The combined effect on survival of four main behavioural risk factors for non-communicable diseases

• Smoking, alcohol, poor diet and inactivity are WHO's behavioural NCD risk factors.
• The combination of these four risk factors increased mortality about 2.5-fold.
• The chance to live 10 more years was 67% in 65-year-old men and 77% in women with all risk factors.
• Seventy-five-year-olds with no risk factors had the same chance to live another 10 years.
• In risk communication, the use of survival probabilities should be explored.

ObjectiveTo quantify and illustrate the combined effects of WHO's four behavioural risk factors for non-communicable diseases (NCDs) on mortality.MethodsParticipants (n = 16,721) were part of two Swiss population studies conducted between 1977 and 1993. Smoking status, alcohol consumption, physical activity and diet were assessed at baseline. With record linkage in 2008, up to 31 years of follow-up with 3,533 deaths could be recorded. Mortality was assessed with Cox proportional hazard models for each risk factor and their combinations. Ten-year survival probabilities for 65- and 75-year-olds were estimated with Weibull regression models.ResultsHazard ratios for the combination of all four risk factors compared to none were 2.41 (1.99–2.93) in men and 2.46 (1.88–3.22) in women. For 65-year-olds, the probability of surviving the next 10 years was 86% for men with no risk factors and 67% for men with four. In women, the respective numbers were 90% and 77%. In 75-year-olds, probabilities were 67% and 35% in men, and 74% and 47% in women.ConclusionsThe combined impact of four behavioural NCD risk factors on survival probability was comparable in size to a 10-year age difference and bigger than the gender effect.