(12-06-13) Body-mass index and cause-specifi c mortality in 900 000 adults: collaborative analyses of 57 prospective studies

Prospective Studies Collaboration*
Summary
Background The main associations of body-mass index (BMI) with overall and cause-specifi c mortality can best be
assessed by long-term prospective follow-up of large numbers of people. The Prospective Studies Collaboration aimed
to investigate these associations by sharing data from many studies.
Methods Collaborative analyses were undertaken of baseline BMI versus mortality in 57 prospective studies with
894 576 participants, mostly in western Europe and North America (61% [n=541 452] male, mean recruitment age
46 [SD 11] years, median recruitment year 1979 [IQR 1975–85], mean BMI 25 [SD 4] kg/m²). The analyses were
adjusted for age, sex, smoking status, and study. To limit reverse causality, the fi rst 5 years of follow-up were excluded,
leaving 66 552 deaths of known cause during a mean of 8 (SD 6) further years of follow-up (mean age at death
67 [SD 10] years): 30 416 vascular; 2070 diabetic, renal or hepatic; 22 592 neoplastic; 3770 respiratory; 7704 other.
Findings In both sexes, mortality was lowest at about 22·5–25 kg/m². Above this range, positive associations were
recorded for several specifi c causes and inverse associations for none, the absolute excess risks for higher BMI and
smoking were roughly additive, and each 5 kg/m² higher BMI was on average associated with about 30% higher
overall mortality (hazard ratio per 5 kg/m² [HR] 1·29 [95% CI 1·27–1·32]): 40% for vascular mortality (HR
1·41 [1·37–1·45]); 60–120% for diabetic, renal, and hepatic mortality (HRs 2·16 [1·89–2·46], 1·59 [1·27–1·99], and
1·82 [1·59–2·09], respectively); 10% for neoplastic mortality (HR 1·10 [1·06–1·15]); and 20% for respiratory and for all
other mortality (HRs 1·20 [1·07–1·34] and 1·20 [1·16–1·25], respectively). Below the range 22·5–25 kg/m², BMI was
associated inversely with overall mortality, mainly because of strong inverse associations with respiratory disease and
lung cancer. These inverse associations were much stronger for smokers than for non-smokers, despite cigarette
consumption per smoker varying little with BMI.
Interpretation Although other anthropometric measures (eg, waist circumference, waist-to-hip ratio) could well add
extra information to BMI, and BMI to them, BMI is in itself a strong predictor of overall mortality both above and
below the apparent optimum of about 22·5–25 kg/m². The progressive excess mortality above this range is due
mainly to vascular disease and is probably largely causal. At 30–35 kg/m², median survival is reduced by 2–4 years; at
40–45 kg/m², it is reduced by 8–10 years (which is comparable with the eff ects of smoking). The defi nite excess
mortality below 22·5 kg/m² is due mainly to smoking-related diseases, and is not fully explained.
Funding UK Medical Research Council, British Heart Foundation, Cancer Research UK, EU BIOMED programme,
US National Institute on Aging, and Clinical Trial Service Unit (Oxford, UK).


Source: Lancet 2009; 373: 1083–96

News

---

In evidenza

"L'informazione presente nel sito serve a migliorare, e non a sostituire, il rapporto medico-paziente."

Per coloro che hanno problemi di salute si consiglia di consultare sempre il proprio medico curante.