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 Table of Contents  
ORIGINAL ARTICLE
Year : 2015  |  Volume : 29  |  Issue : 2  |  Page : 69-73

Chronoscopic reading in whole body reaction times can be a tool in detecting cognitive dysfunction in type 2 diabetics: A case control study


1 Department of Physiology, SDM College of Medical Sciences, Dharwad, Karnataka, India
2 Department of General Medicine, SDM College of Medical Sciences, Dharwad, Karnataka, India
3 Department of Psychiatry, SDM College of Medical Sciences, Dharwad, Karnataka, India

Date of Web Publication20-Aug-2015

Correspondence Address:
Vitthal Khode
Department of Physiology, SDM College of Medical Sciences, Sattur, Dharwad, Karnataka
India
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Source of Support: None, Conflict of Interest: None


DOI: 10.4103/0972-4958.163188

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  Abstract 

Background: Type 2 diabetes mellitus investigated as a risk factor for cognitive decline. It is known that the difference between simple and choice reaction time implies time required for cognition. Though delayed reaction times indicate involvement of cognition, they cannot quantify how much time is required for cognition. In whole body choice reaction time (WBCRT), reaction time is split into two chronoscopic readings: Chronoscopic reading-1 (C1) and chronoscopic reading-2 (C2). C1 measures time required for central processing that requires cognition and C2 measures the total reaction time. C2 - C1 measures time required for peripheral motor response. We hypothesized that WBCRT C1 will be delayed in diabetes and will have predictive value in detecting cognitive dysfunction. Settings and Design: Hospital-based case control study. Materials and Methods: Study was conducted on 120 subjects using visual and whole body reaction times having criteria of age (40-60 years) and diabetes, compared with equal number of age- and sex-matched controls. Statistical analysis was done by independent t-test and duration of diabetes was correlated with cognition times (WBCRT C1) using Pearson's correlation. Predictive value of WBCRT C1 was calculated by using the receiver operating characteristic (ROC) curve. Results: WBCRT C1 (564 ± 107 ms) among diabetes patients was more delayed than WBCRT C1 (513 ± 86 ms) among controls indicating a cognitive dysfunction in patients with diabetes. There was no significant correlation between hemoglobin A1c (HbA1c) levels in patients with diabetes and diabetic duration with WBCRT C1. The best cutoff value for WBCRT C1, when predicting cognitive dysfunction in patients with diabetes, was 517 ms (sensitivity 50%, specificity 40%). Conclusions: WBCRT C1 can be used as a tool to detect cognitive dysfunction in patients with type 2 diabetes mellitus.

Keywords: Cognition, Reaction times, Type 2 diabetes mellitus (DM), Whole body choice reaction time chronoscopic reading 1 (WBCRT C1)


How to cite this article:
Khode V, Sindhur J, Ramdurg S, Ruikar K, Nallulwar S. Chronoscopic reading in whole body reaction times can be a tool in detecting cognitive dysfunction in type 2 diabetics: A case control study. J Med Soc 2015;29:69-73

How to cite this URL:
Khode V, Sindhur J, Ramdurg S, Ruikar K, Nallulwar S. Chronoscopic reading in whole body reaction times can be a tool in detecting cognitive dysfunction in type 2 diabetics: A case control study. J Med Soc [serial online] 2015 [cited 2020 Oct 20];29:69-73. Available from: https://www.jmedsoc.org/text.asp?2015/29/2/69/163188


  Introduction Top


Type 2 diabetes mellitus (DM) is a common disease among the elderly people and has been associated with central and peripheral neuronal degeneration that causes cognitive impairment, dementia, [1],[2],[3],[4],[5],[6] and peripheral neuropathy. All of these cause delay in reaction times (RTs). RT is a reliable indicator of the time taken from onset of stimulus to an appropriate response that includes rate of processing of sensory stimuli by central nervous system and its execution by motor response. It is known that the difference between simple and choice reaction time implies cognitive dysfunction. [7],[8] Investigators have shown that choice reaction times are delayed in patients with diabetes. [9],[10] Although delayed reaction times indicate involvement of central processing, they cannot quantify how much time is required for central processing.

