Seasonal variation in HbA1c in patients with Type 2 diabetes mellitus

Seasonal variation of HbA1c levels in diabetic and non-diabetic patients

Background

Hemoglobin A1c (HbA1c) serves as a pivotal marker for long-term glycemic control. The Diabetes Control and Complications Trial (DCCT) established its relevance, yet gaps exist in understanding potential seasonal variations in HbA1c levels among diabetic patients. The study highlights the need to explore potential seasonal variations in HbA1c levels and their impact on diabetic patients.

Materials and methods

This is an observational study conducted in a tertiary care hospital from January to December 2019, the study analyzed HbA1c levels in 8138 patients. Blood samples were collected using Potassium EDTA-containing vials and processed with an automated analyzer. Seasonal variations were explored using time series analysis.

Results

Mean HbA1c levels peaked during the monsoon (June to September) and were lowest in autumn (October to November). Subgroup analysis revealed differences in patients with HbA1c values below and above 6.5 %. Those with controlled blood sugar showed higher levels in winter (December to February) and monsoon (June to September), while patients with HbA1c values ≥ 6.5 % exhibited significantly lower levels in monsoon (June to September) and autumn (October to November) compared to summer (March to May).

Conclusion

In contrast to global trends, Indian patients demonstrated distinct seasonal variations in HbA1c levels. The highest levels during the monsoon (June to September) may be linked to reduced outdoor activity and dietary changes. The study emphasizes the need for tailored diabetes management considering seasonal influences. Further extensive, longitudinal studies across diverse Indian regions are recommended to comprehensively grasp the impact of seasonal changes on diabetes outcomes.

Temperature variability and common diseases of the elderly in China: a national cross-sectional study

BACKGROUND

In the context of climate change, it has been well observed that short-term temperature variability (TV) could increase the overall and cause-specific mortality and morbidity. However, the association between long-term TV and a broader spectrum of diseases is not yet well understood, especially in the elderly.

METHODS

Our study used data from the fourth Urban and Rural Elderly Population (UREP) study. Long-term TV was calculated from the standard deviation (SD) of daily minimum and maximum temperatures within the study periods (2010-2014, 2011-2014, 2012-2014, 2013-2014, and 2014). Ten self-reported diseases and conditions were collected by questionnaire, including cataract, hypertension, diabetes, cardio-cerebrovascular diseases, stomach diseases, arthritis, chronic lung disease, asthma, cancer, and reproductive diseases. The province-stratified logistic regression model was used to quantify the association between long-term TV and the prevalence of each disease.

RESULTS

A total of 184,047 participants were included in our study. In general, there were significant associations between TV and the prevalence of most diseases at the national level. Cardio-cerebrovascular disease (OR: 1.16, 95% CI: 1.13, 1.20) generated the highest estimates, followed by stomach diseases (OR: 1.15, 95% CI: 1.10, 1.19), asthma (OR: 1.14, 95% CI: 1.06, 1.22), chronic lung diseases (OR: 1.08, 95% CI: 1.03, 1.13), arthritis (OR: 1.08, 95% CI: 1.05, 1.11), and cataract (OR: 1.06, 95% CI: 1.02, 1.10). Moreover, the associations varied by geographical regions and across subgroups stratified by sex, household income, physical activity, and education.

CONCLUSIONS

Our study showed that long-term exposure to TV was associated with the prevalence of main diseases in the elderly. More attention should be paid to the elderly and targeted strategies should be implemented, such as an early warning system.

Seasonal variations and the influence of COVID-19 pandemic on hemoglobin A1c, glycoalbumin, and low-density lipoprotein cholesterol

Aim

The purpose of the study was to investigate seasonal variations in HbA1c, GA and LDL-C and to examine the effects of the COVID-19 pandemic on these variations and on glycemic and lipid control themselves in patients with type 2 diabetes.

Patients and methods

The subjects were outpatients with type 2 diabetes who had received standard treatment for glycemic control for more than 3 years. Data for patients who visited our hospital from January 2021 to March 2021 were retrospectively investigated based on electronic medical records.

