Postprandial Glucose Dynamics and Associated Symptoms in Type 2 Diabetes Mellitus
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KovatchevJARFall03 12/29/03 2:40 PM Page 449
Postprandial Glucose Dynamics and
Associated Symptoms in Type 2
Diabetes Mellitus
Boris Kovatchev, PhD*
Daniel J. Cox, PhD*
Kent H. Summers, PhD†
Linda Gonder-Frederick, PhD*
William L. Clarke, MD*
*University of Virginia Health System, Charlottesville, Va
†
Eli Lilly & Company, Indianapolis, Ind
This research was supported by Eli Lilly & Company, Indianapolis, Ind.
KEY WO R D S : postprandial glucose, limit the magnitude of post-meal BG fluc-
hyperglycemia, type 2 diabetes mellitus tuation may reduce its symptomatic and
cognitive consequences.
INTRODUCTION
ABSTRACT In nondiabetic individuals postprandial glu-
Objectives: This study examined the cose (PPG) fluctuations are limited in both
dynamics of postprandial glucose (PPG) their peak value [rarely exceeding 7.8
and symptoms among adults with type 2 mmol/L (140 mg/dL)] and in their dura-
diabetes mellitus (T2DM) in their natural tion, with a peak PPG approximately 1
environment. Using a hand-held computer hour after the start of a meal, returning to
for 70 trials, 36 adults with T2DM rated preprandial levels within 2-3 hours. 1 In
symptoms, performed tests, and measured individuals with type 1 diabetes (T1DM) or
their blood glucose (BG). type 2 diabetes mellitus (T2DM) a number
of factors, such as inadequate available
Results: The mean peak PPG value was
insulin, delayed insulin action, or abnor-
11.3 mmol/L achieved 2-3 hours after meal,
malities in glucagon secretion, contribute
while highest symptom ratings and cogni-
to delayed peak PPG, and higher and pro-
tive slowing were observed within the first
longed PPG elevation.1 The American
hour after meal, at a time corresponding to
Diabetes Association Consensus Statement
the steepest slope of PPG increase. Thus,
on postprandial hyperglycemia concluded
we hypothesized that postprandial symp-
that “in general, a measurement of plasma
toms maybe related to a higher rate of BG
glucose 2 h after the start of a meal is prac-
increase, which was confirmed by high cor-
tical, generally approximates the peak value
relations (r = 0.5-0.75) between symptom
in patients with diabetes, and provides a
ratings and BG rate of increase.
reasonable assessment of postprandial
Conclusions: We conclude that postprandi- hyperglycemia.” 1
al symptom elevation is related to the rate
However, the dynamics of PPG are
of BG increase, thus treatments designed to
complex, dependent on many factors, such
The Journal of Applied Research • Vol. 3, No. 4, Fall 2003 449KovatchevJARFall03 12/29/03 2:40 PM Page 450
as the amount and the composition of the physiological as well as epidemiologic stud-
meal, and still not well understood. Even ies that excessive post-load glucose excur-
though a linear relationship between post- sions have acute and chronic harmful
prandial and post-challenge (after a 75-g effects on the endothelium and vessel
oral glucose load) glucose 2 hours after a wall.”3 Thus, an assessment of PPG dynam-
meal was established in laboratory condi- ics in the natural environment would be a
tions,2 the dynamics of this relationship in valuable tool for evaluation of glycemic
the field is difficult to assess.3 Perhaps as a control.
