Low lumbar spine bone mineral density in both male and female endurance runners
Introduction
Since the early 1980s, many studies have confirmed the problem of low bone mineral density (BMD) in highly trained female athletes, particularly in endurance runners, and this evidence continues to accumulate. Cross-sectional studies report between 3 and 24% lower BMD in highly trained female runners compared to age-matched controls [1], [2], [3], [4] and longitudinal studies report significant bone loss over 2 to 10 years in female runners [5], [6]. There is some evidence for low BMD in male runners [7], [8], [9], [10], [11], although this has received relatively little attention, despite the recognition that 1 in 5 men will suffer from osteoporosis in their lifetime [12].
Suggested risk factors for low BMD in female athletes include exercise-induced amenorrhea (absence of menses), disordered eating and low body weight. Although estrogen deficiency was once presumed the underlying cause [1], [2], [3], [4], [5], [6], [13], it is now established that energy deficiency (arising from disordered eating or simply an insufficient energy intake to match expenditure [14], [15]), is the driving factor for bone loss and low BMD in this population [16]. Of interest, animal studies indicate that exercise-induced menstrual irregularity and the associated estrogen deficiency are secondary to energy deficit [17]. In male runners, low BMD appears to be unrelated to levels of sex hormones [8], [9], [10], but short-term energy deficiency has been shown to suppress bone formation in male athletes [18].
To date, no studies have compared BMD in male and female runners; thus, the hypothesis that low BMD in athletes should only be of significant concern for females has not yet been tested. In light of this, we aimed to compare BMD between male and female runners and with a reference population. This would seem an important starting point from which further studies can investigate potential factors associated with BMD in athletes, which may or may not be sex-specific.
Section snippets
Materials and methods
All eligible subjects provided signed informed consent and participated in the study conducted in accordance to the principles in the Declaration of Helsinki and with approval from the Leeds (West) Research Ethics Committee.
Male and female endurance runners aged 19 to 50 years were recruited by a national athletics magazine advertisement, word of mouth and posters at athletic clubs, universities and competition venues throughout the UK. The majority of peak bone density accrual has occurred by
Results
Table 1 gives the results data for all variables and differences in measurements between male and female runners. Male subjects ran further distances per week than females (P < 0.05), ranging from 32 to 187.2 km in males and 32 to 152 km in females.
Sex-specific T scores for BMD were comparable in male and female runners (lumbar spine f = 0.015; P = 0.904; total hip f = 0.192; P = 0.662; femoral neck f = 0.205; P = 0.651). In both sexes, lumbar spine T scores were statistically lower than zero (P
Discussion
While it is established that female runners with menstrual irregularity face a bone threat [1], [2], [3], [4], [5], [6], there is less of a consensus that male runners are also at risk. We found significantly lower lumbar spine BMD in male runners compared to reference values, with over one third of the group having low BMD. Interestingly, we also found lower lumbar spine T scores in male runners compared to female eumenorrhoeic runners, to a level indifferent to that of oligoamenorrhoeic
Acknowledgments
This study was supported by a University of Leeds PhD scholarship.
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