All-cause mortality
There was strong evidence that more physical activity and choosing better lifestyle behaviours led to longer survival in all 15 high quality studies examining all-cause mortality. However, the level of risk varied across different combinations of behavioural patterns. All studies found that a high adherence to positive factors including higher levels of physical activity, not smoking, eating healthy, and limited sedentary behaviour and alcohol consumption were strongly associated with reduced risk of all-cause mortality after long-term follow-up, and that this association was even stronger when these positive behaviours were combined [14, 17,18,19, 21,22,23, 27,28,29,30,31, 35, 37].
For example, Kvaaik and Colleagues (2010) found that after 20-years of follow-up, those in the healthiest category for all 4 lifestyle behaviours versus those in the least healthy category of lifestyle behaviours had a total mortality risk of 0.29 (CI = 0.19–0.43) [18]. Similarly, Prinelli and Colleagues (2015) followed subjects for an average of 17.4 years, and found that those with 1, 2, or 3 healthy behaviours had a significantly reduced risk of death of, 39, 56, and 73% respectively [14]. Petersen and Colleagues (2015) and McCullough and Colleagues (2011) both followed men and women for 14 years on average and found that every additional health recommendation adhered to, had a greater protective effect against mortality [31, 35]. Comparing lifestyle scores, Fazel-taber Malekshah and colleagues (2016) reported on observations from 40,708 participants, adults in the most healthy group had a significantly reduced risk of morality (RR = 0.68; CI = 0.54–0.86) compared to those in the least healthy group [15].
When examining the associations by different subgroups, McCullough and Colleagues (2011) limited their study to only non-smokers to explore in more detail the impact that following other prevention guidelines besides tobacco avoidance has on a cohort [35]. When examining all-cause mortality outcomes by sex, Larsson and Colleagues (2017) found that those with all four positive health behaviours compared to 0 had a reduced risk for men (RR = 0.47; CI = 0.44–0.51) and women (RR = 0.39; CI = 0.35–0.44) [22]. Similarly, Yun and colleagues (2012) found men and women with 4 healthy lifestyle factor points including high levels of physical activity compared to no healthy lifestyle factor points and no physical activity reported had a 0.50 (0.23–1.08) [19]. Behrens and Colleagues (2013) included a measure of adiposity in their lifestyle score and found that these results held, even with an additional measure [28]. Physical activity significantly reduced risk of mortality independently (RR = 0.86; CI = 0.84–0.89) with the larger the number of positive behaviours adhered to, the lower the risk, estimating that 33% of deaths were prevented if subjects adhered to all positive health behaviours. Examining the dual-associations between physical activity duration and history of smoking, O’Donovan and colleagues (2017) found those who exercised for over 60 min/week and were never smokers had a significantly reduced mortality risk compared to those who did no exercise and were current smokers, (RR = 0.29; CI = 0.24–0.36) [21].
Cardiovascular disease
A total of 14 high quality studies included a CVD outcome. This included 10 which examined CVD broadly [15, 16, 18, 21, 30, 31, 33, 35, 37, 38], 1 stroke incidence [32], 1 myocardial infarction [25], and 2 heart failure [24, 34]. Similar to the all-cause mortality findings, there was evidence that engaging in regular physical activity, and additional healthy behaviours was associated with a reduced risk for developing and dying of cardiovascular outcomes, and these finding were consistent across gender, age, and populations sampled. After 21 years of follow-up in a sample of 2096 participants, Eriksen and Colleagues (2015) found that the population attributable fraction for Coronary Heart Disease (CHD) and CVD amongst both Europeans (n = 1090) and South Asians (n = 1006) was 43% for CHD and 28% for CVD in Europeans and 63% for CHD and 51% for CVD in South Asians who did not have any of the four healthy behaviours surveyed at baseline [16]. Kvaanik and others (2010) looked at the influence of lifestyle on CVD over 20 years and found that the population attributable risk for CVD was 30%, and compared to those who did no physical activity and had the least healthy profile, individuals in the healthiest category had the greatest reduced risk 0.32 (CI = 0.15–0.69) [18]. In 40,708 participants comparing lifestyle scores over an 8-year follow-up period, those in the healthy group had a significantly reduced risk of CVD mortality (RR = 0.53, CI = 0.37–0.77) compared to those in the unhealthy group [15]. Hulsegge and Colleagues (2016) found that independent of baseline lifestyle behaviour reporting when re-measured later, each decrement in lifestyle factors was associated with a 35% higher risk of CVD, and individuals who maintained their healthy lifestyle over time (4 to 5 factors) had 2.5 times lower risk of CVD (HR = 0.43, CI = 0.25–0.63) compared to those who maintained an unhealthy lifestyle profile (0 to 1 factors) [23].
