Aging and physical function in type 2 diabetes: 8 years of an intensive lifestyle intervention

Type 2 diabetes mellitus (T2DM) is a serious threat to public health both in the United States (1,2) and globally (3). T2DM is largely a disease of obesity and aging (4), and its prevalence is expected to increase in the United States over the next two decades as a result of our overweight and aging population (5,6). The combined effect of T2DM and aging on physical functioning (PF) threatens independence of older adults (7), compromises glucose storage and clearance via loss of muscle mass (8), and reduces quality of life (9). Existing data reinforce the public health significance of this problem, in that older adults with T2DM have twice the prevalence of physical disability as those without the disease (10), and the severity of obesity further increases this risk (11). In the Look AHEAD study, a large multicenter trial examining the effects of an intensive lifestyle intervention (ILI) on cardiovascular events in T2DM, the first 4 years of the ILI treatment led to a 48% reduction in limitations with specific mobility-related activities compared with diabetes support and education (DSE) (12). In addition, across the first 8 years of the study, participants in the ILI treatment had higher scores on the SF-36 composite index for physical health than those in DSE (13). The current study is a secondary data analysis of 8 years of data within Look AHEAD that examines self-reported PF using the 10-item subscale from the SF-36 composite physical health index. Although we first examine treatment differences between ILI and DSE, and expected to find that ILI would have higher PF than DSE, our primary goal was to examine whether age or history of cardiovascular disease (CVD) at enrollment moderated these treatment effects. Published results from both the Diabetes Prevention Program (14) and Look AHEAD (15) would suggest that older participants should derive more benefit in PF from the ILI treatment than younger participants. Also, based on the published results for the primary outcome paper in Look AHEAD (16), we anticipated that preexisting CVD would mitigate the benefit from ILI compared with those without preexisting CVD and that the decline in PF across time would be greater for participants with than participants without CVD.