Bilateral traits in the human body are generally symmetric. A composite of deviations from this bilateral symmetry is known as fluctuating asymmetry (FA). Increased FA has been associated with negative health outcomes and developmental disorders and is used as a measure of developmental instability (DI). In a previous study from our laboratory, FA was found to be significantly higher in patients with type 2 diabetes mellitus (DM2) than in controls. This raised the possibility that measures of DI may predict susceptibility to adult DM2. However, the earlier study did not address the possibility that the disease process may have led to the increased FA. To explore this question, we looked at the asymmetry of the hand and lower arm in DM2 patients in relation to duration and severity of the disease. We examined 41 patients between the ages of 18 and 60 with DM2 in four medical facilities and measured six factors: wrist width, ulnar length, hand width and hand length, and digit 2 and digit 4 (D2, D4) lengths. By questionnaire we assessed the severity of disease by looking at four aspects of DM2: insulin use, medication changes, hospitalization related to DM2, and presence of diseases secondary to DM2. We hypothesized that the correlation between disease and FA from the previous study was due to the disease causing the asymmetry rather than to the asymmetry representing a predisposition for the disease. Comparing the FA in patients with different severity levels of DM2, we found no significant relationship (p = .4168), that is, there is no increase in FA with increasing severity, suggesting that the disease did not cause the asymmetry. We also looked at increasing length of illness and found no significance with FA (p = .1677), showing that FA is not dictated by how long a patient has had the disease. The results of this study support the previous study and suggest that DM2 patients may have increased DI earlier in life that predisposes them to the disease.
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