Examining various sub-groups, Petersen and Colleagues (2015) found a significant risk reduction amongst those men and women who achieved all five lifestyle behaviour points compared to those who did not [31]. For CVD mortality, the adjusted hazard ratio for those in the category of 4–5 positive lifestyle behaviours compared to those with 0 was 0.20 (CI = 0.14–0.0.29) for men and 0.21 (CI = 0.11–0.41) for women. In a population-based cohort of 60-year-old men (n = 2039) and women (n = 2193) after 11 years of follow-up, for those categorised as very healthy compared to unhealthy, the respective hazard ratios were 0.25 (CI = 0.15–0.44) for men and 0.35 (CI = 0.23–0.54) for women [30]. Examining men only (we excluded women because one of the scoring criteria included breastfeeding), Vergnaud and others (2013) found that after 12.8 years, men in the healthiest category compared to the least healthy category (RR = 0.64, CI = 0.50–0.82) were less likely to die of CVD [37]. Moreover, the largest study cohort (n = 111,966) found that achieving more recommended behaviours categorized as healthy compared to least healthy had a reduced risk of CVD mortality in both men (RR = 0.52, CI = 0.45–0.59) and women (RR = 0.42, CI = 0.35–0.51) over 14 years of follow-up [35].
When examining the dual-association between sedentary behaviour, specifically sitting time, and physical activity in women, Chomistek and Colleagues (2013) found a non-statistically significant interaction between sitting time and physical activity with CVD (pinteraction = 0.94) [33]. Similarly, O’Donovan and Colleagues (2017) examined the dual-associations between physical activity and smoking behaviour in 106,341 participants and found that after 9.4 years, those who were regular exercisers of over 60 min a week and did not smoke had a reduced risk of CVD mortality (RR = 0.27, CI = 0.18–0.42) compared to those who did not exercise and were current smokers [21].
Similar results were evident for heart failure when examining men and women separately [34]. Wang and Colleagues (2011) examined 18,346 men and 19,729 women and followed them for a median of 14.1 years. They found that for both men and women, having a healthier lifestyle profile resulted in a reduced risk of heart failure [34]. Having all 4 lifestyle factors compared to none, resulted in a hazard ratio of 0.31 (CI = 0.17–0.56) for men and, 0.19 (CI = 0.09–0.40) for women. In a sample of 33,966 men and 30,713 women followed for 13 years, the relative risks for heart disease in the healthiest lifestyle profile compared to the least healthy profile, which included those with 0 healthy lifestyle risk factors, was 0.38 (0.28–0.53) in men and 0.28 (0.19–0.41) in women [24]. For stroke, it was found that compared to the least healthy lifestyle profile (no lifestyle points), those with the healthiest profile (5 lifestyle points) had a relative risk of 0.38 (CI = 0.20–0.73) [32]. Finally, examining incident myocardial infarction in 20,721 men, followed for 11 years, having all 5 positive lifestyle points compared to none gave a relative risk of 0.14 (CI = 0.04–0.43), and these researchers concluded that this combination of positive behaviours could have prevented 79% (CI = 0.34–0.93%) of the events in this study cohort [25].
Cancers
A total of 12 studies assessed cancer as an outcome. Eight studies focused on cancer broadly [15,16,17, 21, 27, 31, 35, 37]. Three studies examined colorectal cancer [20, 26, 39], and one study examined breast cancer [36].
