▎ WuXi AppTec content team editor
Obesity is a common risk factor for many diseases in middle-aged and older adults. In older people over the age of 65, it is common to have at least two diseases occurring simultaneously (multiple diseases), such as diabetes, gout, and hypertension. Some people may even have four or more diseases occurring at the same time (complex multiple diseases). So to what extent is obesity related to the development of complex multi-morbidity?
A recent study published in The Lancet Diabetes & Endocrinology suggested that obesity is linked to 21 major diseases and that these diseases are interrelated. Compared with the normal weight population, the risk of complex multimorbidity in obese people is about 12.4 times higher. And the more severe the obesity, the higher the risk of future disease.
Screenshot source: The Lancet Diabetes & Endocrinology
To provide a more comprehensive assessment of the complex multiple diseases associated with obesity, the investigators analysed pooled data from multiple cohort studies in Finland (average follow-up time of 12.1 years) and the United Kingdom (average follow-up time of 11.8 years). The study was first analysed based on Finnish cohort data (114657 participants with an average age of 42.6 years at start of the study) and the findings were subsequently validated in the UK cohort (499357 participants, with an average age of 57.0 years at start of the study).
At the beginning of the study, the investigators divided the participants into the following 4 categories based on their weight:
Obesity: BMI≥ 30.0kg/m2. Obesity is further divided into grade 1 obesity (BMI 30.0kg/m2 ~ 34.9 kg/m2), grade 2 obesity (35.0 kg/m2 ~ 39.9 kg/m2) and grade 3 obesity (≥40kg/m2).
Overweight: BMI of 25.0 kg/m2 ~ 29.9 kg/m2;
Normal weight: BMI of 18.5kg/m2 ~ 24.9kg/m2;
Underweight: BMI2.
Investigators correlated health data, analyzing participants' BMI associated with risk of multiple morbidity (assessed by risk ratio [HR]), and the proportion of obesity in the cause of the disease (assessed by population attribution score [PAF]).
Image credit: 123RF
After adjusting for mixed factors such as educational background, smoking, diet and living habits, the researchers' analysis found that:
Obesity is highly correlated with 21 diseases (HR≥1.50, p
And these 21 diseases are also highly correlated, so the presence of each disease increases the risk of developing another disease, which can also be predicted or predicted by other obesity-related diseases. This interconnectedness accelerates the development of obesity-related multimorbidity, and the greater the degree of obesity, the greater the relative risk of complex multimorbidity.
Among obese and complex multimorbidity patients, the most common obesity-related diseases are: adult diabetes mellitus (75.4%), hypertension (71.8%), sleep disorders (42.6%), osteoarthritis (42.1%), arrhythmias (34.4%), bacterial infections (31.3%) and asthma (22.1%), which are both a single disease and part of complex multimorbidity.
Compared with people of normal weight, obese people have a nearly 3 times higher risk of at least one obesity-related disease (HR = 2.83), 5 times the risk of two related diseases (HR = 5.17), and about 12.4 times the risk of complex multiple diseases (HR = 12.39). Among the complex multi-morbidities, 55.2% of cases are due to obesity (PAF = 55.2%).
Obesity can cause people to develop multiple diseases at a younger age than normal weight. This effect of obesity begins to manifest around the age of 30, with an increase in common multimorbidity; complex multimorbidity begins to increase at about 45 years of age, and the effect persists with age. For example, the proportion of people who are obese at the age of 55 is similar to the proportion of complex multiple diseases in people with normal weight at the age of 75.
Moreover, the degree of obesity and the risk of complex multimorbidity are dose-reactive. Specifically:
People with grade 3 obesity are at higher risk of developing complex multiple diseases in the future than people with grade 1 obesity.
Compared with obese people, the risk of complex multiple diseases in the future is relatively small, 2.67 times that of people with normal weight (HR = 2.67). Of the complex multiplicities in overweight people, 13.3% of cases are attributable to overweight. （PAF=13.3%）。
In addition, the overall risk of all-cause death increased by 32% in obese people (HR=1.32), and the risk of death increased by 90% in people with grade 3 obesity (HR=1.90).
The researchers conclude that this correlation suggests that interventions in obesity are an appropriate way to prevent complex multimorbidity. Developing healthy lifestyle habits and reducing risk factors for obesity is a simple way to reduce complex and multi-morbidity in people; treatments such as drug therapy and bariatric surgery can also prevent patients from suffering from complex and multi-morbidity.