In whole body choice reaction time (WBCRT), reaction time is split into two chronoscopic readings WBCRT chronoscopic reading-1 (C1) and WBCRT chronoscopic reading-2 (C2). WBCRT C1 is the time required from the start of visual stimuli to the time the subject lifts his leg from the starting platform, which measures time required for central processing or cognition. WBCRT C2 is the time required from the start of visual stimuli to the end of response. WBCRT C2 - C1 is the time required for peripheral response. The purpose of our study is to measure WBCRT C1 in diabetics without overt cerebrovascular disorder, or target organ damage, or other vascular risk factors and compare them with age- and sex-matched controls to detect cognitive dysfunction in patients with diabetes. Our aim was also to correlate duration of diabetes and hemoglobin A1c (HbA1c) in patients with diabetes with WBCRT C1. We tried to find the predictive value of WBCRT C1 in detecting cognitive dysfunction in patients with diabetes.


  Materials and Methods Top


After getting the approval from the Institutional Ethics Committee, this case control study was carried out over 6 months (August 2010-January 2011) with purposive sample with the criteria of age and diabetes. The samples were selected from the outpatient department (OPD) of medicine of our institution. One hundred and twenty individuals participated in the study. The whole study population was divided into two groups. Group 1 consisted of randomly selected clinically diagnosed patients with diabetes with more than 2 years of duration aged between 40 years and 60 years. Group 2 consisted of randomly selected sex- and age-matched controls selected from the college staff and subjects attending the medical OPD for routine checkup. Sample size was determined by standard error of test obtained by the pilot study. Each individual was briefed about the study, its importance and procedural details, and written consent was taken from him or her before recording the various reaction times. In both the groups following subjects were excluded from the study: Patients of hypertension, overt cardiovascular disorders, cerebrovascular disorders, neuropathy, chronic renal disorders and smokers. We also excluded patients having chronic lower back pain or spasms; deformities of the spine, bones, or joints (including advanced arthritis); spinal cord injuries or other damage to the nervous system; nonhealing skin ulcers; current drug or alcohol dependence. Individuals taking any prescription medicine to prevent dizziness were also excluded. The basic parameters and detailed history were recorded. During general checkup pulse rate, blood pressure, height, weight, food habits, and exercise pattern were recorded. Ophthalmic evaluation was done by using Snellen and Jaeger chart.

According to the Indian Council of Medical Research (ICMR) guidelines (2005), DM was diagnosed on the basis of the following criteria:

  1. Fasting blood sugar (FBS) level > 126 mg/dL,
  2. Postprandial blood sugar (PPBS) level > 200 mg/dL of patients on antidiabetic therapy.


HbA1c, FBS, and PPBS levels were measured. HbA1c was estimated in whole blood, by the ion-exchange resin method. The optical density of each proportion was measured spectrophotometrically on semiautomated chemistry analyzer, Microlab 200, followed by an evaluation of the relative proportion of HbA1c with respect to total HbA. Plasma samples of the same patients were analyzed on fully automated chemical pathology analyzer, Selectra E, for the estimation of plasma glucose levels, by enzymatic (glucose oxidase) colorimetric method.

Equipment used for reaction times:

The reaction times:

A. Visual reaction time:

  1. Visual simple reaction time (VSRT).
  2. Visual choice reaction time (VCRT).


B. Whole body reaction time.

  1. Whole body simple reaction time (WBSRT).

    (C1, C2, and C2 - C1).
  2. WBCRT.

    (C1, C2, and C2 - C1).


Anand Agencies, Pune manufacturer of research tool reaction time apparatus, with chronoscope compartment showing time in ms.