result of the lack of a standard PPG assess- In addition to the long-term negative
ment, the usual clinical appraisal of effects of elevated PPG, clinical experience
glycemic control includes only better- suggests a relationship between postprandi-
defined and more stable measures, such as al hyperglycemia and acute and transient
fasting plasma glucose (FPG) and/or glyco- increases in psychological symptoms and
sylated hemoglobin (HbA1c). However, cognitive disruptions.2,16-18 However, there
FPG reflects blood glucose (BG) values have been no prospective and objective
after the effect of carbohydrate intake has investigations of the relationship of such
been eliminated and HbA1c represents the symptoms/cognitive dysfunctions with post-
average BG over a certain period of time, prandial BG parameters, especially with
which makes both of these measures insen- parameters of postprandial BG dynamics in
sitive to BG excursions throughout the the natural environment of people with dia-
day—in particular to PPG fluctuations. For betes. For example, it is unclear whether
example, a recent study4 of more than 800 the peak absolute value of PPG is responsi-
people with T2DM found that after meals, ble for triggering symptoms, or symptoms
many subjects had glucose levels >8.9 are mainly related to the speed and magni-
mmol/L (160 mg/dL) and/or glucose excur- tude of BG increase post-meal. This study
sions >2.2 mmol/L (40 mg/dL) despite investigates when BG peaks in T2DM
HbA1cKovatchevJARFall03 12/29/03 2:40 PM Page 451
Procedure (Lifescan, Milpitas, Calif.). Three precau-
Subjects completed a series of psychomet- tions were taken to encourage and monitor
ric instruments, including the Beck whether symptom entries and cognitive test-
Depression Inventory. They were then ing preceded SMBG. (1) Each HHC trial
instructed to use the Handspring Visor began with the message, “No blood sample
Platinum, (Handspring, Inc, Mountain yet.” (2) The HHC tracked the elapsed time
View, CA) hand-held computer (HHC) between the prompt “Measure your BG”
immediately before self-monitoring of and the entry of this SMBG reading. Since
blood glucose (SMBG). No specific SMBG at least 10 seconds are required for a sub-
schedule was given to the subjects; they ject to lance a finger, collect a blood sam-
were required only to complete 70 HHC tri- ple, and analyze BG level with the One
als within 3-4 weeks. The HHC was Touch Ultra, any readings entered in less
equipped with our custom-developed symp- than 10 seconds were considered invalid.
tom/behavioral assessment software. At (3) The BG readings entered by the subjects
each trial the HHC first collected data on into the HHC were compared to data in the
perceived symptoms and cognitive perform- glucometer’s memory to ensure accuracy of
ance. Then, subjects measured and entered SMBG results. An earlier version of this
their BG level. HHC routine developed for Psion 250 HHC
Symptoms. At each trial the HHC presented was used in our previous studies of symp-
in a random order 16 symptoms and toms and behaviors related to hypo-
prompted subjects to rate them on a scale glycemia.19-21
from 0 = none to 6 = extreme. There were 6 Data Analysis
physical symptoms (need to urinate; BG values were averaged across all subjects
sweet/funny taste; dry eyes, nose, mouth; in 10 time intervals post-meal and plotted
tired/fatigued; thirsty; nausea), 6 mood and compared using univariate ANOVA. To
symptoms (nervous/anxious; irritable/frus- obtain comparable estimates of average BG
trated; restless/jittery; sad/blue; across these intervals, each time interval
giddy/funny; don’t care/apathetic), and 4 was at least one half-hour in duration and
cognitive symptoms (difficulty concentrat- was required to contain at least 200 SMBG
ing; difficulty speaking; uncoordinated; readings, that is, at least 8% of all
slowed thinking). HHC/SMBG readings. This approach
Cognitive tests. The HHC presented the fol- resulted in approximately equal weights (in
lowing tests: (1) 10 mental subtraction prob- terms of number of readings) of the time
lems that used randomly generated 3-digit intervals.
numbers, with subjects entering answers on Symptoms and cognitive test performance.
a number pad; and (2) 2 levels of the Paced In order to eliminate the influence of hypo-
Serial Addition Test (PSAT) presenting a glycemia, symptom ratings and test results
sequence of single-digit numbers for which were considered only if BG was greater
the subject has to enter the sum of each pair than 6.7 mmol/L (120 mg/dL). In order to
of sequential numbers. Levels 1 and 2 of evaluate the magnitude of each individual
the test present numbers at 4-second and 2- postprandial symptom its ratings were aver-
second intervals, respectively. aged across subjects at 1-hour time inter-
Other parameters. The HHC asked subjects vals post-meal and compared using
to enter the time when “you began eating univariate ANOVA. The average symptom
your last meal” and at the end of each trial, magnitude in each category, (physical,
the subjects were prompted to measure and mood, and cognitive) was computed as well.
