Introduction

With the rapid ageing of the population in Europe, healthcare systems are facing increasing demand and patient load. Therefore, reliable estimates of the future development of the disease and disability burden as well as healthy and disease-free life years in the older sections of the population are crucial. At the same time, the future prospects of the health and functional ability of the working aged population are of critical importance as they must provide the necessary financial resources and manpower for maintaining and caring for the older population.

Non-communicable diseases (NCD) are the leading cause of mortality globally. About 71% of all deaths are related to NCDs, with cardiovascular disease (CVD) (eg, coronary heart disease, stroke), cancers, respiratory diseases and diabetes being the most frequent causes of NCD deaths.1 NCDs are also responsible for 28% of premature mortality, deaths under age of 70 years, in high-income countries. CVD, diabetes, cancers and chronic obstructive pulmonary disease (COPD) are among the most important causes of hospitalisations and absences from work.2

The burden of disease estimates for Finland for 2016 reported by the WHO in collaboration with the Institute of Health Metrics and Evaluation, include ischaemic heart disease (IHD), Alzheimer’s disease, cerebrovascular diseases and lung cancer within the top 10 causes of both disability adjusted life years (DALYs) and years of life lost (YLLs) to premature mortality (http://ghdx.healthdata.org/gbd-2016). For years lived with disability (YLDs) also diabetes was on the top-10 list (http://www.healthdata.org/finland). Thus, this group of potentially preventable NCDs poses a serious challenge to the economies of most countries and is responsible for remarkable economic burden to all European countries.3

A body of evidence indicates that lifestyles such as smoking, diet, alcohol use and physical activity have a major influence on health and longevity. The 10 leading risk factors contributing to the burden of disease in Finland are dietary habits, hypertension, obesity, alcohol and drug use, smoking, high fasting plasma glucose, high cholesterol, low physical activity and low glomerular filtration rate and low bone mineral density. It has been shown that adherence to a healthy lifestyle is associated with a lower risk of mortality. The relative risk of all-cause mortality declines proportionate to a higher number of healthy lifestyle factors.4 Lifestyles also make a large contribution to inequalities in health and functioning.5 6

Researchers from the EPIC-Norfolk prospective population study found that the combination of four behavioural risk factors, smoking, physical inactivity, alcohol drinking and low fruit and vegetable consumption, predicted a four-fold difference in the risk of dying over an average period of 11 years for middle-aged and older people.7 They also showed that the risk of death, particularly from CVD, decreases as the number of positive health behaviours increases. Results from the Healthy Ageing: a Longitudinal study in Europe (HALE) project indicated that adherence to a Mediterranean diet, non-smoking, moderate alcohol use and any physical activity among elderly were associated with a more than 50% lower rate of all-cause and cause-specific mortality.8 Lifestyle factors such as smoking, physical activity and obesity are also shown to be associated with healthy and disease-free life expectancy. In a recent large multi-cohort study, people with none of these three lifestyle-related risk factors were shown to have on average 8 years longer life expectancy in good health between the ages 50 and 75 years, compared with people with at least two of the three risk factors.9 Similarly, the European Society of Cardiology European Action on Secondary and Primary Prevention by Intervention to Reduce Events survey has shown that a large proportion of people at high risk for CVD have uncontrolled blood pressure, lipids and diabetes demonstrating the need for more effective prevention.10

Evidence based health policy planning requires the best available information on the future development of the main public health problems and how to influence this development. Ideally, health projections should take into account the history and current levels of health and its determinants as well as potential scenarios for changes in the health determinants in the total population and subgroups. Health projections based on different scenarios concerning the amenable determinants of public health have been produced, based on the Global Burden of Disease data or using the so called IMPACT model for coronary heart disease.11–13 However, the data sources available in Finland are much richer than those used in the Global Burden of Disease estimates. They can be used to improve the accuracy of the projections. In particular, the national health examination surveys with mortality and morbidity follow-up and re-examinations studies provide a unique data source which allows the projections to make use not only of the current levels of the risk factors but also the population and individual level changes from the past.

In 2017, a research project called the Projections of the burden of disease and disability in Finland – health policy prospects (PoDDy-HePo) was launched. The project was started in the end of 2017 and will be carried out until 2021. The overall aim of the project is to provide information about the long-term consequences of health related behaviours of the population and to what extent can the projected development of the burden of disease and disability be improved according to realistic scenarios about the development of risk behaviours in the total population and its subgroups. This information will help local, national and international governments and other policymakers to develop policies to address the growing problems of NCDs and inequalities, and to increase healthy life expectancy.

Making use of the wealth of relevant data sources available in Finland and novel statistical techniques, the project will provide up-to-date information about the prevalence of major chronic disease risk factors and the burden of disease, and health projections under different risk factor and policy scenarios in the Finnish population and its subgroups. Such data are highly relevant for policymakers and other stakeholders working in the field of public health and especially on prevention of chronic diseases. Statistical methods, which will be developed in the project, should be directly applicable to other countries with a comprehensive health monitoring system, such as Denmark, UK and the Netherlands. We will apply flexible statistical methods to account for interactions and non-linearities. For example, the random forest or non-parametric Bayesian methods allow combining time-to-event data obtained from registers with categorical or continuous variables commonly collected in surveys. The results will also facilitate the improvement of health projections in countries with less comprehensive health monitoring data.

Methods and analysis

The analyses of the PoDDy-HePo project will be based on existing data from cross-sectional and longitudinal health examination surveys (HESs) conducted between 1972 to 2017 in Finland, and register data from several administrative registers. Included HESs are based on random samples of the general population. They provide abundant information about biological and behavioural risk factors, and the health and morbidity of the population.

The project has two aims:

1. Estimation of the proportion of ill health attributable to modifiable risk factors, where the objectives are to

• understand determinants of the health inequalities and their changes over time, and to assess the contribution of modifiable risk factors to these inequalities;

• assess the impact of modifiable risk factors and their combinations to mortality and DALYs; and

• assess the impact of modifiable risk factors and their combinations on healthy life expectancy and disability and disease-free life years.

2. Providing projections of the incidence, prevalence and number of cases of major chronic disease and disability measures under different scenarios in the whole population and its subgroups. For this aim, the objectives are to

• assess and document the strengths and weaknesses of available projection methods;

• prepare statistical methods for projecting incidence, prevalence, life expectancy and expected healthy life years and the number of diseased individuals accounting for birth cohort differences and trends;

• account for sampling, parameter, model and prediction uncertainties in the projections using, for example, Bayesian predictive distributions or multiple imputation techniques;

• assess existing knowledge from randomised clinical trials (RCT) about intervention effects; and

• provide projections on health outcomes and risk factors.

Ethics and dissemination

All included surveys have followed the prevailing legislation and regulations of the time when they were conducted. Surveys since 1997 have been approved by the respective Ethics Committees at the time when the surveys were conducted (table 4). These ethical approvals cover the scope of this project. A written informed consent was obtained from survey participants, except for the early surveys which were conducted before the current legislation on medical research and the Helsinki Declaration. The participants of these early surveys were fully informed, they participated in the surveys voluntarily and the use of the data for medical and public health research was explained to them. These data can be used on the basis of the law on the National Institute for Health and Welfare (THL), which has a statement about the use of archived material (Act on the National Institute for Health and Welfare (668/2008)). Permissions for the record linkage have been obtained from relevant register owners.

The outputs of the project will include 8 to 10 scientific papers. The results will be disseminated through scientific publications, social media and conference or workshop presentations. Besides the scientific community, one of the key objectives is making the results available for the planning and evaluation of health policies.