Experimental approaches in the study of pain in the elderly.

The present review summarizes experimental data on age-related changes in pain processing. These data suggest an increase in pain threshold and a decrease in tolerance threshold, which both are dependent on the physical nature of the stressor, as well as a developing deficiency in endogenous pain inhibition, which might be paralleled by an enhanced disposition to central sensitization (stronger temporal summation). These findings are arranged in a model that allows for explaining the two seemingly divergent perspectives: age both dulls the pain sense and increases the prevalence of pain complaints. This model is based on the assumption that both excitatory and inhibitory processes are dampened with age but that the later processes age at a faster rate, leading to increasingly unbalanced pain excitation.