1st August, 2018, Dr Chee L Khoo
We all know that unhealthy lifestyles are major risk factors for many chronic diseases and premature deaths. Many studies previously have reported that reduction in these unhealthy lifestyles can lead to increase in life expectancy of between 7.4 to 17.9 years in Japan, UK, Canada, Denmark, Norway and Germany 1-4. It would really be helpful during a consultation with our patients if we can quantify the benefit of these measures on the various chronic diseases and life expectancy.
A comprehensive analysis of the impact of adoption of lifestyle changes on life expectancy was performed recently on the US population. The uniqueness of the analysis was the source of the data. Researchers obtained data from the Nurses Health Study (NHS), Health Professional Follow up Study (HPFS), National Health and Nutrition Examination Survey (NHANES) and Centers for Disease Control and Prevention Wide-Ranging Online Data for Epidemiologic Research (CDC WONDER).
The NHS began in 1976, when 121 700 female nurses, 30 to 55 years of age responded to a questionnaire gathering medical, lifestyle, and other health-related information. In 1980, 92 468 nurses also responded to a validated food frequency questionnaire (FFQ). The HPFS17 was established in 1986, when 51 529 male US health professionals (dentists, optometrists, osteopaths, podiatrists, pharmacists, and veterinarians), 40 to 75 years of age completed a questionnaire about their medical history and lifestyle. They then used the NHANES 2013-2014 cohort to estimate the population distribution of lifestyle related factors. They used the CDC data to estimate death rates for comparison.
Diet in the NHS and HPFS was assessed every 4 years with a FFQ. Physical activity levels, body weight and smoking habits were updated every 2 years. Biennial questionnaires were used to collect information on potential confounders such as age, ethnicity, multivitamin use, regular aspirin use, postmenopausal hormone use (NHS only), and the presence or absence of a family history of diabetes mellitus, cancer, or myocardial infarction. 5 lifestyle-related factors: diet, smoking, physical activity, alcohol consumption, and BMI were considered but because this study was focused on modifiable lifestyle factors, they did not include clinical risk factors such as hypertension, hypercholesterolemia, or medication.
For physical activity, they classified low risk as >30 min/d of moderate or vigorous activities (including brisk walking) that require the expenditure of at least 3 metabolic equivalents per hour. They defined low-risk alcohol consumption as moderate alcohol consumption. For each low-risk factor, the participant received a score of 1 if they met the criterion for low risk. If the participant did not meet the criterion, he or she was classified as high risk for that factor and received a score of 0. The sum of these 5 scores provided a total number of low-risk factors of 0, 1, 2, 3, 4, or 5, with higher scores indicating a healthier lifestyle.
During a median of 33.9 years of follow-up of women and 27.2 years of follow-up of men, 42 167 deaths were recorded – 13 953 deaths resulting from cancer and 10 689 deaths from CVD. Each individual risk factor was positively and significantly associated with increased total, cancer and CVD mortality. Compared with those with the lowest scores (i.e. unhealthiest lifestyles), those with highest score (totally healthy) had hazard ratios (HR) of 0.26 for total mortality, 0.35 for cancer mortality and 0.18 for CVD mortality.
Another way of looking at the impact of unhealthy lifestyles is to look at their effect on life expectancy. Using these age- and sex-specific HRs, for those who were most unhealthy, they estimated the life expectancy at 50 years old to be 29.0 years for women and 25.5 years for men. For those with the most healthy lifestyles (highest scores of 5), they estimated the life expectancy at 50 years to be 43.1 years (i.e 14 years more) for women and 37.6 years (i.e. 12.1 years more).
In women, the gain in life expectancy came from 31% reduction in CVD deaths, 21% from reduction in cancer deaths and 48% from reduction in other deaths. In men, it was 34%, 23% and 43% respectively. They also observed a “dose-response” relationship between increasing number of healthy lifestyles and gain in life expectancy.
We already know the effect of healthy lifestyles on mortality but this study helps us quantify these numbers to our patients. Of course, healthy lifestyles not only increase life expectancy but also improve the quality of life which is not studied in this study.
Access the abstract here.
Reference:
- Tamakoshi A, Tamakoshi K, Lin Y, Yagyu K, Kikuchi S; JACC Study Group. Healthy lifestyle and preventable death: findings from the Japan Collaborative Cohort (JACC) Study. Prev Med. 2009;48:486–492. doi:10.1016/j.ypmed.2009.02.017.
- Khaw KT, Wareham N, Bingham S, Welch A, Luben R, Day N. Combined impact of health behaviours and mortality in men and women: the EPIC-Norfolk prospective population study. PLoS Med. 2008;5:e12. doi:10.1371/journal.pmed.0050012.
- Manuel DG, Perez R, Sanmartin C, Taljaard M, Hennessy D, Wilson K, Tanuseputro P, Manson H, Bennett C, Tuna M, Fisher S, Rosella LC. Measuring burden of unhealthy behaviours using a multivariable predictive approach: life expectancy lost in Canada attributable to smoking, alcohol, physical inactivity, and Diet. PLoS Med. 2016;13:e1002082. doi:10.1371/journal.pmed.1002082.
- O’Doherty MG, Cairns K, O’Neill V, Lamrock F, Jørgensen T, Brenner H, Schöttker B, Wilsgaard T, Siganos G, Kuulasmaa K, Boffetta P, Trichopoulou A, Kee F. Effect of major lifestyle risk factors, independent and jointly, on life expectancy with and without cardiovascular disease: results from the Consortium on Health and Ageing Network of Cohorts in Europe and the United States (CHANCES). Eur J Epidemiol. 2016;31:455–468. doi:10.1007/s10654-015-0112-8.
- Li K, Hüsing A, Kaaks R. Lifestyle risk factors and residual life expectancy at age 40: a German cohort study. BMC Med. 2014;12:59. doi:10.1186/1741-7015-12-59.
- Yanping Li, An Pan, Dong D. Wang, et al. Impact of Healthy Lifestyle Factors on Life Expectancies in the US Population. Circulation. 2018;CIRCULATIONAHA.117.032047, originally published April 30, 2018. https://doi.org/10.1161/CIRCULATIONAHA.117.032047