Effect Of Type 2 Diabetes Mellitus On Bone Mineral Density (BMD) In Middle-Aged Black South African Women

Abstract

Diabetes mellitus is a serious medical condition that occurs when the body cannot utilise glucose normally. There are two main types of diabetes, known as type 1 diabetes mellitus and type 2 diabetes mellitus. Type 2 diabetes mellitus is the most common type of diabetes which can have serious complications if not treated. Osteoporosis/osteopenia (low bone mass) are hidden, major health concerns for our society as a result of their quiescence nature of the bone loss process with no signs or symptoms until a fracture occurs. Non-invasive bone densitometry utilising X-ray absorptiometry enables accurate evaluation of bone mass and the diagnosis of osteoporosis in asymptomatic individuals prior to fracture. Bone mineral density is a vital component in the diagnosis and management of osteoporosis regarding bone strength, since fracture risk increases exponentially as bone mineral density decreases. A DXA scan was performed on each subject. The sites used in this study included the femoral neck (left and right), total hip (left and right) and the AP lumbar spine. This was a retrospective study. Data of 140 Black female subjects were obtained from a database. Ninety-one subjects were previously diagnosed with type 2 diabetes mellitus and acted as the test group, whilst 49 subjects had no diagnosis of diabetes mellitus and acted as the test group. The T-scores of the test group and the control group were compared according to the guidelines of the World Health Organization. These two groups were further divided into two subgroups according to age, as proposed by the National Osteoporosis Foundation of South Africa. Subjects ≥ 50 years were added in the calculations for the T-score, whilst subjects < 50 years were added in the calculations for Z-score. The aim of this study was to address the effect of type 2 diabetes mellitus on bone mineral density in middle-aged Black South African women. A literature review was conducted to identify data sources for this ethnic group. Statistical analysis was used to determine whether numerical variables followed a normal distribution pattern. Numerical values used included age, height, weight, BMI, T-score, Z-score and BMD. Descriptive statistics (means and standard deviations and percentiles) were used to calculate for numerical data, whilst frequencies and percentages were calculated for categorical data. The test and control groups were compared with calculations from the independent T-test to test for differences between mean values, whilst the Mann Whitney-U test was used to identify differences between the median values. A significance level (α) of 0.05 was used, where p≥0.05 indicates no significant difference in the mean or median values of the two groups, and p< 0.05 indicates significant differences. Fisher’s exact test was used to compare percentages of the T-score and Z-score in the two groups with the same significant level (α) p 0.05 to determine the difference between the proportions of the two groups. The results of the test group compared with the control group according to the WHO definition of diagnosis with regards to the T-score showed no significant difference in the bone mineral density in the different areas. Osteopenia was more prevalent than Osteoporosis in both groups. The results of the subjects ≥50 years’ T-score diagnosis according to the NOFSA guidelines indicate no significant difference between the proportions of the two groups, accept at the right femoral neck. There was no significant difference between the proportions of the two groups at the Z-score for women < 50 years. Although the difference was not statistically significant between the T-score, Z-score and BMD between the two groups, there is evidence of low bone mass (osteopenia) in general for this population. It has been observed that type 2 diabetes mellitus negatively affects bone strength, regardless of bone mineral density. Furthermore, diabetes mellitus is a risk factor for osteoporosis and fractures, and that fractures can occur at higher bone mineral density levels in patients with diabetes mellitus.