporosis? Osteoporos Int. 2000; 11:189-191. 24. Castelo-Branco C. Management of osteoporosis: An overview. Drugs Aging. 1998;12(suppl 1):25-32. 25. Kanis JA. The assessment of fracture risk and its application to screening for postmenopausal osteoporosis: Synopsis of a WHO report. Osteoporos Int. 1994;4:368-381. 26. Kleerekoper M. Detecting osteoporosis: Beyond the history and physical examination. Postgrad Med. 1998;103:45-68. 27. Siris ES, Miller PD, Barrett-Connor E, Faulkner KG, Wehren LE, Abbott TA, Berger MC, Santora AC, Sherwood LM. Identification and fracture outcomes of undiagnosed low bone mineral density in postmenopausal women. JAMA. 2001;286:28152822. 28. Fogelman I. Screening for osteoporosis. BMJ. 1999;319:1148-1149.
Lower bone mass detected at femoral neck and lumbar spine in lower-weight vs normal-weight small-boned women DEE ROLLINS, PhD, RD; VICTORINE IMRHAN, PhD, RD; DORISE MARIE CZAJKA-NARINS, PhD; DAVID L. NICHOLS, PhD
ABSTRACT Sixty-one nonsmoking, healthy, young, menstruating women aged 18 to 30 years generally considered at peak skeletal bone mass were screened for diseases and drugs known to adversely affect bone mineral density (BMD). Anthropometric measures, BMD of the lumbar spine (LS) and femoral neck (FN), exercise time, selected nutrient, and energy intake were compared. The women were categorized by frame size and body mass index (BMI), with the upper range for normal weight (NW) being BMI 23.0 to 25.9 (n⫽30) and lower weight (LW) being BMI 16.0-19.9 (n⫽31). Multivariate t tests, Pearson correlations, and independent sample t tests were used for statistical analysis. Ten of 21 in the LW group, all with small frames, had varying degrees of low BMD of the LS and/or FN. The amount of exercise time was greater in the NW group. Energy and nutrient intakes did not differ significantly between groups. J Am Diet Assoc. 2003;103:742-744.
eak bone development begins in childhood and continues into early puberty with bone elongation and growth (1,2), followed by bone mineralization and maximum calcium deposition in later puberty (3,4). Some researchers indicate that peak bone mass occurs approximately 2 years postmenarche in females (5,6), whereas others have found small gains in bone mineral density (BMD) into the third decade of life (7,8). Numerous factors affect bone mineral accretion during childhood and puberty. Chronic dieting to maintain a low body weight, low calcium intake, cigarette use or alcohol abuse, and limited physical activity, both past and present, are known to decrease BMD (9-15). Some medical
P
disorders such as endocrine and gastrointestinal disorders, anorexia nervosa, and use of medications such as corticosteroids and anticonvulsants reduce bone mass (16-18). Many of these factors produce what is termed secondary osteoporosis (19,20). The objective of this study was to evaluate BMD levels of the lumbar spine and femoral neck in healthy young women who do not have lifestyle and medical conditions that might predispose them to secondary osteoporosis. The expectation was that healthy, young women, having developed peak bone mass, would have BMD levels in the normal range, providing a strong skeletal foundation as they move through life from pre- to postmenopause.
D. Rollins is a clinical dietitian and nutrition educator at Baylor Medical Center, Grapevine, TX, and adjunct professor at Tarrant County College, Arlington, TX. V. Imrhan is an associate professor, D. M. Czajka-Narins is a former professor, and D. L. Nichols is an assistant research professor at Texas Women’s University, Denton, TX. Address correspondence to: Dee Rollins, PhD, RD, LD, 1614 Heatherbrook Ct., Southlake, TX 76092. E-mail: [email protected] Copyright © 2003 by the American Dietetic Association. 0002-8223/03/10306-0010$35.00/0 doi: 10.1053/jada.2003.50138 742 / June 2003 Volume 103 Number 6
METHODS The Institutional Review Board of Texas Woman’s University, Denton, Texas, granted approval for this study. Written consent was obtained before data were collected from December 1999 to March 2000. Sixty-one women aged 18 to 30 years from college campuses and business communities were accepted for this study after being screened and interviewed to eliminate pregnancy, amenorrhea, specific medication (anticonvulsants, oral corticosteroids, and diuretics), cigarette and excessive alcohol use, and any medical diagnosis of past or current eating disorder or medically treated disease known to affect BMD. Thirty-one women with a body mass index (BMI) of 16.0 to 19.9 composed the lower-weight (LW) study group, and 30 women with a BMI of 23.0 to 25.9 composed the normal-weight (NW) group for age-matched controls. Anthropometric measurements were gathered from each participant using standard techniques. Body frame size was estimated for further intragroup evaluation by comparing wrist to height