Results

HbA1c showed seasonal variation (high in winter–spring and low in summer–autumn), and this was similar during the COVID-19 pandemic. However, the mean HbA1c over 1 year was significantly elevated during the COVID-19 pandemic (7.53 ± 1.02% in 2020) compared with the previous 2 years: (7.34 ± 0.91 in 2018, 7.39 ± 0.93 in 2019; 2020 vs. 2018; 0.19%, P < 0.001; 2020 vs. 2019; 0.14%, P = 0.0013) and the difference was larger in winter. GA showed no apparent seasonal variation, but mean GA during the COVID-19 pandemic was elevated compared with earlier years (2020 vs. 2018, P < 0.001; 2020 vs. 2019, P < 0.001). LDL-C did not show apparent seasonal variation and was unaffected by COVID-19 pandemic.

Conclusion

The COVID-19 pandemic influenced mean HbA1c and GA levels over 1 year, but did not affect seasonal variations, while LDL-C was not affected by COVID-19. Observation of these levels over a longer period is warranted to determine the longer-term influence of the COVID-19 pandemic.

Association between Physical Activity and Seasonal Variations in Metabolic and Vascular Function in Adults

This article highlights the association between physical activity (PA) and seasonal variations in metabolic and vascular function in adults. Increasing PA is an important method for preventing cardiovascular disease (CVD) and all-cause mortality by improving blood glucose, blood pressure, blood lipid profiles, body fat, insulin resistance, and vascular function, such as endothelial function. Conversely, various factors, such as seasonal climate conditions, may affect the amount of PA that individuals undertake. Changes in PA often induce seasonal variations in metabolic and vascular function; the deterioration of such functions in winter is the most prominent, and there is clear evidence of an increased risk of CVD in this season. Understanding the influence of PA on seasonal variations observed in metabolic and vascular function is necessary for the management of these physiological functions. In this article summary, few studies have proven that maintaining PA can suppress the variations, and it remains unclear what types, intensities, and durations of regular PA are effective for circumventing seasonal impact. In addition to further studies, there is a need to educate individuals about the strategies to manage PA and other aspects of their lifestyles throughout the year, particularly in winter.

Climatic drivers of melioidosis in Laos and Cambodia: a 16-year case series analysis

BACKGROUND

Burkholderia pseudomallei is the cause of melioidosis, a serious and difficult to treat infection that is endemic throughout the tropics. Melioidosis incidence is highly seasonal. We aimed to identify the climatic drivers of infection and to shed light on modes of transmission and potential preventive strategies.

METHODS

We examined the records of patients diagnosed with melioidosis at the Microbiology Laboratory of Mahosot Hospital in Vientiane, Laos, between October, 1999, and August, 2015, and all patients with culture-confirmed melioidosis presenting to the Angkor Hospital for Children in Siem Reap, Cambodia, between February, 2009, and December, 2013. We also examined local temperature, humidity, precipitation, visibility, and wind data for the corresponding time periods. We estimated the B pseudomallei incubation period by examining profile likelihoods for hypothetical exposure-to-presentation delays.

FINDINGS

870 patients were diagnosed with melioidosis in Laos and 173 patients were diagnosed with melioidosis in Cambodia during the study periods. Melioidosis cases were significantly associated with humidity (p<0·0001), low visibility (p<0·0001), and maximum wind speeds (p<0·0001) in Laos, and humidity (p=0·010), rainy days (p=0·015), and maximum wind speed (p=0·0070) in Cambodia. Compared with adults, children were at significantly higher odds of infection during highly humid months (odds ratio 2·79, 95% CI 1·83-4·26). Lung and disseminated infections were more common during windy months. The maximum likelihood estimate of the incubation period was 1 week (95% CI 0-2).

INTERPRETATION

The results of this study demonstrate a significant seasonal burden of melioidosis among adults and children in Laos and Cambodia. Our findings highlight the risks of infection during highly humid and windy conditions, and suggest a need for increased awareness among at-risk individuals, such as children.

FUNDING

Wellcome Trust.

