Risk factors measured during the human life span and latent factors account for up to three quarters of multimorbidity from middle to old age. Even though known risk factors account for a significant share of disease accumulation, more than half of such accumulation remains unexplained.
As the population ages, multimorbidity, or when a patient has multiple diseases at once, is becoming increasingly common. The onset of one disease increases the risk of developing other diseases, making it necessary to investigate how a range of risk factors together affect such accumulation. Prior studies have focused on individual risk factors and related individual diseases.
Now, a study explored how the risk factors measured from birth to middle age and unmeasured, or latent, factors covering the entire life span predict and explain the incidence of chronic diseases in eight organ systems from middle to old age: the cardiovascular, metabolic, gastrointestinal, musculoskeletal, respiratory, neurological and psychiatric systems, and the sensory organs.
The study analysed 22 risk factors, including age, sex, early life (e.g., size at birth, early childhood growth, childhood wartime evacuee status), socioeconomic factors (e.g., socioeconomic status in childhood, income in adulthood), lifestyle factors (e.g., smoking, alcohol consumption, physical activity, diet), clinical measurements and biomarkers (e.g., body mass index, blood pressure, blood glucose).
In addition, latent factors affecting the development of diseases were investigated. While these factors affect disease accumulation in the same way as known risk factors, they are not yet sufficiently known or had not been measured in the study. Examples of potential latent factors include air pollution as well as genetic and other environmental factors.
Key findings
- Measured and latent factors together accounted for up to three quarters of the incidence of chronic diseases in different organ systems.
- Age, body mass index, high blood pressure (hypertension) and high blood glucose levels (hyperglycaemia) explained disease onset in several organ systems.
- Body mass index, hypertension, hyperglycaemia, smoking, alcohol consumption, physical activity and diet together accounted for roughly 40% of the cases associated with the factors measured in the study.
- Latent factors played a significant role in disease incidence, indicating that some risk factors underlying diseases remain unknown.
Personal choices matter
"While individuals can affect their risk of developing a disease in terms of body mass index, blood pressure, blood glucose, smoking, alcohol consumption, physical activity and nutrition, the findings emphasise the need to influence these factors also at the national level to prevent diseases," Docent Markus Haapanen says.
"The relevance of latent factors highlights the need to identify new risk factors in the future," he adds.
The incidence of diseases was monitored from middle to old age using national registry data. The research group was composed of 2,000 people born between 1934 and 1944 in the Helsinki birth cohort.
