Association of healthy lifestyle score with all-cause mortality and life expectancy: a city-wide prospective cohort study of cancer survivors

Adherence to a healthy lifestyle could reduce the cancer mortality in the western population. We conducted a city-wide prospective study in China investigating the association of a healthy lifestyle score with all-cause mortality and the life expectancy in cancer survivors.

Methods
This prospective cohort study included 46,120 surviving patients who were firstly diagnosed with cancer in Guangzhou. Five low-risk lifestyle factors including never smoking, never alcohol use, regular physical activity (≥ 2 h/week), sufficient sleep (≥ 6 h/day), and normal or high BMI (≥ 18.5 kg/m2) were assessed and a lifestyle score (0–5, a higher score indicates healthier lifestyle) was generated. Hazard ratios (HRs) of all-cause mortality and the life expectancy by levels of the lifestyle scores were estimated.

Results
Of 46,120 cancer survivors registered from 2010 to 2017, during an average follow-up of 4.3 years (200,285 person-years), 15,209 deaths were recorded. Adjusted HRs for mortality in cancer survivors with lifestyle score of 0–2, versus 5, were 2.59 (95% confidence interval (CI): 2.03–3.30) in women, 1.91 (95%CI 1.77–2.05) in men, 2.28 (95%CI 2.03–2.55) in those aged <65 years, and 1.90 (95%CI 1.75, 2.05) in those aged ≥ 65 years. Life expectancy at age 55 for those with a score of 0–2 and 5 was 53.4 and 57.1 months, respectively. We also found that cancer survivors with healthy lifestyle scores of 5 showed 59.9 months of life expectancy on average, which was longer than those with a score of 0–2.

Conclusion
Adopting a healthy lifestyle was associated with a substantially lower risk of all-cause mortality and longer life expectancy in cancer survivors. Our findings should be useful for health education and health promotion in primary care and clinical practice.

Peer Review reports
Background
China has about one fifth of global cancer cases [1, 2]. Although cancer survival has overall increased during the past decades [3], people with cancer had a shorter life expectancy than their peers without the disease [4], ranging from 2.4 to 11.2 years, depending on methods and study populations [4, 5]. Efforts to reduce morbidity and mortality of cancer, such as adherence to a healthy lifestyle, have been advocated in the general population based on published studies [6,7,8,9]. For example, previous studies showed that four major unhealthy lifestyle factors (i.e., cigarette smoking, heavy alcohol use, lack of physical activity, and unhealthy diet) contributed to at least 60% of premature deaths, leading to a loss of 7.4–17.9 years in life expectancy [6, 10,11,12]. However, in cancer survivors, whether adopting a healthy lifestyle will also have similar beneficial effects on life expectancy is unclear.

Hence, our study hereby explored the associations of the individual and combined healthy lifestyle factors with the risk of mortality in cancer survivors, and estimated the association of adherence to healthy lifestyles with life expectancy. Results of this study will facilitate evidence-based tertiary preventive strategies for providing holistic care and improving the quality of life in cancer survivors [13, 14].