Season and vitamin D status are independently associated with glucose homeostasis in pregnancy

BACKGROUND

Vitamin D status and season are intrinsically linked, and both have been proposed to be associated with glucose homeostasis in pregnancy, with conflicting results. We aimed to determine if exposure to winter and low maternal 25 hydroxyvitamin D (25OHD) in early pregnancy were associated with maternal glucose metabolism.

METHODS

This is a secondary data analysis of 334 pregnant women enrolled in the ROLO study, Dublin. Serum 25OHD, fasting glucose, insulin and insulin resistance (HOMA-IR) were measured in early (12 weeks' gestation) and late pregnancy (28 weeks' gestation). Season of first antenatal visit was categorised as extended winter (November-April) or extended summer (May-October). Multiple linear regression models, adjusted for confounders, were used for analysis.

RESULTS

Those who attended their first antenatal visit in extended winter had lower 25OHD compared to extended summer (32.9 nmol/L vs. 44.1 nmol/L, P < 0.001). Compared to those who attended their first antenatal visit during extended summer, extended winter was associated with increased HOMA-IR in early-pregnancy (46.7%) and late pregnancy (53.7%), independent of 25OHD <30 nmol/L and confounders. Early pregnancy 25OHD <30 nmol/L and extended winter were independently associated with significantly higher fasting glucose in late pregnancy (B = 0.15 and 0.13, respectively).

CONCLUSIONS

Women who attended their first antenatal visit during the months of extended winter were more likely to have raised insulin resistance in early pregnancy, which had a lasting association to 28 weeks, and was independent of 25OHD. Our novel findings imply that seasonal variation in insulin resistance may not be fully explained by differences in vitamin D status. This could reflect circannual rhythm or seasonal lifestyle behaviours, and requires further exploration.

TRIAL REGISTRATION

ISRCTN registry, ISRCTN54392969, date of registration: 22/04/2009, retrospectively registered.

The impact of ambient temperature on HbA1c in Taiwanese type 2 diabetic patients: The most vulnerable subgroup

BACKGROUND/PURPOSE

The relationship between temperature variability and HbA1c has been reported in Caucasians, but not for Asians of Taiwanese origin. This study investigated the impact of temperature on HbA1c in various groups of Taiwanese with type 2 diabetes in Taiwan.

METHODS

For this longitudinal follow-up study which started in 2006, we recruited a total of 4399 patients with type 2 diabetes who had been regularly followed up at Chi Mei Medical Center and obtained local temperature data for 2006 to 2011 from Taiwan's Central Weather Bureau. We used a generalized estimated equation (GEE) to analyze the HbA1c level and its change over time with temperature and temperature changes, respectively.

RESULTS

We found a negative correlation between HbA1c and temperature (R = -0.475, p = 0.001). For every 1°C decrement in temperature, there was an increase in the risk of having a HbA1c level >7% [p < 0.001, adjusted odds ratio (OR): 1.01]. There was a significantly higher risk of HbA1c > 7% among those in the lowest quartile of temperatures than the highest quartile (p = 0.0038, adjusted OR: 1.13). Patients with diabetic patients were at higher risk of HbA1C > 7% in the winter and spring than those in the summer (adjusted OR: 1.13, p = 0.0027; adjusted OR: 1.14, p = 0.0022). After adjusting for various confounders, we found people who were younger than 65 years old, people who had diabetes for longer than 6 years, and people who had a body mass index (BMI) < 24 to be more susceptible to temperature changes (p = 0.0022, β: 0.0095; p < 0.0001, β: 0.0125; p < 0.0001, β: 0.016, respectively).

CONCLUSION

Our study suggests cold weather may adversely affect HbA1c levels in Taiwanese people with type 2 diabetes, especially in people under 65 years old, people with diabetes for longer than 6 years, and those with a BMI < 24.

Seasonal variations in glycemic control of type 2 diabetes in Korean women

BACKGROUND AND AIMS

Seasonal variations in lifestyle, such as food intake and physical activity, have been reported. Glycemic control in type 2 diabetes mellitus (T2DM) may be affected by such changes. We investigated seasonal variations in glycemic control, food intake, and physical activity in type 2 diabetic patients.

