Chronoscopic reading in whole body reaction times can be a tool in detecting cognitive dysfunction in hypothyroidism: a case-control study

Abstract

Background: Hypothyroidism investigated as a risk factor for cognitive decline. It is known that difference between simple and choice reaction time (RT) implies time required for cognition. Though delayed RTs indicate involvement of cognition, they cannot quantify how much time is required for cognition. In whole body choice reaction time (WBCRT), RT is split into two chronoscopic readings, Chronoscope-1 (C1) and Chronoscope-2 (C2). C1 measures time required for central processing, which requires cognition and C2 measures total RT. C2-C1 measures time required for the peripheral motor response. We hypothesized that WBCRT C1will be delayed in hypothyroidism, and WBCRT C1 will have predictive value in detecting cognitive dysfunction. Settings and Design: Hospital based case control study. Materials and Methods: Study was conducted on 99 subjects using visual and whole body reaction timers having criteria of age (20-60years) and hypothyroidism, compared with an equal number of age and sex matched controls. Statistical analysis was done by Independent t-test and duration of hypothyroidism was correlated with cognition times (WBCRT C1) using Pearson’s correlation. Predictive value of WBCRTC1 was calculated by using receiver operating characteristic curve. Results: Delayed visual simple reaction time (VSRT), Visual choice reaction time (VCRT), Whole body simple reaction time (WBSRT), and WBCRT observed among subjects of hypothyroidism when compared with controls. Choice RTs were more delayed compared to simple RTs. WBCRT C1 (578±110 ms) was more delayed than WBSRT C1 (396 ± 87.1 ms) among hypothyroid patients indicating cognitive dysfunction. There was no significant correlation between duration of hypothyroidism with cognition. The best cut-off value for WBCRTC1, when predicting cognitive dysfunction in hypothyroidism was 527 ms. (sensitivity 48% specificity 40.8%). Conclusions: WBCRT C1 can be used as a tool to detect cognitive dysfunction.