Association between smoking, insulin resistance and beta-cell function in a North-western First Nation.
OBJECTIVE
Aboriginal peoples have a high prevalence of smoking and are at major risk for diabetes. The role of insulin resistance vs. compromised beta-cell function in the link between smoking and glycaemic disease is not clear. This study tested whether relations between insulin resistance and beta-cell function differ between current smokers, former smokers and non-smokers, and if having diabetes modifies smoking-related effects.


METHODS
A community-based diabetes screening initiative was mounted for a North-western First Nation (Interior Salishan) in rural British Columbia, Canada. Respondents were on-reserve Aboriginal people (n=156), all adults 18+ years. Glycaemic status was determined by oral glucose tolerance test. Fasting values for glucose and insulin were used to estimate beta-cell function and insulin resistance by homeostasis model assessment (HOMA). Analyses adjusted for age, sex, alcohol intake, education, body mass index and physical activity.


RESULTS
For normoglycaemic persons (n=119) current smokers relative to non-smokers had high beta-cell values [difference (95% confidence interval) 19.5 (17.1, 21.9)], while former smokers had low beta-cell values [difference -22.8 (-20.3, -25.3)] (P<0.0001). For diabetic persons (n=37) differences were of equivalent direction but greater magnitude (P<0.0001). Insulin resistance was for normoglycaemic persons highest for current smokers, and for diabetic persons lowest for current smokers (P=0.021).


CONCLUSIONS
Former smoking is associated with low beta-cell function, and current smoking with high beta-cell function, independent of diabetes in the North-western First Nation surveyed. Associations between smoking and insulin resistance vary according to glycaemic status. Smoking may have diametric acute and post-cessation effects on beta-cell function and insulin resistance.
Département de médecine sociale et préventive, Faculté de médecine, Université de Montréal, Québec, Canada. mark.daniel@umontreal.ca
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Cargo
D000328:Adult; D000368:Aged; D001955:British Columbia / Q000208:ethnology; D003924:Diabetes Mellitus, Type 2 / Q000208:ethnology* / Q000503:physiopathology; D005260:Female; D006801:Humans; D007198:Indians, North American; D007333:Insulin Resistance / Q000502:physiology*; D007515:Islets of Langerhans / Q000502:physiology*; D008297:Male; D008875:Middle Aged; D015999:Multivariate Analysis; D012907:Smoking / Q000208:ethnology*