METHODS

This prospective observational study included 37 Korean female patients who had <8.0 % hemoglobin A1c (HbA1c) and managed diabetes by oral anti-diabetic drugs or lifestyle modification only. Participants underwent four or five assessments, including total physical activity (household, leisure-time, and occupational activity) (metabolic equivalent of test-h/day), food intake (kcal/day), HbA1c, and anthropometry every 3 months (August, November, February, May, and August in the Northern Hemisphere) over 1 year. When anti-diabetic drugs were changed, we analyzed the data just before the changes.

RESULTS

The mean HbA1c levels (%) of August and November in 2008, and February, May, and August in 2009 were 7.0 ± 0.1, 6.9 ± 0.1, 7.2 ± 0.2, 7.4 ± 0.2, and 7.2 ± 0.2, respectively (P = 0.018). The change of HbA1c was nearly 0.5 % for the 1-year period. From August to May of the following year, there were also seasonal variations in food intake (1,872 ± 143, 1,739 ± 97, 1,673 ± 86, 1,561 ± 132, respectively; P = 0.013), and total physical activity [7.7 (3.7-14.6), 6.3 (2.8-10.4), 5.1 (2.7-12.6), and 11.2 (4.7-20.5), respectively; P = 0.048]. However, the seasonal variations of HbA1c and total physical activity became non-significant when farmers were excluded.

CONCLUSIONS

These data suggested that glycemic control, total physical activity, and food intake varied seasonally in Korean T2DM patients. These seasonal variations should be considered in education for glycemic control.

HbA1c for screening and diagnosis of diabetes mellitus

HbA1c has become the gold standard for monitoring glycemic control in patients with diabetes mellitus. The use of this test has been expanded to diagnose and screen for diabetes mellitus with the endorsement of influential diabetes societies and the World Health Organization. The literature on the use of HbA1c for the diagnosis and screening of diabetes mellitus was critically examined. There is substantial recent literature on this topic with strong advocates for the use of HbA1c to diagnose and screen for diabetes and equally strong detractors for its use. Advocates of the use of HbA1c cite challenges in respect of patient compliance and the analysis of glucose and inconsistency of diagnosis with glucose-based diabetes diagnosis with the elimination or reduction in these challenges in HbA1c-based diagnosis. Detractors of its use cite increased cost, concerns about the availability of HbA1c testing, and the influence of demographic and clinical factors on HbA1c results that make the use of a single-threshold values questionable for different ethnic and age groups. Despite the recommendation of many international diabetes societies that HbA1c be used for screening and diagnosis of diabetes mellitus, there is a wide divergence of opinion on this use.

Seasonal variations of insulin sensitivity from a euglycemic insulin clamp in elderly men

INTRODUCTION

Seasonal variations in hemoglobin-A1c have been reported in diabetic patients, but the underlying mechanisms have not been elucidated.

AIMS

To study if insulin sensitivity, insulin secretion, and fasting plasma glucose showed seasonal variations in a Swedish population-based cohort of elderly men.

METHODS

Altogether 1117 men were investigated with a euglycemic insulin clamp and measurements of fasting plasma glucose and insulin secretion after an oral glucose tolerance test. Values were analyzed in linear regression models with an indicator variable for winter/summer season and outdoor temperature as predictors.

RESULTS

During winter, insulin sensitivity (M/I, unit = 100 × mg × min(-1) × kg(-1)/(mU × L(-1))) was 11.0% lower (4.84 versus 5.44, P = 0.0003), incremental area under the insulin curve was 16.4% higher (1167 versus 1003 mU/L, P = 0.007). Fasting plasma glucose was, however, not statistically significantly different (5.80 versus 5.71 mmol/L, P = 0.28) compared to the summer season. There was an association between outdoor temperature and M/I (0.57 units increase (95% CI 0.29-0.82, P < 0.0001) per 10°C increase of outdoor temperature) independent of winter/summer season. Adjustment for life-style factors, type 2 diabetes, and medication did not alter these results.

