A decades-long study of Finnish adults found that a combination of known and unknown life-course factors contributes to the accumulation of chronic diseases across major organ systems.
The investigators collected detailed information on the health, lifestyle, and socioeconomic status of 2,003 participants who were born in Helsinki between 1934 and 1944. Participants also attended child welfare clinics, were living in Finland in 1971, and were in the random subsample of clinical investigations between 2001 and 2004. Medical records that spanned 30 years were analyzed to monitor the development of chronic conditions across cardiovascular, respiratory, metabolic, musculoskeletal, neurological, psychiatric, sensory, and gastrointestinal systems.
The study showed that about half of chronic disease accumulation could be explained by both measured and unmeasured factors. Most of the explained variation was due to unmeasured influences—unknown biological, environmental, or psychosocial factors that were not directly captured in the data.
Among measured variables, midlife clinical indicators such as body mass index (BMI), blood pressure, and fasting blood glucose were the strongest predictors. A higher BMI increased the risk of developing chronic conditions in five organ systems. Elevated blood glucose was linked to increased risk in four systems, including the heart and brain. Higher systolic blood pressure was associated with more cardiovascular and metabolic diseases.
Age was also a key factor: Each decade significantly increased the likelihood of accumulating additional conditions. Other influences included sex, birth order, wartime evacuation in childhood, and adult socioeconomic status. For example, participants who were evacuated during wartime developed respiratory diseases at higher rates later in life.
Lifestyle habits such as smoking, diet, alcohol use, and physical activity further affected disease accumulation. Current smokers had more than seven times the rate of respiratory diseases compared with nonsmokers. Greater physical activity and healthier diets were associated with fewer diseases in specific systems.
Still, these familiar risk factors explained only part of the variance. The upper limit of explainability was 75%, the authors–led by Markus JHaapanen,DMedSc, of the Folkhälsan Research Center in Helsinki–found. The researchers used statistical models to identify latent factors that grouped participants into eight profiles, each with distinct risks for multiple diseases. "The upper limit ranged from 24.5% to 86.3% by organ system, and was 48.3% across all diseases, indicating that although many chronic diseases share common risk factors, their predictive effect varies across organ systems," especially across cardiovascular and metabolic conditions, as well as neurological, psychiatric, and musculoskeletal disorders, they added.
The findings indicate that many chronic conditions do not develop independently but may stem from shared, often unmeasured, risk pathways. Although the study highlighted key modifiable risks, a large portion of disease accumulation remains unexplained.
The investigators suggested further research to identify additional contributors, including possible genetic predispositions, environmental exposures, or social stressors.
Full disclosures can be found in the published study.
Source: The Lancet
