HbA1c, fasting and 2 h plasma glucose in current, ex- and never-smokers: a meta-analysis.
OBJECTIVE
The relationships between smoking and glycaemic variables have not been well explored. We compared HbA1c, fasting plasma glucose (FPG) and 2 h plasma glucose (2H-PG) in current, ex- and never-smokers.


METHODS
This meta-analysis used individual data from 16,886 men and 18,539 women without known diabetes in 12 DETECT-2 consortium studies and in the French Data from an Epidemiological Study on the Insulin Resistance Syndrome (DESIR) and Telecom studies. Means of three glycaemic variables in current, ex- and never-smokers were modelled by linear regression, with study as a random factor. The I (2) statistic was used to evaluate heterogeneity among studies.


RESULTS
HbA1c was 0.10% (95% CI 0.08, 0.12) (1.1 mmol/mol [0.9, 1.3]) higher in current smokers and 0.03% (0.01, 0.05) (0.3 mmol/mol [0.1, 0.5]) higher in ex-smokers, compared with never-smokers. For FPG, there was no significant difference between current and never-smokers (-0.004 mmol/l [-0.03, 0.02]) but FPG was higher in ex-smokers (0.12 mmol/l [0.09, 0.14]). In comparison with never-smokers, 2H-PG was lower (-0.44 mmol/l [-0.52, -0.37]) in current smokers, with no difference for ex-smokers (0.02 mmol/l [-0.06, 0.09]). There was a large and unexplained heterogeneity among studies, with I (2) always above 50%; I (2) was little changed after stratification by sex and adjustment for age and BMI. In this study population, current smokers had a prevalence of diabetes that was 1.30% higher as screened by HbA1c and 0.52% lower as screened by 2H-PG, in comparison with never-smokers.


CONCLUSIONS
Across this heterogeneous group of studies, current smokers had a higher HbA1c and lower 2H-PG than never-smokers. This will affect the chances of smokers being diagnosed with diabetes.
CESP U1018, Inserm, 16 Avenue Paul Vaillant Couturier, 94807, Villejuif cedex, France.
Soraya
S
Soulimane
Dominique
D
Simon
William H
WH
Herman
Celine
C
Lange
Crystal M Y
CM
Lee
Stephen
S
Colagiuri
Jonathan E
JE
Shaw
Paul Z
PZ
Zimmet
Dianna
D
Magliano
Sandra R G
SR
Ferreira
Yanghu
Y
Dong
Lei
L
Zhang
Torben
T
Jorgensen
Jaakko
J
Tuomilehto
Viswanathan
V
Mohan
Dirk L
DL
Christensen
Lydia
L
Kaduka
Jacqueline M
JM
Dekker
Giel
G
Nijpels
Coen D A
CD
Stehouwer
Olivier
O
Lantieri
Wilfred Y
WY
Fujimoto
Donna L
DL
Leonetti
Marguerite J
MJ
McNeely
Knut
K
Borch-Johnsen
Edward J
EJ
Boyko
Dorte
D
Vistisen
Beverley
B
Balkau
D001786:Blood Glucose / Q000378:metabolism*; D005215:Fasting / Q000097:blood*; D006442:Glycated Hemoglobin / Q000378:metabolism*; D006801:Humans; D012907:Smoking / Q000097:blood* / Q000378:metabolism*
D001786:Blood Glucose; D006442:Glycated Hemoglobin