CONCLUSIONS

Insulin sensitivity showed seasonal variations with lower values during the winter and higher during the summer season. Inverse compensatory variations of insulin secretion resulted in only minor variations of fasting plasma glucose. Insulin sensitivity was associated with outdoor temperature. These phenomena should be further investigated in diabetic patients.

HbA(1c) levels in schoolchildren with type 1 diabetes are seasonally variable and dependent on weather conditions

AIMS/HYPOTHESIS

We evaluated seasonal HbA(1c) changes in children with type 1 diabetes and its relation with measures of weather conditions.

METHODS

HbA(1c) changes over more than 3 years were evaluated in type 1 diabetic patients who were younger than 18 years and had diabetes duration of more than 12 months, and correlated with measures of weather conditions (ambient temperature, hours of sunshine and solar irradiance). After comparison of autocorrelation patterns, patterns of metabolic control and meteorological data were evaluated using Spearman rank correlation.

RESULTS

A total of 3,935 HbA(1c) measurements in 589 school (≥ 7 years) and 88 preschool (<7 years) children were analysed. Mean (± SD) HbA(1c) level for the whole study period was 7.65 ± 1.12%. The lowest HbA(1c) levels were observed in late summer and the highest in winter months, with differences consistently exceeding 0.44%. Autocorrelation analysis of HbA(1c) levels in schoolchildren showed a sine-wave pattern with a cycle length of roughly 12 months, which mirrored changes in ambient temperature. Strong negative correlations of HbA(1c) with ambient temperature (R = -0.56; p = 0.0002), hours of sunshine (R= -0.52; p = 0.0007) and solar irradiance (R = -0.52; p = 0.0006) were present in schoolchildren, but not in preschoolers (p ≥ 0.29 for each correlation).

CONCLUSIONS/INTERPRETATION

Seasonal changes of HbA(1c) levels in schoolchildren with type 1 diabetes are a significant phenomenon and should be considered in patient education and diabetes management. They may potentially affect the results of clinical trials using HbA(1c) levels as their primary outcome, as well as HbA(1c)-based diagnosis of diabetes.

Daily steps are low year-round and dip lower in fall/winter: findings from a longitudinal diabetes cohort

BACKGROUND

Higher walking levels lead to lower mortality in type 2 diabetes, but inclement weather may reduce walking. In this patient population, we conducted a longitudinal cohort study to objectively quantify seasonal variations both in walking and in two vascular risk factors associated with activity levels, hemoglobin A1C and blood pressure.

METHODS

Between June 2006 and July 2009, volunteer type 2 diabetes patients in Montreal, Quebec, Canada underwent two weeks of pedometer measurement up to four times over a one year follow-up period (i.e. once/season). Pedometer viewing windows were concealed (snap-on cover and tamper proof seal). A1C, blood pressure, and anthropometric parameters were also assessed. Given similarities in measures for spring/summer and fall/winter, and because not all participants completed four assessments, spring and summer values were collapsed as were fall and winter values. Mean within-individual differences (95% confidence intervals) were computed for daily steps, A1C, and systolic and diastolic blood pressure, by subtracting spring/summer values from fall/winter values.

RESULTS

Among 201 participants, 166 (82.6%) underwent at least one fall/winter and one spring/summer evaluation. Approximately half were women, the mean age was 62.4 years (SD 10.8), and the mean BMI was 30.1 kg/m2 (SD 5.7). Step counts averaged at a sedentary level in fall/winter (mean 4,901 steps/day, SD 2,464) and at a low active level in spring/summer (mean 5,659 steps/day, SD 2,611). There was a -758 (95% CI: -1,037 to -479) mean fall/winter to spring/summer within-individual difference. There were no significant differences in A1C or in anthropometric parameters. Systolic blood pressure was higher in fall/winter (mean 137 mm Hg, SD 16) than spring/summer (133 mm Hg, SD 14) with a mean difference of 4.0 mm Hg (95% CI: 2.3 to 5.7).

