The aim of this study was to evaluate the effects on diabetic peripheral neuropathy (DPN) of a long-term intensive lifestyle intervention (ILI) programme designed to achieve and maintain weight loss.
Beginning in 2001, a total of 5145 overweight or obese people with type 2 diabetes, aged 45-76 years, participating in the multicentre Look AHEAD (Action for Health in Diabetes) study were randomised to ILI (n = 2570) or to a diabetes support and education (DSE) control group (n = 2575) using a web-based management system at the study coordinating centre at Wake Forest School of Medicine (Winston-Salem, NC, USA). Randomisation was stratified by clinical centre and was not revealed to the clinical staff responsible for obtaining data on study outcomes. Because of the nature of the study, patients and the local centre interventionists were not blinded to the study group assignments. In addition, the coordinating centre staff members responsible for data management and statistical analyses were not blinded to the study group assignments. The interventions were terminated in September 2012, 9-11 years after randomisation, but both groups continued to be followed for both primary and secondary outcomes. Neuropathy evaluations included the Michigan Neuropathy Screening Instrument (MNSI) questionnaire completed at baseline in 5145 participants (ILI n = 2570, DSE n = 2575) and repeated annually thereafter and the MNSI physical examination and light touch sensation testing conducted in 3775 participants (ILI n = 1905, DSE n = 1870) 1-2.3 years after discontinuation of the intervention.
At baseline, the MNSI questionnaire scores were 1.9 ± 0.04 and 1.8 ± 0.04 in the ILI and DSE groups, respectively (difference not statistically significant). After 1 year, when weight loss was maximal in the ILI group (8.6 ± 6.9%) compared with DSE (0.7 ± 4.8%), the respective MNSI scores were 1.7 ± 0.04 and 2.0 ± 0.04 (p ≤ 0.001). Subsequently, the scores increased gradually in both groups, but remained significantly lower in the ILI group for the first 3 years and at the end of follow-up. In both groups, there was a significant association between changes in the MNSI scores and changes in body weight, HbA1c and serum lipids. There were no significant between-group differences in the proportions of participants with MNSI physical examination scores ≥2.5, considered to be indicative of diabetic neuropathy. The light touch sensation measured separately in either the right or left big toes (halluces) did not differ between ILI and DSE, but when the data were combined for both toes, light touch was better preserved in the ILI group.
ILI resulted in a significant decrease in questionnaire-based DPN, which was associated with the magnitude of weight loss. In both the ILI and DSE groups, changes in the MNSI score were also related to changes in HbA1c and lipids. There were no significant effects of ILI on physical examination measures of DPN conducted 1-2.3 years after termination of the active intervention, except for light touch sensation, which was significantly better in the ILI group when measurements were combined for both toes. However, a potential limiting factor to the interpretation of the physical examination data is that no baseline studies are available for comparison.
This work was funded by the National Institutes of Health through cooperative agreements with the National Institute of Diabetes and Digestive and Kidney Diseases.