enter their BG. For the latter all subjects Similarly, cognitive impairment was
used One Touch Ultra glucometers assessed using the time to complete 10
The Journal of Applied Research • Vol. 3, No. 4, Fall 2003 451KovatchevJARFall03 12/29/03 2:40 PM Page 452
Figure 1. Postprandial blood glucose (BG) levels and postprandial increase in overall symptom
reporting are plotted against elapsed time after a meal (x-axis in minutes). The postprandial BG
values (black squares) are presented in the primary y-axis and demonstrate a peak PPG value
at approximately 2.5 – 3 hours after a meal. The number of elevated postprandial symptoms
(symptoms with ratings greater than 0 over the course of PPG) is presented in the secondary y-
axis (black triangles) and demonstrates a peak symptom reporting within 1 hour after a meal.
mental subtractions and the number of cor- ject’s BG rate of increase (BGRI). This
rect additions on the faster (Level 1) and variable is similar to the previously reported
slower (Level 2) PSAT, averaged at 1-hour BG rate of change,22 but takes into account
intervals post-meal. Average postprandial only increases in BG, not overall fluctua-
BG 1, 2, and 3 hours after meal was corre- tions. Specifically, BGRI was computed as
lated with corresponding symptom ratings the average of the ratios (BG(t2)-BG(t1))/(t2-
and cognitive performance results. In order t1), where BG(t2) > BG(t1) were any two
to account for multiple tests we used increasing consecutive SMBG readings of a
Bonferroni corrections, accepting only subject taken at times t2 and t1 within the
results significant at P 6.7 mmol/L. days). However, since fast BG increases are
Rate of BG increase. From each subject’s predominantly observed after meals, we
SMBG data collected concurrently with the assumed that BGRI was mostly influenced
HHC, we computed an estimate of this sub- by postprandial BG elevation.
452 Vol. 3, No. 4, Fall 2003 • The Journal of Applied ResearchKovatchevJARFall03 12/29/03 2:40 PM Page 453
Table 1. Average Postprandial Symptom Ratings* and Cognitive Test Performance.
Pre-prandial Postprandial Ratings F (P)
1h 2h 3h
Need to urinate 1.0 1.7 1.3 1.2 7.7 (KovatchevJARFall03 12/29/03 2:40 PM Page 454
Table 2. Correlations of Average Symptom Ratings* and Cognitive Test Performance with
Blood Glucose Rate of Increase.
Correlation Coefficients**
1h 2h 3h
Need to urinate 0.48 -0.02 0.02
Sweet/funny taste 0.39 0.01 0.08
Dry eyes, nose, mouth 0.46 -0.05 -0.02
Tired/fatigued 0.41 0.21 0.18
Thirsty 0.33 0.08 0.03
Nausea 0.42 0.02 0.12
Average magnitude of physical
symptoms 0.52 0.06 0.09
Nervous/anxious 0.69 0.48 0.43
Irritable/frustrated 0.56 0.28 0.33
Restless/jittery 0.50 0.52 0.45
Sad/blue 0.68 0.53 0.44
Giddy/funny 0.50 0.07 -0.06
Not care/apathetic 0.66 0.54 0.37
Average magnitude of mood
symptoms 0.70 0.49 0.44
Difficulty concentrating 0.60 0.39 0.30
Difficulty speaking 0.75 0.34 .25
Uncoordinated 0.76 0.52 .22
Slowed thinking 0.58 0.34 .31
Average magnitude of cognitive
symptoms 0.74 0.44 0.30
Time to complete 10 mental
subtractions (sec.) 0.27 0.06 0.02
PSAT – Level 1
Number correct answers -0.21 -0.21 0.18
PSAT – Level 2
Number correct answers -0.26 -0.02 0.15
* Using a scale from 0 = none to 6 = extreme.
** With this sample size correlations above 0.37 yield P-levels below P= 0.05, while correlations above
0.47 are significant at P = 0.01. The latter are indicated in bold.
Postprandial Symptoms and Cognitive (Table 1).
