Body mass index and waist circumference in relation to the risk of 26 types of cancer: a prospective cohort study of 3.5 million adults in Spain

A new prospective study by scientists from the International Agency for Research on Cancer (IARC), in collaboration with researchers from the Fundación Instituto Universitario para la Investigación en Atención Primaria de Salud Jordi Gol i Gurina (IDIAPJGol) in Barcelona, Spain, found that a higher body mass index (BMI) was associated with a higher risk of developing 12 cancer types. 

The results include new evidence for an increased risk of developing four haematological cancers and, among never smokers, an increased risk of developing head and neck cancers. The study was published in the journal BMC Medicine. 

The study included 3 658 417 participants, of whom 202 837 were diagnosed with cancer during the follow-up period. A higher BMI was positively associated with increased risk of developing cancers of the corpus uteri, kidney, gallbladder and biliary tract, thyroid, colorectum, and breast (in postmenopausal women), as well as multiple myeloma, leukaemia, and non-Hodgkin lymphoma.

After the analyses were restricted to never smokers to account for incomplete adjustment for smoking, a higher BMI was also positively associated with risk of Hodgkin lymphoma, cancers of the head and neck, and cancers of the brain and central nervous system. The researchers also found associations in the overall cohort between BMI and the risk of prostate cancer and the risk of cancers of the head and neck; oesophagus; larynx; and trachea, bronchus, and lung. This probably indicates residual confounding by smoking, because the strength of these associations drastically changed among never smokers, except for prostate càncer