CONCLUSIONS

Daily step counts in type 2 diabetes patients are low, dipping lower during fall/winter. In this medication-treated cohort, A1C was stable year-round but a fall/winter systolic blood pressure increase was detected. Our findings signal a need to develop strategies to help patients increase step counts year-round and prevent both reductions in step counts and increases in blood pressure during the fall and winter.

Seasonal fluctuations of glycated hemoglobin levels in Japanese diabetic patients

AIMS

We examined whether glycated hemoglobin (HbA(1C)) levels of Japanese diabetic patients showed seasonal fluctuations.

METHODS

Subjects included 2511 diabetic patients who regularly visited a single diabetic outpatient clinic for 10 years. A total of 253,477 HbA(1C) measurements, as well as sex, age, BMI, type of diabetes, and mode of therapy were extracted from a hospital-based database. For the cross-sectional and longitudinal analyses, average monthly HbA(1C) values of subjects and amplitudes of seasonal fluctuations were calculated. For the time-series analysis, seasonal adjustment factors of each subject were classified as complete, incomplete, or no fluctuation.

RESULTS

Subjects showed a clear seasonal fluctuation of HbA(1C) levels, with highest levels in March (7.69%) and lowest levels in August (7.46%; p<0.001). The amplitudes of the seasonal fluctuations were associated with the mean HbA(1C) levels. The time-series analysis showed that 78.3% of patients had complete or incomplete seasonal fluctuations. HbA(1C) levels were highest in winter-spring and lowest in summer-autumn in most patients; however, some patients showed a reverse pattern.

CONCLUSIONS

Seasonal fluctuations of HbA(1C) levels were recognized in most of the Japanese diabetic patients. Physiological or metabolic factors related to temperature may be the main cause of seasonal fluctuations in HbA(1C) levels.

Seasonal variation in hemoglobin A1c: is it the same in both hemispheres?

INTRODUCTION

There are several reports from locations in the northern hemisphere of seasonal variation in hemoglobin A1c (HbA1c) levels with higher values noted in the cooler months. The variation has been attributed to holiday seasons, temperature differences, and changes in diet. This article describes the seasonal variation in both hemispheres and in a country on the equator with minimal temperature variation.

METHODS

The mean and median HbA1c by month was calculated for a maximum of 2 years for HbA1c data from the different locations: Edmonton and Calgary, Canada; Singapore; Melbourne, Australia; and Marshfield, Wisconsin. The mean monthly temperature for each location was found from available meteorological information.

RESULTS

In both northern and southern hemispheres, the HbA1c was higher in cooler months and lower in the warmer months. In Singapore, where there is minimal temperature variation, there is also minimal variation in HbA1c values over the year. The difference in HbA1c over a year appears to be related to the difference in temperature.

CONCLUSION

Hemoglobin A1c is higher in cooler months and lower in the warmer months in both hemispheres. In a country with minimal monthly temperature variation, there is only minimal variation in HbA1c values through the year. In all locations, the mean and median HbA1c declined over the study period, possibly due to better glycemic control of patients with diabetes or an increase in use of HbA1c as a screening test for diabetes or a combination of both.

Seasonal variation in fasting glucose and HbA1c in patients with type 2 diabetes

Seasonal variations in fasting glucose and HbA1c levels in 638 diabetic patients (attending a primary care diabetic clinic during 2003-2007) were examined and found to be significantly higher in colder than in warmer months. Moreover, there were apparent peaks in fasting glucose levels after Christmas and Easter months. This study provides further evidence of monthly fluctuations in glycemic control, underscoring the need to consider seasonal/cultural effects when managing diabetic patients.

Walking behaviour and glycemic control in type 2 diabetes: seasonal and gender differences--study design and methods

Background

The high glucose levels typically occurring among adults with type 2 diabetes contribute to blood vessel injury and complications such as blindness, kidney failure, heart disease, and stroke. Higher physical activity levels are associated with improved glycemic control, as measured by hemoglobin A1C. A 1% absolute increase in A1C is associated with an 18% increased risk for heart disease or stroke. Among Canadians with type 2 diabetes, we postulate that declines in walking associated with colder temperatures and inclement weather may contribute to annual post-winter increases in A1C levels.

