HOMO - Journal of Comparative Human Biology 65 (2014) 232–239
Contents lists available at ScienceDirect
HOMO - Journal of Comparative Human Biology journal homepage: www.elsevier.com/locate/jchb
The optimal value of BMI for the lowest risk of osteoporosis in postmenopausal women aged 40–88 years A. Skrzek a, S. Kozieł b,∗, Z. Ignasiak a a b
University School of Physical Education in Wrocław, Al. I. Paderewskiego 35, 51-612 Wrocław, Poland Polish Academy of Sciences, Unit of Anthropology in Wrocław, Podwale 75, 50-449 Wrocław, Poland
a r t i c l e
i n f o
Article history: Received 9 May 2012 Accepted 8 January 2014
a b s t r a c t The aim of this paper is to establish the optimal values of the body mass index (BMI) which would indicate the most favourable preservation of the bone mineral density in postmenopausal women. The material consists of the data of 369 healthy women aged between 40 and 88 years (mean age 67.84, SD = 6.70) inhabitants of Wrocław, which were followed up between 2001 and 2006. The absolute measure of bone mineral density (BMD) of the femoral neck was assessed using dual energy X-ray absorptiometry (DEXA), expressed in g/(100 mm2 ) and was transformed to T-score values. According to the value of BMI, the women were divided into eight groups, the reference group with value between 18.0 and 21.9 kg/m2 and seven other groups beginning with the value 22.0 with a 2-point interval. Postmenopausal status was defined according to the occurrence of menstruation within the last 360 days. The women with osteopenia and osteoporosis were pooled together and comprised the risk group, whereas the other women comprised the normal group (T-score values above −1.0). The adjusted odds ratio showed the highest value for intervals between 24.0 and 25.9 units of BMI, and the lowest value for interval 26.0–27.9 units of BMI. The Youden index showed the lowest value in the 26.0–27.9 BMI kg/m2 interval. For our sample the optimal value of BMI, with the lowest risk of osteopenia and/or osteoporosis was the value of 26.9 kg/m2 . A further increase of BMI does not
∗ Corresponding author. Tel.: +48 71 3438675; fax: +48 71 3438150. E-mail address: [email protected] (S. Kozieł). http://dx.doi.org/10.1016/j.jchb.2014.01.003 0018-442X/© 2014 Published by Elsevier GmbH.
A. Skrzek et al. / HOMO - Journal of Comparative Human Biology 65 (2014) 232–239
233
result in a favourable effect on the bones, it rather intensifies negative phenomena in the body resulting in the onset of many diseases. © 2014 Published by Elsevier GmbH.
Introduction It has been indicated that a close relationship exists between obesity and osteoporosis, but it is still unclear whether body fat mass is beneficial or detrimental for bone mass. Some researchers have found that body fat mass ceased to increase bone mass (Kawai et al., 2009; Rosen and Klibanski, 2009), and other multiple studies have found negative correlation between body fat mass and bone mass (Compston et al., 2011; Kim et al., 2012; Yoo et al., 2012). Due to the constant increase of the number of elderly people in a population, these factors are a serious public health problem associated ˛ with fragility fractures (Nielson et al., 2012; Wiacek et al., 2010). The results of considerable research on the preservation of bone mineral density indicate that the body mass index (BMI), aside from menopausal status, is the most important indicator regarding metabolic processes in bone tissue (Bredella et al., 2011; Ho et al., 2008; Park et al., 2010; Reid, 2008; Wilsgaard et al., 2009). Coin et al. (2008) have pointed out that an approximate BMI value of 22 kg/m2 or slightly lower, even though it is within the norm for adults, constitutes a high-risk factor for osteoporosis, particularly in women. This is supported by the strong correlation between BMD (bone mineral density) and BMI. A slim body and the presence of adipose tissue are factors of great relevance for the risk of osteoporosis and fragility fractures. Kim et al. (2010b) have established that a low BMD corresponds to a high concentration of adipose tissue and an extensive hip size, thus, it seems that among the numerous factors related to bone tissue transformation such as lifestyle, body tissue composition and its functional parameters, the BMI is one of the least complicated and the most frequently used indicators significantly related to BMD. Some researchers have reported a substantial relationship between BMI, BMD and fractures in women, however the nature of this correlation is rather U-shaped than linear (De Laet et al., 2005; Johnell et al., 1995; Moayyeri et al., 2012). So far, however, the information on the optimal BMI value, which would correspond to the favourable BMD parameters and the bone structure not being linked with an excessive fat deposition, has been found to be insufficient. An excessive amount of adipose tissue may result in numerous medical conditions that may lead to a higher risk of diabetes, hypertension and other cardiovascular conditions as well as a higher death rate (Dytfeld et al., 2011; Greco et al., 2010; De Laet et al., 2005; Rocha and Libby, 2009; Sukumar et al., 2011; Zoico et al., 2004). The aim of this paper is to establish the optimal values of the BMI which would indicate the most favourable preservation of the bone mineral density in adult women while controlling for their menopausal status.