measurements to established frame size data published by Linder and Linder (21). Percentage body fat was obtained from dual-energy x-ray absorptiometry (DXA) measurements. Each participant was asked to estimate the amount of time in minutes per week that she currently participated in some type of exercise or physical activity, including walking, running, biking, swimming, aerobics, dance, calisthenics, weight training, or other type of activity. She was also asked about her involvement in physical activity or athletics during childhood and high school, including gymnastics, dance, cheerleading, and sports. All participants were given instructions for completing a self-report, 5-day food intake record at home the week prior to their scheduled bone scan. Each record was reviewed with the participant to verify accurate inclusion of type and amount of food, beverage, and supplement intake for 3 weekdays and 2 weekend days. Nutrient intakes were estimated using the Windows-based Nutrition Data System for Research (NDS-R) software version 4.01 (1998), developed by the Nutrition Coordinating Center (NCC) at the University of Minnesota. A full body DXA scan was performed on each participant using the Lunar DPX system (Lunar Radiation Corp., Madison WI), with software version Lunar 3.65, released in 1997. BMD levels for the
RESEARCH AND PROFESSIONAL BRIEFS
Table 1 Demographic and anthropometric characteristics for normal-weight and lighter-weight participants Normal weight (Nⴝ30)
Lighter weight (Nⴝ31)
4™™™™™™™™™™™™™™™™™™Mean⫾SDa™™™™™™™™™™™™™™™™™3 23.7⫾3.5 24.3⫾3.3 64.7⫾2.6 65.3⫾2.6 146.1⫾12.2 114.8⫾11.5 24.6⫾.9 18.9⫾1.0 34⫾4 24⫾5 10.5⫾4.1 10.8⫾3.5 261⫾259 148⫾154 1,869⫾487 1,830⫾407 1,002⫾370 973⫾414 246⫾58 238⫾60 71⫾18 69⫾17 68⫾28 68⫾22 17⫾6 15⫾7
Age (y) Height (in) Weight (lb)* BMI (kg/m2)* % Body fat* Gynecologic age (y)b Physical activity (min/wk)** Kcal in diet Calcium in diet (mg) Carbohydrate in diet (g) Protein in diet (g) Fat in diet (g) Fiber (g) a
SD⫽standard deviation. Gynecologic age is the number of years since the first menses. * Results significant at P⬍.01 using independent sample t test. ** Results significant at P⬍.05 using independent sample t test. b
L2-L4 lumbar spine and femoral neck with corresponding T scores based on a reference population of young, healthy women age 20 to 45 years were used.
t tests were run to determine significant differences on the variables measured. Results were deemed significant if P⬍.05.
STATISTICAL ANALYSIS Statistical analysis was performed using SPSS 10.0 for Windows (1999; SPSS Inc., Chicago, IL). Descriptive statistics were computed for all dependent variables measured. A Pearson product-moment correlation was performed to determine the existence of any statistical relationships between variables. When multivariate t tests were significant, independent
RESULTS There were no statistical differences between groups for age, height, or gynecologic age (years from menarche to current age). Body weight, BMI, and percentage body fat were significantly different between the groups (Table 1). In the NW group, body weight was significantly correlated to the femoral neck BMD (r⫽0.380; P⬍.05), and BMI was
significantly correlated to the lumbar spine BMD (r⫽0.468; P⬍.01). No such correlation existed in the LW group. Body frame size estimations indicated that more participants were considered to have a small frame size in the LW group and medium or large frame sizes in the NW group (Table 2). Only the length of time reported in current physical activity was significantly different between groups. The NW group exercised an average of 4.35 hours/week compared with 2.46 hours/ week for the LW group (Table 1). The NW group more often reported that they participated in multiple athletic, exercise, or workout events, whereas the LW group was more likely to consider brisk walking or a single exercise or workout event as their physical activity. Physical activity in the NW group showed a significant and positive correlation with the BMD of the lumbar spine (r⫽0.562; P⬍.01); however, no positive correlation was seen in the LW group. There was no significant difference between groups in the mean amount of energy, calcium, carbohydrate, protein, fat, or fiber consumed (Table 1) and no correlations to BMD levels. Results of BMD levels and T scores of the femoral neck and lumbar spine between groups were significantly different in the small-framed women but not for the medium- or large-framed women (Table 2). To investigate the nature of this difference, further analysis involved looking at individual T scores for all 61 participants. In the NW group, two me-
Table 2 Mean bone mineral density and T scores for lumbar spine and femoral neck for normal-weight and lower-weight participants by frame size within each group Normal weight (Nⴝ30) S ⴝ5, Mbⴝ14, Lcⴝ11
