February 08, 2016
2 min read

Fasting plasma glucose levels higher in winter, extreme temperatures

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Chinese adults are more likely to have elevated fasting plasma glucose in the winter and spring compared with autumn and summer, according to recent findings.

Higher levels were also observed in extreme ambient cold and hot temperatures.

Shandy Li, PhD, a postdoctoral research fellow at the School of Public Health, University of Queensland, Brisbane, Australia, and colleagues analyzed data from 49,417 adults participating in the Kailuan study, a prospective, community-based analysis of current and retired employees of a Tangshan, China-based coal mining company (77.6% men; 9.5% aged 65 years; 3.1% with BMI 32 kg/m²; 7.9% with history of diabetes). City residents receive free biennial health examinations, including questionnaire assessment, blood work, urine analysis and biochemical tests. Each study participant returned for three follow-up visits between 2006 and 2011. Researchers downloaded daily meteorological data between 2006 and 2011 from the China Meteorological Data Sharing Service System and used generalized additive mixed models to examine the effects of temperature and seasonality on FPG levels while controlling for sex, age, BMI, diabetes status, exercise activity, alcohol intake and other variables.

Researchers found that FPG levels were higher in winter and spring than that in autumn and summer; FPG levels were highest in winter and lowest in autumn for all participants.

When compared with autumn levels, FPG levels in winter increased by a mean of 0.31 mmol/L (95% CI, 0.28-0.33). The difference was greater in participants with diabetes, according to researchers (P < .05), but there were no between-group differences based on sex or age.

The association between temperature and FPG levels was U-shaped. For all participants, the mean change in FPG levels associated with extreme cold temperature (6.7°C), moderate cold temperature (2.4°C), moderate hot temperature (23.7°C) and with extreme hot temperature (28.1°C), in comparison with the threshold temperature (18.1°C), were 0.12 mmol/L (95% CI, 0.1-0.14 mmol/L), 0.1 mmol/L (95% CI, 0.09-0.12), 0.06 mmol/L (95% CI, 0.04-0.08) and 0.12 mmol/L (95% CI, 0.08-0.16), respectively.

“Understanding the seasonality in markers, such as lipids, fibrinogen, blood pressure and FPG, is helpful to explore the reason for seasonality in the morbidity and mortality of diseases,” the researchers wrote. “Accumulating evidence has shown that FPG, lipids, fibrinogen and [BP] usually have a tendency to be higher in winter than in summer. Such seasonal variability might be driven from cold air temperatures, which increase activation of the sympathetic nerve system and secretion of catecholamine.” – by Regina Schaffer

Disclosure: The researchers report no relevant financial disclosures.