Diabetics and Reaction Times: Cause for Concern

Edited excerpts from the article “A comparative study of reaction times between type II diabetics and non-diabetics” by Samantha J Richerson, Charles J Robinson and Judy Shum

Editing and Commentary by Dr. Don Rose, Writer, Life Alert

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An article of mine found elsewhere on this Senior Protection site discusses falls among seniors. In it, I hope to convey some of the common causes of falls, and their prevention. One of the causes is slower reaction times that develop in the elderly. In the article by Richerson, Robinson and Shum (excerpted below), the authors detail a study comparing Type II diabetics and non-diabetics. One of their conclusions is that slips and falls are more likely to occur among the diabetic group, due to increased reaction times. Since an increasing number of Americans are developing Type II diabetes, often due to obesity, there is much cause for concern. Seniors who are diabetic are doubly at risk, since they are in two risk groups for slower reaction times.

However, knowledge is power. Use the information below as motivation, and ammunition, to take the steps needed to prevent or even reverse Type II diabetes. The cascade of beneficial effects will be enormous. --Dr. Don Rose

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Introduction and Background

Aging slows reflexes and increases the time to react to a number of external stimuli of different modalities. What has escaped extensive examination has been the effect of Type II diabetes on these same reaction times and the comparison of modalities across the various sensory inputs. Only two studies have tested older individuals with diabetes. These have demonstrated increased reaction times to visual and auditory stimuli. Mohan, et al. found a 30 ms difference in auditory reaction times between those with diabetes (approximately 210 ms) and a control group (180 ms). Dobrzanski, et al. found a doubling of visual reaction time in diabetics (473 ms) versus that measured in healthy individuals (216 ms). In addition to the measured effects in these two studies, diabetes has also been shown to affect peripheral nerves in the somatosensory and auditory system, slows psychomotor responses, and has cognitive effects on those individuals without proper metabolic control, all of which may affect reaction times.
One of the largest implications that an increased reaction time may have is in the area of slips and falls. Falls are incurred by one third of the elderly population and are a common source of morbidity and mortality. Evidence that older subjects have an increased incidence of slips and falls when compared to healthy young adults have been attributed to increase in sway as seen by center-of-pressure or center-of-gravity (COP, COG), or head and hip variability. Diabetics have been shown to have a higher incidence of postural instability and reduced peripheral sensations, thus leading to an even higher incidence of falls resulting from slips than their healthy elder counterparts. These changes in balance metrics due to both normal aging and diabetes have been well measured, but never accurately explained. It is our contention that the postural instability may be due to slower input of information to the central nervous system, which does not allow the nervous system to react to stimuli as quickly, producing a higher incidence of slips and falls.
The aim of this study was to measure and compare reaction times to plantar (sole of the foot) touch, auditory tone, and whole body lateral movement in subjects over 50 years old with and without diabetes, as well as a group of healthy younger adults under 25 years of age. Subjects with diabetes were expected to have reaction times longer than those of the age-matched controls, while the aged controls were in turn expected to have reaction times greater than those seen in the younger adult group. The implications of the changes in reaction time will be discussed with respect to the central and peripheral nervous system.

