Background It is well established that higher body mass index (BMI) is associated with greater risk of many individual chronic conditions. Little is known about the role of BMI in the accumulation of multiple chronic conditions (multimorbidity) across the adult lifespan. We aimed to prospectively quantify the association between time-varying BMI and accumulation of chronic conditions in three age-group cohorts.
Methods We included 31,609 women (10,582 born in 1973-78, 12,355 born in 1946-51, and 8672 born in 1921-26) from the Australian Longitudinal Study on Women’s Health who were followed up approximately every 3 years from 1996. Generalized estimated equations was used to calculate the odds ratio (OR) and 95% confidence interval (CI) for cumulative incidence of nine chronic conditions in relation to time-varying BMI, age group and disease history.
Results A U-shaped pattern in the association of BMI with number of chronic conditions was observed in 1946-51 and 1926-21 Cohorts. Women who were obese experienced a marked accumulation of additional chronic conditions after they became multimorbid. Compared to women with normal weight and no chronic conditions, adjusted ORs for developing two or more new chronic conditions in obese women were 2.7 (95% CI, 2.4-3.0), 3.3 (95% CI, 2.8-3.8) and 5.3 (95% CI, 4.6-6.0) for those with no chronic conditions, one chronic condition, and multimorbidity, respectively. These results were consistent across the three age-group cohorts.
Conclusion Overweight and Obesity are associated with the accumulation of chronic conditions. This effect appears to be consistent among young, middle-aged and older adult women.