Procedure

After brief instructions, three trials for each of VSRT, VCRT, WBSRT, and WBCRT were given and the individual reaction time in ms was recorded five times in both diabetic patients and controls. An attempt was made to obtain at least five acceptable recordings for each participant. Measurements of the VSRT, VCRT, and WBSRT were considered reproducible if the difference between maximum and minimum values did not exceed 50 ms. Reliability of the test was calculated based on the data obtained by the pilot study. Coefficient of correlation for VSRT was 0.927 with α error was 0.9844. VSRT: The subject is instructed to press the right button as soon as red light glows and chronoscopic reading is recorded. VCRT: The subject is instructed to press the left button when green light glows and the right button when red light glows and reaction time is recorded. WBSRT: The subject standing on the starting board is instructed to watch the glowing arrow and to step one leg on the stepping board in a single direction. WBSRT C1 gives time taken for lifting of the foot from the onset of the stimulus, WBSRT C2 gives the total time required for placing the foot on the stepping board from the onset of stimulus, and WBSRT C2 - C1 gives the movement time from starting board to stepping board, that is, the time taken for motor activity. WBCRT: The subject is asked to move either of the legs according to the direction of glowing arrow to right, front, left, behind, and right again, which involves more cognition compared to WBSRT, WBCRT C1, WBCRT C2, and WBCRT C2 - C1 mean same as that of WBSRT.

Statistical analysis

The results were tabulated separately and statistical results are presented as mean ± standard deviation (SD). The Statistical Package for the Social Sciences (SPSS) version 16 (SPSS-Inc., Chicago, US) software analyzer was used. The data were analyzed by independent t-test that indicates the level of difference between groups, with significance at 5% level using t-statistic, that is, P values <0.05. Pearson's correlation was performed to find the correlation between duration of diabetes and HbA1c levels in patients with diabetes and WBCRT C1. To determine the accuracy and respective best cutoff values of WBCRT C1 for predicting cognitive dysfunction in patients with diabetes, the receiver operating characteristic (ROC) curves and their corresponding areas under the curve (AUC) were used. A P value of <0.05 was considered statistically significant.


  Results Top


As per [Table 1], there was no significant difference in age. The mean age of controls was 51.3 years and that of diabetics was 52.5 years. There were 18 females in groups 1 and 2. There was no significant difference between reaction times among male and females. [Table 1] also shows mean of measured values of FBS and PPBS. There was no significant difference in these parameters. The mean value of HbA1c in patients with diabetes was 8.18 ± 0.93%.
Table 1: Demographic variables of diabetics and controls

Click here to view


Significant delayed VSRT, VCRTs were observed in patients with diabetes compared to controls with P-values 0.007 and 0.020, respectively. Choice reaction times were more delayed. WBSRT C2 and WBSRT C2 - C1 were delayed in patients with diabetes compared to controls and were statistically significant (P values = 0.010 and 0.003, respectively). WBCRT C1, WBCRT C2, and WBCRT C2 - C1 were delayed in patients with diabetes compared to controls and were statistically significant (P values = 0.005, 0.000, and 0.007, respectively). Choice reaction times were more delayed than simple reaction times. WBCRT C1 was more delayed compared to WBSRT C1 [Table 2]. There was no significant correlation between duration of diabetes (average 4.78 years) and HbA1c levels in patients with diabetes and WBCRT C1 (r = 0.029, P = 0.827). There was significant correlation between duration of diabetes and HbA1c levels (r = 0.515, P = 0.000). There was no significant correlation between HbA1c levels and WBCRT C1 in diabetics (r = 0.014, P = 0.915). ROC curve of WBCRT C1 when predicting cognitive dysfunction in patients with diabetes was constructed and the AUC was found to be 0.371 (95% CI, lower bound 0.272, upper bound 0.471) statistically significant (P = 0.015). The best cutoff value of WBCRT C1, when predicting cognitive dysfunction in patient with diabetes, was 517 ms (sensitivity 50%; specificity 40%).
Table 2: Comparison of reaction times among diabetics and controls

Click here to view



  Discussion Top


We observed that reaction times were delayed in patients with diabetes. WBCRT C1 was significantly delayed in patients with diabetes compared to controls which indicates involvement of cognition. We found that WBCRT C1 could be predictive of cognitive dysfunction in patients with diabetes.

There are several limitations of this study. Although controls were age and sex matched, their body mass indices (BMIs) were not matching. It is known that BMI affects cognition. Another limitation of our study was that we did not perform gold standard test that could identify cognitive dysfunction so that we could compare our findings and assess sensitivity and specificity of the test. These batteries of tests are considered gold standard as they evaluate multiple aspects of cognition. However, batteries of tests are time-consuming and require skilled staff. On the contrary, reaction times can be easily performed on OPD basis. They can be sensitive indicators of cognitive dysfunction especially attention and psychomotor speed. Therefore, the strength of our study was that we could use WBCRT C1 as a screening tool for early detection of cognitive dysfunction in patients with diabetes.

