The duration of obesity and the risk of type 2 diabetes.
OBJECTIVE
The evidence for the association between obesity and the risk of type 2 diabetes has been derived mainly from the analysis of the degree of obesity. The role of the duration of obesity as an independent risk has not been fully explored. The objective of the present study was to investigate the association between the duration of obesity and the risk of type 2 diabetes.


METHODS
Prospective cohort study.


METHODS
The Framingham Heart Study (FHS), follow-up from 1948 to 1998.


METHODS
A total of 1256 FHS participants who were free from type 2 diabetes at baseline, but were obese on at least two consecutive of the study's twenty-four biennial examinations, were included. Type 2 diabetes status was collected throughout the 48 years of follow-up of the study. The relationship between duration of obesity and type 2 diabetes was analysed using time-dependent Cox models, adjusting for a number of covariates.


RESULTS
The unadjusted hazard ratio (HR) for the risk of type 2 diabetes for men was 1.13 (95 % CI 1.09, 1.17) and for women was 1.12 (95 % CI 1.08, 1.16) per additional 2-year increase in the duration of obesity. Adjustment for sociodemographic variables, family history of diabetes, health behaviour and physical activity made little difference to these HR. For women the evidence of a dose-response relationship was less clear than for men, particularly for women with an older age at obesity onset.


CONCLUSIONS
The duration of obesity is a relevant risk factor for type 2 diabetes, independent of the degree of BMI.
Abdullah
Asnawi
A
Department of Epidemiology and Preventive Medicine, Alfred Hospital, Monash University, Victoria, Australia. Asnawi.Abdullah@med.monash.edu.au
Stoelwinder
Johannes
J
Shortreed
Susan
S
Wolfe
Rory
R
Stevenson
Christopher
C
Walls
Helen
H
de Courten
Maximilian
M
Peeters
Anna
A
D000328:Adult; D000368:Aged; D000369:Aged, 80 and over; D015992:Body Mass Index; D015331:Cohort Studies; D003924:Diabetes Mellitus, Type 2 / Q000453:epidemiology* / Q000209:etiology; D005260:Female; D005500:Follow-Up Studies; D006801:Humans; D008297:Male; D008875:Middle Aged; D009765:Obesity / Q000150:complications / Q000453:epidemiology* / Q000473:pathology; D016016:Proportional Hazards Models; D011446:Prospective Studies; D012307:Risk Factors; D012720:Severity of Illness Index; D013997:Time Factors; D014481:United States / Q000453:epidemiology