The impact of modifiable risk factors on mortality from prostate cancer in populations of the Asia-Pacific region.

Mortality from cancer of the prostate is increasing in the Asia-Pacific, when much of this region is undergoing a transition to a Western lifestyle. The role that lifestyle factors play in prostate cancer appears limited, but existing data mainly are from the West. We conducted an individual participant data analysis of 24 cohort studies involving 320,852 men (83% in Asia). Cox proportional hazard models were used to quantify associations between risk factors and mortality from prostate cancer. There were 308 deaths from prostate cancer (14% in Asia) during 2.1 million person-years of follow-up. The age-adjusted hazard ratio (95% confidence interval; CI) for men with body mass index (BMI) 28 kg/m2 or more, compared with below 25, was 1.55 (1.12 - 2.16); no such significant relationship was found for height or waist circumference. The BMI result was unchanged after adjustment for other variables, was consistent between Asia and Australia/New Zealand (ANZ) and did not differ with age. There was no significant relationship with diabetes, glucose or total cholesterol (p > or = 0.18). Smoking, alone, showed different effects in the two regions, possibly due to the relative immaturity of the smoking epidemic in Asia. In ANZ, the multiple-adjusted hazard ratio for an extra 5 cigarettes per day was 1.12 (95%CI: 1.03 - 1.22), whereas in Asia it was 0.77 (0.56 - 1.05). Body size is an apparently important determinant of prostate cancer in the Asia-Pacific. Evidence of an adverse effect of smoking is conclusive only in the predominantly Caucasian parts of the region.

The role of lifestyle risk factors on mortality from colorectal cancer in populations of the Asia-Pacific region.

Although colorectal cancer is one of the leading malignancies worldwide, there are few data on aetiological relationships from the Asia-Pacific region. Therefore, a collaborative study was conducted involving over half a million subjects from 33 cohort studies in the region. Age-adjusted death rates from colorectal cancer, over an average of 6.8 years follow-up, were 12 and 14 per 100,000 person-years among Asian women and men, respectively; corresponding values in Australasia were 31 and 41. Height was strongly associated with death from colorectal cancer: an extra 5 cm of height was associated with 10% (95%confidence interval, 3% - 18% additional risk, after adjustment for other factors. Smoking increased risk by 43% (9% - 88%), although no significant dose-response relationship was discerned (p>0.05). Other significant (p <0.05) risk factors were body mass index and lack of physical activity. There was no significant effect on colorectal cancer mortality for alcohol consumption, waist circumference, fasting blood glucose or diabetes, although the latter conferred a notable 26% additional risk. Height may be a biomarker for some currently unknown genetic, or environmental, risk factors that are related both to skeletal growth and mutanogenesis. Understanding such mechanisms could provide opportunities for novel preventive and therapeutic intervention.