Methods

Subjects
Subjects included 37 mature adults over 50 yrs old. Thirteen had a clinical diagnosis of type II diabetes made by their primary physician (group PN, mean = 60.6 ± 6.5 yrs, 7 Female/ 6 Male) and 23 did not (group NI, mean = 59.4 ± 8.0 yrs, 11 Female / 12 Make). Reaction times from these groups were compared to a younger adult group (age <25, N = 9, mean = 22.9 yrs, 4 Female/ 5 Male).
Screening
Subjects recruited for this study were relatively healthy individuals with no current or past history of severe heart, circulation, or breathing problems; chronic lower back pain or spasms; deformities of the spine, bones or joints (including advanced arthritis); cerebral stroke, spinal cord injuries or other damage to the nervous system; non-healing skin ulcers; advanced diabetes; current drug or alcohol dependence; or repeated falls.
Diabetic individuals targeted for this study were those with very early and mild Type II Diabetes. The subject's primary care physician undertook the diagnosis of diabetes. Targeted recruits had all been diagnosed within the last 10 years. All subjects with diabetes were using either diet or oral medication to manage blood sugar levels.
Plantar sensory tactile thresholds were measured on each sole for all subjects using Semmes-Weinstein Monofilaments. Tactile force perception thresholds on the glabrous skin of the feet were determined for the right and left feet using these monofilaments.
A certified audiologist carried out air conduction auditory threshold testing on all mature subjects (but none of the younger adults due to their health). Both mature adult groups underwent testing at 1, 2, 4, and 8 kHz in both ears. Average threshold level was recorded in decibels.
Reaction Time Protocol
Reaction time was defined as the time between a stimulus onset and a signaled response of the subject. Three different stimuli were presented – touch, tone and platform movement.

Results

Tactile Thresholds from Semmes-Weinstein Monofilament Tests
The study examined the average force necessary for detection of each group tested at each location on the foot sole. None of the diabetics in this study had significant plantar sensory loss. No significant differences were found in thresholds between right and left legs for the metatarsal and toe in any group. Data from the right and left legs were then pooled. For both plantar locations, young adults had significantly lower thresholds than the other groups. The diabetic and healthy adult groups did not differ significantly.
Audiology Thresholds
Significant differences were found both between groups and among frequencies. Diabetics had significantly higher thresholds at 8 kHz (median = 35.0 dB) and the healthy adult group had significantly higher thresholds at 4 and 8 kHz (median = 25.0 dB and 35.0 dB respectively). Additionally, there was no significant difference between the diabetics and non-diabetics at 4 and 8 kHz, but there was a significant difference at 1 kHz, and trend toward significance at 2 kHz.
Reaction Time Measurement
Reaction times to platform movement, plantar touch, and a bell tone were measured in all subjects. Measurements for reaction times were taken as the time between the beginning of the stimulus and the button press indicating subjects detected the stimuli. Averages were taken from all trials that were detected.
For platform movements, reaction times of all groups are significantly different from each other, with reaction times in the adults with diabetes being longest (mean = 777.8 ms), followed by aged matched adults (mean = 623.9 ms). Young adults had the shortest reaction times (mean = 431.0 ms) to movements.
For the touch modality, reaction times for adults with diabetes are significantly longer than both other groups (mean = 353.1 ms). However, reaction times to foot sole touch between young (mean = 216.0 ms) and healthy mature adults (mean = 331.5 ms) were not significantly different.
For the tone modality, no significant differences in reaction times were found between groups (diabetic mean = 282.6 ms; healthy adult mean = 276.9 ms; younger adult mean = 218.0 ms). For all groups, movement reaction times were significantly longer than the other two modalities (plantar touch and auditory tone), which did not differ significantly.

Discussion

At this point, it is instructive to review the results and call out the various findings to build a specific hypothesis. The key results follow:
1) Subjects with controlled type II diabetes all had mild, but measurable peripheral neuropathies in at least one nerve in the lower limb, while those without diabetes over the age of 50 had no measurable evidence of neuropathy.
2) Subjects with diabetes had increased reaction times to all three test modalities. Touch and Tone reaction times were slightly, but not significantly, higher, while platform reaction time was significantly higher.
3) Older adults, whether diabetic or not, had longer reaction times to platform moves and to foot sole touch (all locations) than did younger adults, and reaction times to the bell tone did differ between groups, even though those with diabetes had higher auditory air conduction thresholds at every frequency tested (except 8 kHz) than their non-diabetic counterparts.
4) Reaction times to platform movement are 200 to 300% longer in all groups when compared to reaction times to touch and tone.

