Objectively assessed physical activity and lower limb function and prospective associations with mortality and newly diagnosed disease in UK older adults: an OPAL four-year follow-up study

Background: objective measures of physical activity and function with a diverse cohort of UK adults in their 70s and 80s were used to investigate relative risk of all-cause mortality and diagnoses of new diseases over a 4-year period. Participants: two hundred and forty older adults were randomly recruited from 12 general practices in urban and suburban areas of a city in the United Kingdom. Follow-up included 213 of the baseline sample. Methods: socio-demographic variables, height and weight, and self-reported diagnosed diseases were recorded at baseline. Seven-day accelerometry was used to assess total physical activity, moderate-to-vigorous activity and sedentary time. A log recorded trips from home. Lower limb function was assessed using the Short Physical Performance Battery. Medical records were accessed on average 50 months post baseline, when new diseases and deaths were recorded. Analyses: ANOVAs were used to assess socio-demographic, physical activity and lower limb function group differences in diseases at baseline and new diseases during follow-up. Regression models were constructed to assess the prospective associations between physical activity and function with mortality and new disease. Results: for every 1,000 steps walked per day, the risk of mortality was 36% lower (hazard ratios 0.64, 95% confidence interval (CI) 0.44-0.91, P = 0.013). Low levels of moderate-to-vigorous physical activity (incident rate ratio (IRR) 1.67, 95% CI 1.04-2.68, P = 0.030) and low frequency of trips from home (IRR 1.41, 95% CI 0.98-2.05, P = 0.045) were associated with diagnoses of more new diseases. Conclusion: physical activity should be supported for adults in their 70s and 80s, as it is associated with reduced risk of mortality and new disease development.