In general, engaging in a higher number of healthy behaviours compared to less, led to greater protection against most cancers. Kabat and Colleagues (2015) followed 476,396 participants for 10.5 years on average, during which time, 73,784 people had a first incident cancer diagnoses and 16,193 people died of cancer [27]. Similarly, in 40,708 participants after 8-years of follow-up, those in the healthy group compared to the least healthy group had a reduced risk of cancer mortality (RR = 0.82, CI = 0.53–0.86) [15]. Moreover, Kaavik and colleagues followed UK adults for 20 years where 18 deaths of 4886 deaths were attributed to cancer and they found that those participants with all positive health behaviours and those taking more physical activity versus those with no positive health behaviours and reporting no physical activity had a hazard ratio of 0.29 (CI = 0.15–0.60) [18].
Looking at subgroups, McCullough and others (2011) examined 111,966 non-smoking men and women and the relative risk for those in the healthiest category of lifestyle behaviour (7–8) versus those in the least healthy category (0–2) and found that risk was 0.70 (CI = 0.61–0.80) for men and 0.76 (CI = 0.65–0.89) for women [35]. This was similar to Vergnaud and Colleagues (2013) where men’s adjusted risk was 0.86 (CI = 0.69–1.07) for cancer after a median of 12.7 years of follow-up [37]. Additionally, after 10.3 years of follow-up of 59,941 Koreans, Yun and colleagues found that the risk for cancer mortality was 0.42 (CI = 0.35–0.69) in men and 0.50 (0.23–1.08) in women [19]. Petersen and colleagues (2015) explored cancer mortality risk in Danish men and women over a 14-year period and found that adherence to 4–5 positive lifestyle behaviours versus 0 positive lifestyle behaviours gave an adjusted hazard ratio of 0.33 (0.26–0.42) for cancer mortality in men and 0.41 (0.29–0.58) in women [31]. Lastly, O’Donovan and Colleagues (2017) examined the dual-associations between physical activity and smoking behaviour and found that regular exercisers who did not smoke had a greater reduced risk of cancer mortality (RR = 0.30, CI = 0.22–0.41) compared to those who never exercised and were current smokers [21].
Three cohort studies examined colorectal cancer specifically. In a sample of 59,503 men followed for 9.28 years, Zhang and Colleagues (2017) found that each increment in score in having a healthier lifestyle was associated with a 17% reduced risk of colorectal cancer (HR = 0.83; CI = 0.78–0.89), 27% for rectal cancer (HR = 0.73; CI = 0.66–0.82), and 10% for colon cancer (HR = 0.90; CI = 0.83–0.99) [20]. Kirkegaard and Colleagues (2010) found that higher physical activity levels and choosing more positive lifestyle behaviours was associated with a lower risk of colorectal cancer in a sample of 55,487 men and women, incidence rate ratio 0.89 (CI = 0.82–0.96) [26]. However, Nomura and Colleagues (2016) when examining incidence in African American women, found that adherence to more positive behaviours were not associated with colorectal cancer risk [39]. Lastly, the one cohort study examining breast cancer risk in postmenopausal women (n = 242,912) found that having a higher score of healthier behaviours (score of 4 compared to 1) reduced the risk of breast cancer incidence after a median of 10.9 years of follow-up (adjusted hazard ratio = 0.74, CI = 0.66–0.83) [36].
High quality studies
When we included more stringent criteria, restricting to studies with 8+ years of follow-up, and the use of a structured interview or a validated physical activity measure, we had 11 remaining studies (Table 2). Outcomes included in the final analysis were 7 for all-cause mortality, 6 for cardiovascular diseases, and 7 for cancers. Additionally, some studies performed subgroup analysis by sex, and others targeted only one sex specifically. Overall, trends suggested that engaging in a greater number of positive health behaviours resulted in reduced risk of death, and being less likely to develop and die of cardiovascular diseases, and cancers.
Table 2 Description of studies with a validated physical activity measure and 8+ years of follow-up (n = 11) Figure 2 examines the risk relationship between those in each cohort that were categorised as the healthiest (reference group) compared to those in the least healthy category. The results and evidence are quite strong that less healthy lifestyle behaviour puts one at a higher risk of death and cardiovascular disease incidence or mortality. Although the high-quality articles examining cancer outcomes displayed a similar trend to that seen in the all-cause mortality and CVD articles, the risk associations were not as large, and the findings for colorectal cancer were mixed.