Pairwise association of key lifestyle factors and risk of solid cancers - A prospective pooled multi-cohort register study.

Smoking, alcohol consumption, obesity, and physical inactivity are key lifestyle risk factors for cancer. Previously these have been mostly examined singly or combined as an index, assuming independent and equivalent effects to cancer risk. The aim of our study was to systematically examine the joint pairwise and interactive effects of these lifestyle factors on the risk of a first solid primary cancer in a multi-cohort prospective setting. We used pooled data from seven Finnish health survey studies during 1972-2015, with 197,551 participants diagnosed with 16,373 solid malignant primary tumors during follow-up. Incidence of any cancer was analyzed separately without and with lung cancers using Poisson regression with main and interaction effects of key lifestyle factors. When excluding lung cancer, the highest risk of any cancer in men was observed for smokers with a BMI of ≥25 kg/m2 (HR 1.36, 95 % CI 1.25-1.48) and in women for smokers consuming alcohol (HR 1.22, 1.14-1.30). No statistically significant interactions between any studied risk factor pairs were observed. When including lung cancer, the highest HRs among men were observed for smokers who consume alcohol (HR 1.72, 1.57-1.89) and among women for smokers who were physically inactive (HR 1.38, 1.27-1.49). Smoking combined with other lifestyle factors at any exposure level resulted in highest pairwise risks, both in men and women. These results highlight the importance of smoking prevention, but also the importance of preventing obesity and reducing alcohol consumption.

Pairwise association of key lifestyle factors and risk of colorectal cancer: a prospective pooled multicohort study.

BACKGROUND: Several lifestyle factors are associated with an increased risk of colorectal cancer (CRC). Although lifestyle factors co-occur, in most previous studies these factors have been studied focusing upon a single risk factor or assuming independent effects between risk factors. AIM: To examine the pairwise effects and interactions of smoking, alcohol consumption, physical inactivity, and body mass index (BMI) with risk of subsequent colorectal cancer (CRC). METHODS AND RESULTS: We used METCA cohort data (pooled data from seven population-based Finnish health behavior survey studies during years 1972-2015) consisting of 171 063 women and men. Participants' smoking, alcohol consumption, physical inactivity and BMI measures were gathered, and participants were categorized into those exposed and those not exposed. The incidence of CRC was modeled by Poisson regression with main and interaction effects of key lifestyle factors. The cohort members were followed-up through register linkage to the Finnish Cancer Registry for first primary CRC case until the end of 2015. Follow-up time was 1715, 690 person years. The highest pairwise CRC risk was among male smokers who had overweight (BMI ≥ 25 kg/m2 ) (HR 1.75, 95% CI 1.36-2.26) and women who had overweight and consumed alcohol (HR 1.45, 95% CI 1.14-1.85). Overall, among men the association of lifestyle factors and CRC risk was stronger than among women. In men, both having overweight and being a smoker combined with any other adverse lifestyle factor increased CRC risk. Among women, elevated CRC risks were observed for those who were physically inactive and who consumed alcohol or had overweight. No statistically significant interactions were detected between pairs of lifestyle factors. CONCLUSIONS: This study strengthens the evidence of overweight, smoking, and alcohol consumption as CRC risk factors. Substantial protective benefits in CRC risk can be achieved by preventing smoking, maintaining BMI to <25 kg/m2 and not consuming alcohol.

Lifestyle and cancer-a joint pairwise association of lifestyle habits with subsequent cancer diagnosis.

BACKGROUND: Unhealthy behaviours increase cancer risk. However, lifestyle habits co-occur and their joint association with cancer is not known. METHODS: A survey among midlife employees included data on lifestyle habits and covariates (N = 8960, response rate 67%, 80% women). The joint variables of lifestyle habits were prospectively linked with register data on cancer diagnosis (mean follow-up time 12.1 years). Cox proportional hazard model was used to calculate hazard ratios (HR), and their 95% confidence intervals. RESULTS: Smoking was associated with subsequent cancer risk and the association was strengthened by inactivity (HR 1.94, 1.46-2.59) and unhealthy diet (HR 1.92, 1.43-2.57). Smoking combined with both low (HR 1.70, 1.19-2.41) and moderate (HR 1.68, 1.27-2.23) alcohol consumption was also associated with increased cancer risk, as was unhealthy diet combined with moderate alcohol consumption (HR 1.55, 1.17-2.06) and inactivity (HR 1.44, 1.10-1.88). Inactivity combined with either low (HR 1.44, 1.06-1.96) or moderate (HR 1.47, 1.11-1.95) alcohol use was associated with subsequent cancer risk. CONCLUSIONS: Key unhealthy behaviours have additive effects. Preventive measures should be targeted to especially smokers and those having several adverse lifestyle habits.

The joint associations of smoking and obesity with subsequent short and long sickness absence: a five year follow-up study with register-linkage.

BACKGROUND: Both smoking and obesity are separately associated with sickness absence. Unhealthy lifestyle habits and health conditions may occur concurrently yet studies focusing on their joint association are few. This study examined the joint associations of smoking and obesity with sickness absence (SA). METHODS: A mail survey among employees of the City of Helsinki, Finland, during 2000-2002 included data on obesity, smoking and covariates (N = 8960, response rate 67%, 80% women). These data were prospectively linked with register data on self- (1-3 days) and medically certified (4 days or longer) SA among those consenting to the linkage (n = 6986). Pregnant, underweight and those with missing data on key variables were excluded (n = 138). The total number of participants included in the analyses was 6847. The follow-up time was 5 years. Poisson regression was used to calculate rate ratios (RR). RESULTS: Among women and men smoking and obesity were associated with self-certified SA. Among women there was a joint association with self-certified SA (obese smokers RR 1.81, 95% CI 1.59-2.07). Among women and men smoking and obesity were jointly associated with medically certified SA (for obese smoking women RR 2.23, 95% CI 1.93-2.57, for obese smoking men RR 2.69, 95% CI 2.03-3.55). Associations remained after adjustments for socioeconomic position, working conditions, health behaviours and self-rated health. CONCLUSION: Both smoking and obesity are jointly associated with all lengths of sickness absence. Support measures for smoking cessation and prevention of obesity could likely to reduce SA.