UICC World Cancer Congress Melbourne, Australia 6 December 2014

Transcription

1 Ethnic differences, obesity and cancer, stages of the obesity epidemic and cancer prevention Professor TH Lam, JP, BBS MD, FFPH, FFOM, Hon FHKCCM, FHKAM, FRCP Sir Robert Kotewall Professor in Public Health School of Public Health The University of Hong Kong UICC World Cancer Congress Melbourne, Australia 6 December 2014

2 Outline Obesity and ethnic differences Obesity and cancer: the evidence Stages of the obesity epidemic Conclusions

3 What is Obesity? Body weight, body fat and body fat percent (BF%) BMI most commonly used for general obesity: only data available in most studies Waist circumference (and WHR): central obesity: data available only in more recent studies Cannot distinguish between lean mass and fat mass Different methods to measure body fat: all with limitations

4 Racial/Ethnic Differences: BF%/BMI Relationships between BF% and BMI differ between ethnic groups Asians: higher BF% at a lower BMI compared to Caucasians Not all Asians are equal: Chinese, Indonesians of Malays ancestry and Thais Not all Chinese are equal: New York, Beijing and Hong Kong Universal BMI cut-off points not appropriate (Deurenberg et al 2002 )

5 Extraneous and life course factors Many studies were not specifically designed to compare ethnic/racial differences Ethnic/racial differences could be explained by extraneous factors: regional, socioeconomic developments (high, middle and low income countries, or regions within the same countries): gradual developments in many decades versus recent rapid developments; immigration, inter-generational differences Life course differences (e.g. early life events, weight gain from birth to middle age)

6 Obesity and cancer: the evidence First Expert report Second Expert report Continuous Update Project Oesophagus C - Pancreas C C Gallbladder? P - Liver? - Colorectum? C C Breast pre-m P ( ) P ( ) Breast post-m P(breast) C C Endometrium C C C Kidney P C - Ovary - - P Prostate (advanced) - - P C = Convincing P = Probable? Possible 1997; Limited 2007

7 BMI and cancer Cancer BMI RR of increased body WCRF Increment fatness (95% CI) report date Prostate(advanced) 5 kg/m ( ) 2014 Ovarian 5 kg/m ( ) 2014 Endometrial 5 kg/m ( ) 2013 Pancreatic 5 kg/m ( ) 2012 Colorectal 1 kg/m ( ) 2011 Postmenopausal breast 2 kg/m ( ) 2010 Premenopausal breast 2 kg/m ( ) 2010 Kidney 5 kg/m ( ) 2007 Gallbladder 5 kg/m ( ) 2007 Oesophageal no analysis 2007

8 Obesity and cancer: ethnic differences? APCSC 2010 BMI and cancer mortality 39 cohorts, 424,519 people (77% Asian) 4,872 cancer deaths from 401,215 (excluding FU <3y) No regional differences in HR for cancer and BMI except oropharynx and larynx: inverse in ANZ, absent in Asia Asian data: mainly from Japan Insufficient data on WC, WHR Test of regional interaction (heterogeneity): low stat. power (Parr 2010)

9 Number (millions) Cancer is increasing Estimated global number of new cases of cancer (actual and predicted) Year Data from Parkin et al, Pisani et al, Globocan 2012, IARC

10 Obesity is increasing Adults ( 20), BMI 25 kg/m 2 (OW/OB) Prevalence: Men: 28.8% to 36.9% (by 28.1%; 0.62 percentage point/y) Women: 29.8% to 38.0% (by 27.5%; 0.63 percentage point/y) No. of OW/OB people: 875 to 2100 million; increased by 240% Prevalence of OB increasing in both developed and developing countries 2013: higher in women in developed and developing countries Rate of increase of OW/OB greatest ; slowed down in the past decade, esp. developed countries (Ng 2014)

11 Obesity increasing Children & adolescents (2-19), Prevalence of OW/OB: Developed Boys 16.9% to 23.8% (by 40.8%; 0.53 percentage point/y) Girls 16.2% to 22.6% (by 39.5%; 0.49 percentage point/y) Developing Boys 8.1% to 12.9% (by 59.3%; by 0.37 percentage point/y) Girls 8.4% to 13.4% (by 59.5%; by 0.38 percentage point/y) In both developed & developing, small sex differences in levels and trends (Ng 2014)

12 Global health challenge No national success stories in 33 years (no significant decreases in obesity) Wide variation in rates of increase from the same initial level Epidemic might have peaked in developed countries Others might not reach 40+% as in some developing countries (Ng 2014)

13 Can we learn from the stages of the epidemic of tobacco?

14 Four stages tobacco epidemic model

15 Four stages obesity epidemic model ß ß We are here à à Hypotheses for obesity epidemic Stage 1: Prevalence of obesity up to 20%; 5% death; >30 years. Stage 2: Rapid increase in obesity to a peak of 60%; 10% death.; 30 years. Stage 3: Downturn in obesity to 30%; deaths peak at 30% death; 40 years. Stage 4: Prevalence and death slowly decreasing to 10%; >60 years.

16 The epidemic curves are the same for men and women The West and some LMIC: Early stage, Stage 2 Rising, high obesity level Rising mortality LMIC: Early stage 1 Early rise of obesity Low, or early rise of mortality Stages of obesity epidemic? A gap of 40 years between peak of obesity (60%) and peak of death (30%)

17 World Cancer Research Fund International: Estimates of preventable fraction of specific cancer sites from body fatness Cancer USA (%) UK (%) Brazil (%) China (%) Oesophagus Pancreas Gallbladder Colorectum Breast Ovarian Endometrium Kidney Source: facts- figures/preventability- es:mates/cancer- preventability- es:mates- body- fatness

18 Prevention and obesity control A greater and more complex challenge than tobacco control 1. We advocate for a Framework Convention on Obesity Control (FCOC) 2. The MPOWER strategies against tobacco are immediately applicable by replacing the word tobacco with obesity 3. We need results on health benefits (risk reversal) from obesity reduction

19 F C O C - MPOWER Monitor obesity and prevention policies Protect people from obesity Offer help to quit obesity Warn about the dangers of obesity Enforce bans on obesity advertising, promotion and sponsorship Raise taxes against obesity

20 Conclusions Ethnic differences on BF%/BMI; but not clear on the association between obesity and cancer Obesity, cancer and evidence that obesity causes cancer increasing Now at early stages of obesity epidemic: risks and disease burden under-estimated Life course research needed Much can be prevented: MPOWER and FCOC Health benefits from obesity reduction: decades later

21 For further information Professor TH Lam The School of Public Health University of Hong facebook.com/wcrfint Acknowledgements: Many thanks to World Cancer Research Fund International. A full version of this presentation will be available on their website.