Review of target trial emulation on diet and activity in older adults

The 2019 Canada's Food Guide (CFG) may not be tailored for older adults, since it provides universal recommendations. In community-dwelling adults aged 67-84 years and compared with habitual diet and physical activity, our objective was to estimate the 3-year difference in muscle strength, physical function, cardiometabolic health and cognitive health score according to adherence to CFG recommendations (CFG), enhancements with additional protein foods (CFG-PRO), physical activity (PA) and both (CFG-PLUS). Longitudinal non-experimental data from the NuAge study (2003-2008 in Quebec, Canada) were used to emulate a 3-year target trial. Data was collected at annual in-person follow-up visits. The hypothetical interventions were modelled using the parametric g-formula assuming no unmeasured confounding, no measurement error and correct models. 1561 participants were eligible. Compared with no intervention, adherence to the CFG intervention would have increased quadriceps strength by 0.8 kg (95%CI: 0.0, 1.7), walking speed by 0.03 m/s (95%CI: 0.00, 0.05) and reduced waist circumference by 1.0 cm (95%CI: -1.7, -0.3). Estimates were similar for the CFG-PRO intervention. Compared with CFG alone, the CFG-PLUS intervention improved to a greater extent walking speed (vs. CFG, +0.06 m/s; 95%CI: 0.03, 0.08) and waist circumference (vs. CFG, -0.8 cm; 95%CI: -1.5, -0.2). Under strong assumptions, compared with no intervention leading to declines in most outcomes, adherence to CFG recommendations over 3 years would have attenuated declines in strength and walking speed in older adults. Greater benefits were achieved when protein food intake and physical activity were increased in addition to CFG adherence.