Diabetes and tuberculosis: the impact of the diabetes epidemic on tuberculosis incidence.
BACKGROUND
Tuberculosis (TB) remains a major cause of mortality in developing countries, and in these countries diabetes prevalence is increasing rapidly. Diabetes increases the risk of TB. Our aim was to assess the potential impact of diabetes as a risk factor for incident pulmonary tuberculosis, using India as an example.


METHODS
We constructed an epidemiological model using data on tuberculosis incidence, diabetes prevalence, population structure, and relative risk of tuberculosis associated with diabetes. We evaluated the contribution made by diabetes to both tuberculosis incidence, and to the difference between tuberculosis incidence in urban and rural areas.


RESULTS
In India in 2000 there were an estimated 20.7 million adults with diabetes, and 900,000 incident adult cases of pulmonary tuberculosis. Our calculations suggest that diabetes accounts for 14.8% (uncertainty range 7.1% to 23.8%) of pulmonary tuberculosis and 20.2% (8.3% to 41.9%) of smear-positive (i.e. infectious) tuberculosis. We estimate that the increased diabetes prevalence in urban areas is associated with a 15.2% greater smear-positive tuberculosis incidence in urban than rural areas - over a fifth of the estimated total difference.


CONCLUSIONS
Diabetes makes a substantial contribution to the burden of incident tuberculosis in India, and the association is particularly strong for the infectious form of tuberculosis. The current diabetes epidemic may lead to a resurgence of tuberculosis in endemic regions, especially in urban areas. This potentially carries a risk of global spread with serious implications for tuberculosis control and the achievement of the United Nations Millennium Development Goals.
Stevenson
Catherine R
CR
Medical Research Council Epidemiology Unit, Cambridge, UK. n.c.unwin@ncl.ac.uk
Forouhi
Nita G
NG
Roglic
Gojka
G
Williams
Brian G
BG
Lauer
Jeremy A
JA
Dye
Chirstopher
C
Unwin
Nigel
N
D000328:Adult; D000368:Aged; D017281:Cost of Illness; D003920:Diabetes Mellitus / Q000453:epidemiology* / Q000503:physiopathology; D005260:Female; D006306:Health Surveys; D006801:Humans; D015994:Incidence; D007194:India / Q000453:epidemiology; D008297:Male; D008875:Middle Aged; D011159:Population Surveillance; D015995:Prevalence; D018570:Risk Assessment; D012307:Risk Factors; D012423:Rural Health / Q000706:statistics & numerical data* / Q000639:trends; D017678:Sex Distribution; D014397:Tuberculosis, Pulmonary / Q000453:epidemiology* / Q000209:etiology; D014504:Urban Health / Q000706:statistics & numerical data* / Q000639:trends