Slowing Specifically, 5 of the 6 physical symp-
Most physical, mood, and cognitive symp- toms were rated higher post-meal: subjects
toms displayed similar patterns of highest reported a greater need to urinate (F = 7.7,
average rating within the first hour after PKovatchevJARFall03 12/29/03 2:40 PM Page 455
thirst (F = 11.2, PKovatchevJARFall03 12/29/03 2:40 PM Page 456
tions with BGRI were highest within 1 hour design of the study was that the BG rate of
post-meal, and gradually decreased at 2 and increase could not be computed strictly for
3 hours post-meal. Since PPG increase pre-to-postprandial periods, that is, the
slowed down at 2 and 3 hours post-meal, slope of PPG increase could not be estimat-
and the PPG curve gradually flattened, this ed directly. This was due to the lack of suf-
was precisely the effect to be expected if ficient number of BG readings within a
symptoms were related to PPG increase and pre- and corresponding postprandial peri-
not to extreme PPG values. With this sam- od; at least two, pre-and postprandial, read-
ple size (N = 36) correlations above 0.47 ings on several days per subject are needed
yielded P-levels below 0.01 and were con- in order to estimate PPG slope.
sidered significant. Several correlation Instead, we confirmed a less specific
coefficients were above 0.6. For example, hypothesis: higher postprandial symptoms
the average magnitude of “difficulty speak- are related to higher overall BG rate of
ing” and “uncoordinated” 1 hour post-meal increase. The BGRI was based on a previ-
produced a correlation coefficient of 0.75- ously reported measure, BG rate of
0.76 with BGRI (see Table 2). change,22 but it took into account only con-
secutively increasing SMBG readings, not
DISCUSSION any two consecutive readings. As computed
This study used new monitoring tech- here, BGRI was not specific to postprandial
nology (HHC and custom software) to time periods; however, we assumed that it
assess in-the-field dynamics of postprandial was most influenced by the largest (per
BG and associated symptoms and cognitive hour) BG increases that subjects experi-
impairment in adults with type 2 diabetes enced post-meal. Indeed, it was illogical to
mellitus. Our data allowed for a reconstruc- expect that large and fast BG elevations
tion of PPG dynamics in our subjects’ natu- could have occurred with no relationship to
ral environment and confirmed laboratory a preceding significant carbohydrate intake.
observations and common knowledge that Thus, we could speculate that the process of
PPG is most elevated 2-3 hours after meal. 1 PPG elevation contributed to symptoms
In addition, we demonstrated that after more than the absolute values of postpran-
meals self-reported physical symptoms and dial hyperglycemia. While this speculation
moods became significantly elevated, and may be confirmed (or rejected) by future
that objectively determined cognitive slow- studies, here we were able to clearly
ing of approximately 30% was apparent. observe two related properties: (1) symp-
Surprisingly, however, symptom eleva- tom ratings were higher during the first
tion and cognitive slowing did not follow hour post-meal and this was the period of
the course of absolute PPG values. Instead, steepest slope of PPG increase, and (2)
for most symptoms highest symptom rat- postprandial symptoms were highly corre-
ings were observed within 1 hour after a lated with subject’s overall rate of BG
meal (Table 1), not when PPG was at its increase.
peak 2-3 hours post-meal. Overall, plotting In fact, the correlations between mood
a summary of all symptoms and PPG and cognitive symptoms and BGRI were
against the time elapsed after a meal very high, in some cases higher than 0.7
revealed that symptoms generally occurred (Table 2). Given that symptom ratings were
during the time of steepest slope of PPG derived from behavioral self-assessment,
increase (Figure 1). Thus, we hypothesized while BGRI was derived from concurrent
that postprandial symptoms occurred during but quite different sets of SMBG data
times when BG increase was fastest. With downloaded from the subjects’ glucometer
our data, however, we could not definitely memories, correlations of that magnitude
confirm this notion. One limitation in the imply very strong [linear] relationships.
456 Vol. 3, No. 4, Fall 2003 • The Journal of Applied ResearchKovatchevJARFall03 12/29/03 2:40 PM Page 457
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