Lighter weight (Nⴝ31) S ⴝ21, Mbⴝ8, Lcⴝ2
a
Mean BMD lumbar spine (g/cm2) Total group Small frame Medium frame Large frame
Mean T score lumbar spine
Mean BMD femoral neck (g/cm2)
a
Mean T score femoral neck
Mean BMD lumbar spine (g/cm2)
Mean T score lumbar spine
Mean BMD femoral neck (g/cm2)
Mean T score femoral neck
4™™™™™™™™™™™™™™™™™™™™™™™™™™™™™™™™™™™™™™™™™™™™™™™™™™™™™™™Mean⫾SDd™™™™™™™™™™™™™™™™™™™™™™™™™™™™™™™™™™™™™™™™™™™™™™™™™™™™™™3 1.24⫾0.11 0.27⫾0.95 1.08⫾0.09 0.78⫾0.64 1.14⫾0.10 ⫺0.44⫾0.86 0.97⫾0.10 ⫺0.50⫾0.80 1.24⫾0.05 0.37⫾0.39 1.09⫾0.09 0.93⫾0.73 1.12⫾0.10* ⫺0.69⫾0.84 0.96⫾0.10* ⫺0.15⫾0.87 1.20⫾0.10 ⫺0.03⫾0.96 1.08⫾0.09 0.70⫾0.62 1.23⫾0.08 0.21⫾0.70 1.02⫾0.07 0.31⫾0.54 1.28⫾0.14 0.54⫾1.11 1.08⫾0.08 0.78⫾0.68 1.15⫾0.01 ⫺0.46⫾0.07 0.925⫾0.07 ⫺0.46⫾0.57
NOTE. Frame Size: Wrist circumference measured distal to the styloid process of the radius and ulna was compared with height without shoes using the chart for small, medium, or large frame size as established by Linder and Linder (21). a Small-framed women. b Medium-framed women. c Large-framed women. d SD⫽standard deviation. * Results significant at P⬍.01 using independent sample t test.
Journal of THE AMERICAN DIETETIC ASSOCIATION / 743
RESEARCH AND PROFESSIONAL BRIEFS
dium-framed women had a T score of the lumbar spine (⫺1.10 and ⫺1.28) in the osteopenia range. None of the NW group women had T scores in the osteopenia range for the femoral neck. Nine smallframed women of the LW group had T scores in the osteopenia range for the lumbar spine (range: ⫺1.02 to ⫺2.29). Three small-framed women (two with osteopenia of the spine) in the LW group had T scores in the osteopenia range for the femoral neck (range: ⫺1.01 to ⫺1.26). A T score of 0 to ⫺1 standard deviation is within normal limits. A T score of ⬎⫺1.0 but ⬍⫺2.5 is indicative of low bone mass or osteopenia, and a T score below ⫺2.5 is indicative of osteoporosis (22,23). DISCUSSION Professor Charles E. Dent of London is reported as saying that “senile osteoporosis is a pediatric disease” (2). That is that failure to reach peak bone mass during developmental years may predispose the individual to osteoporosis in old age, especially as bone mass is lost with aging. If osteoporosis has its genesis in youth and its presentation in older age, then detection with densitometry earlier in life, by the third or fourth decade, particularly in susceptible or thin, small-boned women, would allow more time for intervention (24). Current recommendations are to screen with a DXA scan at menopause (25) or 10 years after menopause (26). Results from a longitudinal observation study from the National Osteoporosis Risk Assessment (NORA) indicated that 39.6% of women 50 years or older (n⫽200,160) screened with peripheral bone densitometry using World Health Organization (WHO) BMD T score criteria had osteopenia, and 7.2% had osteoporosis (27). Nearly half of the women in the NORA population with low BMD had not previously been diagnosed. Results from this current study showed that, in a population of healthy, volunteer, premenopausal women, BMD T scores were within normal range except for about half (10 of 21) of the lower-weight, small-framed women. For the entire group of 61 participants, this was 6.1% of the study population under the age of 30 years who were categorized with osteopenia using the WHO T score criteria. Limitations of the study include nonrandom selection of volunteers who may be more prone to healthy behaviors,
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leading to better bone health than the general public. Also, accuracy or bias of the self-reporting tools used such as the food intake, exercise history, and eating disorder inventories may lead to under or over reporting, distortion, denial, and dishonest reporting or minimization of symptoms. Furthermore, no WHO T score definition has been established for premenopausal women; however, probably for lack of other guidelines, the T score definition for postmenopausal women is becoming universally used as a screening tool in clinical practice for all age groups (28) to detect low bone mass.
APPLICATIONS Production of peak bone mass is preferred to less effective osteoporosis treatment. ■ Dietetics practitioners can provide age appropriate nutrition education information to public school age children about the value of a routine healthful diet and the hazards to bone development of smoking, excessive drinking, sedentary lifestyle, and chronic dieting. ■ Dietetics practitioners can remind premenopausal women, particularly thinner, small-boned women, to consume adequate dairy products and/or to supplement their daily healthful diet with calcium and adequate exercise. Further bone health studies need to be conducted on this age group and guidelines established to indicate safe levels for bone mass. ■
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