Effects of age, gender, height, and weight on late responses and nerve conduction study parameters

Background: Different methods in performing nerve conduction studies (NCS) yield different results. The results of NCS can also be affected by factors such as gender, age, height, and weight. This study aimed (1) to survey the effects of such factors, (2) to determine the importance of these factors, and (3) to analyze them for building equations in NCS and late response studies. Methods: NCS from the neurological screening tests of 101 individuals without spinal cord, root, nerve, neuro-muscular junction, muscular, or systemic diseases were collected and analyzed. Results: Subjects with older age had longer latencies, smaller amplitudes, and slower velocities compared with those in the younger age group. The change with age was greater in the median than in the ulnar nerve. Female subjects or those with lower weight had higher median and ulnar sensory amplitude. Females had shorter latency in the upper limbs and longer latency in the lower limbs by F-wave studies than males did. Height was an important factor by F-wave studies, with approximately 0.1 ms/cm and 0.3 ms/cm increase in the upper and lower limbs, respectively. Height and age were the most significant factors in the H reflex study with an increase of 0.18 ms/cm in height and 0.07 ms/year in age. Conclusion: Without adjustment for these factors, the sensitivity and specificity of NCS will decrease when using the same reference data in patients with different gender, age, height, and weight.