Materials and methods The material collected consists of the data of 369 healthy women aged between 40 and 88 years (mean age 67.84, SD = 6.70), inhabitants of Wrocław, which were followed up between 2001 and 2006. Bone mineral density was assessed using dual energy X-ray absorptiometry (DEXA) with the DPXplus apparatus (USA) and was first analysed using its specialist software. All measurements were carried out in the Densitometry Laboratory at the Department of Endocrinology and Diabetology of the Medical University in Wrocław. The absolute measure of bone mineral density (BMD) expressed in g/(100 mm2 ) of the femoral neck was used in further analysis. Height and weight were measured by trained staff and BMI was calculated (kg/m2 ). According to the value of BMI, all the women were divided into seven groups beginning with the value 22.0 kg/m2 with a 2-point interval. Postmenopausal status was defined according to the occurrence of menstruation within the last 360 days (Hagner et al., 2009). All women did not experience menstruation, and were assigned with postmenopausal status.
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A. Skrzek et al. / HOMO - Journal of Comparative Human Biology 65 (2014) 232–239
Table 1 Numbers and percentage of women with BMD in norm and with osteopenia and/or osteoporosis by BMI intervals. BMI intervals
BMD in norm N (%)
Osteopenia and/or osteoporosis N (%)
18.0 < x ≤ 20.0 20.0 < x ≤ 22.0 22.0 < x ≤ 24.0 24.0 < x ≤ 26.0 26.0 < x ≤ 28.0 28.0 < x ≤ 30.0 30.0 < x ≤ 32.0 32.0 < x ≤ 34.0 34.0 < x
1 (16.67) 6 (23.08) 22 (31.43) 23 (28.05) 38 (49.35) 33 (51.56) 15 (65.22) 6 (54.55) 7 (70.00)
5 (83.33) 20 (76.92) 48 (68.57) 59 (71.95) 39 (50.65) 31 (48.44) 8 (34.78) 5 (45.45) 3 (30.00)
Table 2 Results of linear multiple regression where BMD was the dependent variable and age, BMI, and menopausal status the independent variables. Multiple R = 0.632; R2 = 0.3996; p < 0.001; error of estimation = 0.846. Variables
Beta
t
p
Age BMI
−0.345 0.337
−7.530 7.372
Contents lists available at ScienceDirect
HOMO - Journal of Comparative Human Biology journal homepage: www.elsevier.com/locate/jchb
The optimal value of BMI for the lowest risk of osteoporosis in postmenopausal women aged 40–88 years A. Skrzek a, S. Kozieł b,∗, Z. Ignasiak a a b
University School of Physical Education in Wrocław, Al. I. Paderewskiego 35, 51-612 Wrocław, Poland Polish Academy of Sciences, Unit of Anthropology in Wrocław, Podwale 75, 50-449 Wrocław, Poland
a r t i c l e
i n f o
Article history: Received 9 May 2012 Accepted 8 January 2014
a b s t r a c t The aim of this paper is to establish the optimal values of the body mass index (BMI) which would indicate the most favourable preservation of the bone mineral density in postmenopausal women. The material consists of the data of 369 healthy women aged between 40 and 88 years (mean age 67.84, SD = 6.70) inhabitants of Wrocław, which were followed up between 2001 and 2006. The absolute measure of bone mineral density (BMD) of the femoral neck was assessed using dual energy X-ray absorptiometry (DEXA), expressed in g/(100 mm2 ) and was transformed to T-score values. According to the value of BMI, the women were divided into eight groups, the reference group with value between 18.0 and 21.9 kg/m2 and seven other groups beginning with the value 22.0 with a 2-point interval. Postmenopausal status was defined according to the occurrence of menstruation within the last 360 days. The women with osteopenia and osteoporosis were pooled together and comprised the risk group, whereas the other women comprised the normal group (T-score values above −1.0). The adjusted odds ratio showed the highest value for intervals between 24.0 and 25.9 units of BMI, and the lowest value for interval 26.0–27.9 units of BMI. The Youden index showed the lowest value in the 26.0–27.9 BMI kg/m2 interval. For our sample the optimal value of BMI, with the lowest risk of osteopenia and/or osteoporosis was the value of 26.9 kg/m2 . A further increase of BMI does not
∗ Corresponding author. Tel.: +48 71 3438675; fax: +48 71 3438150. E-mail address: [email protected] (S. Kozieł). http://dx.doi.org/10.1016/j.jchb.2014.01.003 0018-442X/© 2014 Published by Elsevier GmbH.