Type 2 DM is known to cause cognitive dysfunction and peripheral neuropathy. Both of these cause delay in reaction time. Many studies using neuropsychological batteries of tests have shown that diabetes affects cognition. [11],[12] Some studies on patients with diabetes have indicated decline in certain cognitive domains [13] such as verbal memory, attention and executive functions, and visual retention/visual working memory [14] despite some negative results. Cross-sectional comparisons of 52 diabetics with matched controls and with 610 controls (covaried for age and education) found no group differences and no support for an accelerated cognitive aging effect of diabetes. In addition, longitudinal comparisons over 6 years and over 12 years found no effect of diabetes on cognitive performance. [15] Numerous nerve conduction studies have been done to prove that diabetes causes conduction abnormalities secondary to peripheral neuropathy. [16],[17] Reaction time measurement includes the latency in the sensory neural code traversing peripheral and central pathways; perceptive, cognitive, volitional processing. In choice reaction time, time required for central processing increases, whereas time required for peripheral response does not alter much. At this point, we require a tool that clearly measures the time required for central processing and peripheral processing in total reaction time. Many studies shown delay in visual and auditory simple and choice reaction times in diabetes. [9],[10] However, they have failed to explain whether the delay was because of central processing or time taken for peripheral response. In our study along with visual simple and choice reaction times, we have measured WBSRT and WBCRT in which WBCRT C1 apparently measures the time required for perception and cognition, the time taken for lifting the foot from starting board, from onset of stimulus. WBCRT C2 measures apparently motor signal traversing both central and peripheral neuronal structures, the total time required for placing the foot on stepping board from onset of stimulus. Therefore, it becomes easy to tease out central effect versus peripheral effects when reaction times are slowed. Our aim of the study was to measure WBCRT C1 in patients with diabetes and compare it with controls that approximately ststes the difference in cognition between these two groups. We hypothesized that WBCRT C1 could be a screening tool used to detect cognitive dysfunction.

In the present study, visual reaction times are delayed in diabetes. Choice reaction times were more delayed which indicates that cognition is affected. Both WBCRT C1 and WBCRT C2 were delayed in diabetics which indicates that there is involvement of both the central processing, that is, cognition and peripheral response. WBCRT were more delayed than WBSRT in diabetes which again indicates that cognition is involved.

Whole body reaction times were delayed to a greater extent in patients with diabetes compared to visual reaction times. Therefore, we could say whole body reaction time measurement was more sensitive. There was no significant correlation between HbA1c levels and WBCRT C1 in patients with diabetes. The reason could be, all diabetic patients were on antidiabetic therapy, and HbA1c indicates levels of glucose in blood in the past 3 months. [18] There was no significant correlation between WBCRT C1 and duration of diabetes, because most of the patient's diabetic duration was less than 5 years and all were receiving antidiabetic therapy.

There are no systemic review implicating reaction times, especially WBCRT C1, for detecting cognitive dysfunction. WBCRT C1 can apparently measure time required for cognition if not accurately. This study may provide platform for further studies in this direction particularly underlying mechanisms with properly matched controls.

From this study, we can conclude that diabetes does affect reaction time, and severity of slowing may be related to difficulty of the task and prevalence of central and peripheral nerve deficits seen as side effects of diabetes. Auditory, visual reaction times the simplest of tasks with shortest path between peripheral and central nervous system showed less delayed reaction times. Choice visual reaction time showed more delayed reaction time because of involvement of complicated circuits. When a more complicated task was included as in whole body reaction time, significant difference was seen in reaction time and with WBCRT the difference further increased. This difference was attributed to cognition. In WBCRT with C1 and C2 - C1, probably it is possible to say how much of time is required for central processing and for motor response.

Financial support and sponsorship

Nil.

Conflicts of interest

There are no conflicts of interest.

 
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