Aims/hypothesis Latent autoimmune diabetes (LADA) is a common form of diabetes, yet the risk factors are poorly characterised. The aim of this study was to investigate the influence of age, overweight and physical activity on the risk of LADA. Methods We analysed age, overweight and physical inactivity and the incidence of LADA in 38,800 men and women, observed between 1984 and 1986 and 1995 and 1997 as part of the Nord-Trøndelag Health Survey. We also compared such factors with incident cases of type 2 (n=738) and 'classic' type 1 diabetes (n=18). Patients classified as LADA (n=81) had antibodies against GAD and were insulin independent at diagnosis. Results The proportion of those who were older, overweight and inactive before diagnosis was almost identical in LADA and type 2 diabetes patients. BMI ≥30 kg/m 2 was strongly associated with LADA incidence (relative risk [RR]=15.0, 95% CI 7.51-29.97). The association was similar for type 2 diabetes (RR=15.37, 95% CI 12.07-19.57) but not for type 1 diabetes. Similarly, age (≥60 years) was an important risk factor for LADA (RR= 5.62, 95% CI 2.36-13.4) as well as for type 2 diabetes (RR=6.78, 95% CI 5.07-9.06) in contrast to type 1 diabetes. Physical inactivity was associated with an increased risk of both LADA and type 2 diabetes. Conclusions/interpretation This study suggests that increased age, overweight and physical inactivity are as strong risk factors for LADA as for type 2 diabetes. These findings suggest a role for insulin resistance in the pathogenesis of LADA.Keywords Age . Epidemiology . Incidence . Latent autoimmune diabetes in adults . Overweight . Physical inactivityAbbreviations AP attributable proportion LADA latent autoimmune diabetes in adults RR relative risk Diabetologia (2007) 50:55-58