A. Skrzek et al. / HOMO - Journal of Comparative Human Biology 65 (2014) 232–239
233
result in a favourable effect on the bones, it rather intensifies negative phenomena in the body resulting in the onset of many diseases. © 2014 Published by Elsevier GmbH.
Introduction It has been indicated that a close relationship exists between obesity and osteoporosis, but it is still unclear whether body fat mass is beneficial or detrimental for bone mass. Some researchers have found that body fat mass ceased to increase bone mass (Kawai et al., 2009; Rosen and Klibanski, 2009), and other multiple studies have found negative correlation between body fat mass and bone mass (Compston et al., 2011; Kim et al., 2012; Yoo et al., 2012). Due to the constant increase of the number of elderly people in a population, these factors are a serious public health problem associated ˛ with fragility fractures (Nielson et al., 2012; Wiacek et al., 2010). The results of considerable research on the preservation of bone mineral density indicate that the body mass index (BMI), aside from menopausal status, is the most important indicator regarding metabolic processes in bone tissue (Bredella et al., 2011; Ho et al., 2008; Park et al., 2010; Reid, 2008; Wilsgaard et al., 2009). Coin et al. (2008) have pointed out that an approximate BMI value of 22 kg/m2 or slightly lower, even though it is within the norm for adults, constitutes a high-risk factor for osteoporosis, particularly in women. This is supported by the strong correlation between BMD (bone mineral density) and BMI. A slim body and the presence of adipose tissue are factors of great relevance for the risk of osteoporosis and fragility fractures. Kim et al. (2010b) have established that a low BMD corresponds to a high concentration of adipose tissue and an extensive hip size, thus, it seems that among the numerous factors related to bone tissue transformation such as lifestyle, body tissue composition and its functional parameters, the BMI is one of the least complicated and the most frequently used indicators significantly related to BMD. Some researchers have reported a substantial relationship between BMI, BMD and fractures in women, however the nature of this correlation is rather U-shaped than linear (De Laet et al., 2005; Johnell et al., 1995; Moayyeri et al., 2012). So far, however, the information on the optimal BMI value, which would correspond to the favourable BMD parameters and the bone structure not being linked with an excessive fat deposition, has been found to be insufficient. An excessive amount of adipose tissue may result in numerous medical conditions that may lead to a higher risk of diabetes, hypertension and other cardiovascular conditions as well as a higher death rate (Dytfeld et al., 2011; Greco et al., 2010; De Laet et al., 2005; Rocha and Libby, 2009; Sukumar et al., 2011; Zoico et al., 2004). The aim of this paper is to establish the optimal values of the BMI which would indicate the most favourable preservation of the bone mineral density in adult women while controlling for their menopausal status.
Materials and methods The material collected consists of the data of 369 healthy women aged between 40 and 88 years (mean age 67.84, SD = 6.70), inhabitants of Wrocław, which were followed up between 2001 and 2006. Bone mineral density was assessed using dual energy X-ray absorptiometry (DEXA) with the DPXplus apparatus (USA) and was first analysed using its specialist software. All measurements were carried out in the Densitometry Laboratory at the Department of Endocrinology and Diabetology of the Medical University in Wrocław. The absolute measure of bone mineral density (BMD) expressed in g/(100 mm2 ) of the femoral neck was used in further analysis. Height and weight were measured by trained staff and BMI was calculated (kg/m2 ). According to the value of BMI, all the women were divided into seven groups beginning with the value 22.0 kg/m2 with a 2-point interval. Postmenopausal status was defined according to the occurrence of menstruation within the last 360 days (Hagner et al., 2009). All women did not experience menstruation, and were assigned with postmenopausal status.
234
A. Skrzek et al. / HOMO - Journal of Comparative Human Biology 65 (2014) 232–239
Table 1 Numbers and percentage of women with BMD in norm and with osteopenia and/or osteoporosis by BMI intervals. BMI intervals
BMD in norm N (%)
Osteopenia and/or osteoporosis N (%)
18.0 < x ≤ 20.0 20.0 < x ≤ 22.0 22.0 < x ≤ 24.0 24.0 < x ≤ 26.0 26.0 < x ≤ 28.0 28.0 < x ≤ 30.0 30.0 < x ≤ 32.0 32.0 < x ≤ 34.0 34.0 < x
1 (16.67) 6 (23.08) 22 (31.43) 23 (28.05) 38 (49.35) 33 (51.56) 15 (65.22) 6 (54.55) 7 (70.00)
5 (83.33) 20 (76.92) 48 (68.57) 59 (71.95) 39 (50.65) 31 (48.44) 8 (34.78) 5 (45.45) 3 (30.00)
Table 2 Results of linear multiple regression where BMD was the dependent variable and age, BMI, and menopausal status the independent variables. Multiple R = 0.632; R2 = 0.3996; p < 0.001; error of estimation = 0.846. Variables
Beta
t
p
Age BMI
−0.345 0.337
−7.530 7.372
