Grip strength affects the association between platelet count and disability-free survival: Evidence from the China Health and Retirement Longitudinal Study

•A large prospective study on 6252 middle-aged and older Chinese.•First study to prospectively compare the association between platelet count and disability-free survival among middle-aged and older Chinese with different levels of grip strength.•An inverse dose-response association of platelet count with disability-free survival was found among participants with normal grip strength, but not among those with low grip strength. Previous studies found elevated platelet count (PLT), especially long-term persist high or increased PLT was associated with less likelihood disability-free survival (DFS). However, whether grip strength affects the relationship between them is still not elucidated. A total of 6252 participants were recruited in the analysis based on the China Health and Retirement Longitudinal Study. The primary outcome was DFS, evaluated by a composite endpoint based on the first occurrence of either disability (having difficulty in at least one of the 6 activities of daily living: namely, dressing, bathing, continence, eating, getting into or out of bed, and toileting) or all-cause mortality. The association of PLT with primary outcome was significantly modified by grip strength (pinteraction = 0.022). The rates of primary outcome were significantly lower among participants with lower baseline PLT in participants with normal grip strength (multivariable odds ratio [OR], 0.67; 95% confidence interval [CI], 0.54–0.84; ptrend < 0.001), but not in those with low grip strength (multivariable OR, 1.70; 95% CI, 0.88–3.15; ptrend = 0.135), for the lowest quartile vs the highest quartile. Adding baseline PLT (quartiles or continuous) to a model containing conventional risk factors significantly improved risk reclassification for primary outcome among those with normal grip strength (most of p < 0.05). An inverse dose-response association of PLT with DFS was found among participants with normal grip strength, but not among those with low grip strength. Low grip strength might weaken the benefit of low PLT on DFS among middle-aged and older Chinese.