Methods

During this prospective cohort study being conducted in Montreal, Quebec, Canada, 100 men and 100 women with type 2 diabetes will undergo four assessments (once per season) over a one-year period of observation. These assessments include (1) use of a pedometer with a concealed viewing window for a two-week period to measure walking (2) a study centre visit during which venous blood is sampled for A1C, anthropometrics are assessed, and questionnaires are completed for measurement of other factors that may influence walking and/or A1C (e.g. food frequency, depressive symptomology, medications). The relationship between spring-fall A1C difference and winter-summer difference in steps/day will be examined through multivariate linear regression models adjusted for possible confounding. Interpretation of findings by researchers in conjunction with potential knowledge "users" (e.g. health professionals, patient groups) will guide knowledge translation efforts.

Discussion

Although we cannot alter weather patterns to favour active lifestyles, we can design treatment strategies that take seasonal and weather-related variations into account. For example, demonstration of seasonal variation of A1C levels among Canadian men and women with T2D and greater understanding of its determinants could lead to (1) targeting physical activity levels to remain at or exceed peak values achieved during more favourable weather conditions. Strategies may include shifting to indoor activities or adapting to less favourable conditions (e.g. appropriate outdoor garments, more frequent but shorter duration periods of activity) (2) increasing dose/number of glucose-lowering medications during the winter and reducing these during the summer, in anticipation of seasonal variations (3) examining the impact of bright light therapy on activity and A1C among T2D patients with an increase in depressive symptomology when sunlight hours decline.

A prospective study of glycemic control during holiday time in type 2 diabetic patients

OBJECTIVE

In the U.K. Prospective Diabetes Study, A1C increased from 1.2 to 1.7% and fasting plasma glucose from 1.0 to 2.8 mmol/l over 10 years in type 2 diabetic patients. It is not known whether the blood glucose increase observed in long-term studies of type 2 diabetes results from small, steady increases throughout the year or from increases during discrete periods.

RESEARCH DESIGN AND METHODS

To estimate the variation of actual glycemic control and its relation to holiday times, we measured A1C and fructosamine in 110 patients with type 2 diabetes. These measurements were performed four times at intervals of 4-6 weeks; therefore, glycemic change was determined for three periods: preholiday period (from between November 13 and December 20 to between December 20 and January 20), holiday period (from between December 20 and January 20 to between January 28 and February 28), and postholiday period (from between January 28 and February 28 to between March 1 and April 10). A final measurement of A1C was obtained from 90 subjects in the following December or January.

RESULTS

The mean A1C increased, but not significantly, during the preholiday (increase 0.135 +/- 0.723%, P = 0.055) and holiday (increase 0.094 +/- 0.828%, P = 0.239) periods. The mean A1C decreased, but not significantly, during the postholiday period (decrease 0.022 +/- 0.588%, P = 0.695). Altogether, the A1C change during these three periods increased significantly (increase 0.207 +/- 0.943%, P = 0.024). The mean fructosamine increased significantly during the preholiday period (increase 0.151 +/- 0.460 mmol/l, P = 0.001), but there was no significant change during the holiday period (increase 0.057 +/- 0.593 mmol/l, P = 0.321). However, fructosamine decreased significantly during the postholiday period (decrease 0.178 +/- 0.448 mmol/l, P < 0.001). Altogether, the fructosamine changes during the study periods showed no significant difference (increase 0.030 +/- 0.566 mmol/l, P = 0.579). Between March or early April and the following December or January, there was no additional change in A1C (decrease 0.009 +/- 1.039%, P = 0.935) for the 90 participants who returned for follow-up treatment.

CONCLUSIONS

The present study demonstrates an influence of winter holidays on the glycemic control of patients who have type 2 diabetes, and this poor glycemic control might not be reversed during the summer and autumn months. Therefore, the cumulative effects of the yearly A1C gain during the winter holidays are likely to contribute to the substantial increase in A1C that occurs every year among type 2 diabetic individuals.