Implications

Individuals with diabetes often have neurological side effects that affect the peripheral nervous system. However, the increase in whole body movement reaction time seen in adults with diabetes in this study can not solely be related to peripheral nervous system changes due to diabetes. Even when motor nerve conductions slow from 50.0 m/s to 40.0 m/s (as seen in nerve conduction testing here), signal transmission time for a 1 m long nerve increases only 5 ms, which does not account for a 200 ms increase in movement reaction time. An additional slowing has to be occurring in the processing of the signals by the central nervous system.
Deficits in the central nervous system (CNS) of those with diabetes may also be seen in cognitive deficits. Dey, et al. found no correlation between the duration of diabetes and cognitive function in those with non-insulin-dependent diabetes less than 18 years old. They hypothesized that in order to see the decline in cognitive function and other central nervous system effects seen by other researchers, a longer duration of disease state must be present. However, in our study, diabetics (all with less than 10 years disease duration) had a significantly higher reaction time to movement, which could be interpreted to indicate that not only are central effects present, but they manifest themselves early in the disease. These increases in movement reaction times among the mature adults with diabetes may also have an effect on posture and gait. The longer reaction times of a slipping diabetic subject will thus increase the probability of a fall. Diabetics have been shown to have a higher incidence of postural instability, longer reaction times, and reduced peripheral sensations thus leading to a higher incidence of falls resulting from slips.
Reaction times to plantar surface touch indicate the extent of peripheral neuropathy in the population of diabetics. The fact that the mature adults with diabetes had increased reaction times to plantar touch is another indication that peripheral neuropathy was present in these subjects.
Auditory reaction times measured here for diabetics and age-matched controls do roughly concur with the one reaction time study that includes diabetics. Although no significant differences in auditory reaction times were seen between mature adults with and without diabetes and their young adult counterparts, a sensorineural hearing loss was seen in the mature adults with diabetes at the mid- and high-frequencies.

Conclusion

From this study we can conclude that diabetes does affect reaction times, although the type and severity of the slowing may be related to the difficulty of the task and the prevalence of central and peripheral nerve deficits seen as side effects of diabetes. Auditory reaction times, the simplest of the tasks here with the shortest path between peripheral and central nervous system, did not show any differences in reaction times. When using a test that has a significantly longer path in the peripheral nervous system, such as the reaction time to plantar touch, slightly longer reaction times are seen in the adults with diabetes. When a more complicated task including detecting movement, signal transmission and interpretation, and response was required from the body, as in the platform movement reaction time test, a significant difference in reaction times were seen among all groups. This test takes more fully into account the peripheral nervous system signaling as well as the central nervous system processing and thus is a better overall test to determine deficits in healthy aging and aging individuals with diabetes.
We have presented here, in addition to normal auditory and touch reaction times, lateral whole body reaction time, which has been shown to be the most sensitive indicator of differences between healthy young, healthy mature adults, and mature adults with mild diabetes among the modalities tested here. In other studies, we have found that adults with diabetes have substantially higher thresholds than healthy adults to detecting whole body motion. This, in addition to the increased whole body reaction times, indicate that mild diabetes has profound effects on one’s ability to detect and react to motion, which leads to insights on their ability to detect and prevent slips and falls.

This article is based on the research article entitled, “A comparative study of reaction times between type II diabetics and non-diabetics” by Samantha J Richerson, Charles J Robinson and Judy Shum. The article on this Life Alert website and the article it is based on are covered by a Creative Commons License (version 2.0). SUMMARY OF THE CREATIVE COMMONS ATTRIBUTION LICENSE for this work: Attribution 2.0: You are free to copy, distribute, display, and perform the work; to make derivative works; to make commercial use of the work. Under the following conditions: (1) Attribution -- You must attribute the work in the manner specified by the author or licensor. For any reuse or distribution, you must make clear to others the license terms of this work. Any of these conditions can be waived if you get permission from the copyright holder. Your fair use and other rights are in no way affected by the above. Please go to the Creative Commons License site to view more information about the Creative Commons license that applies to this work.
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