Global Burden of Disease worldwide statistical analysis of risk factors impacting noncommunicable disease deaths compared with assessments by systematic literature reviews
Authors: Cundiff David K , Wu Chunyi 
Published: December 2020

Background

Based on systematic literature reviews, the Institute of Health Metrics and Evaluation (IHME) Global Burden of Disease (GBD) landmark risk factor paper attributes about 8 million noncommunicable diseases deaths/year to a composite of 15 dietary risk factors. Another 27 million noncommunicable deaths out of 56.5 million total deaths worldwide are attributed to high levels of metabolic risk factors.

Methods

We format and population weight IHME GBD worldwide data resulting in7886 rows of data from cohorts of about 1 million people each representing about 7.8 billion people in 2020. Noncommunicable disease deaths/100k/year (NCD) are correlated with the four metabolic risk factors, 15 dietary risk factors, six dietary covariates, and the composite “dietary risks” variable. We compare NCD groups of cohorts (about 1000 cohorts, representing about 1 billion people) with the lowest and highest NCD and the same for body mass index (BMI). We compare literature reviews attributions of NCD causation with findings from the GBD data in assessing the impact of dietary and metabolic risk factors on NCD.

Findings

Literature review derived dietary risks composite risk factor correlated with NCD account for 1.9% of worldwide NCD. Using GBD data to compare groups with the lowest versus the highest rates of NCD: the lowest NCD 990 cohorts average 923.8 NCD and consume 320.4 kcal/day from six animal foods. The highest NCD 1054 cohorts average 2064 NCD and on average and consume 117.2 kcal/day of six animal foods. Vitamin A deficiency in children is 75% higher in children in the high NCD cohorts. Evaluating high BMI cohorts, 973 cohorts with BMI≥25 account for 10.5% of the worldwide NCD. These high BMI cohorts also have higher than average fasting plasma glucose (FPG: FPG mean=4.71 versus FPG mean=4.25) and low density lipoprotein cholesterol (LDLC: LDLC mean=2.79 versus LDLC mean=2.30).

Interpretation

The evidence basis of the dietary risks composite risk factor, accounting for only 1.9% of NCD worldwide should be questioned. Systematic literature reviews based versus GBD data based estimates of metabolic and dietary risk factor impacts on NCD vary markedly. Systematic literature reviews of studies involving individual subjects are better at ascertaining the impact on NCD of obesity, hyperglycemia, high LDLC, and hypertension. High levels of metabolic risk factors cannot be analysed with GBD data giving only the mean values for NCD and risk factors. Since high mean BMI cohorts (mean BMI≥25) account for only 10.5% of worldwide NCD, literature reviews appear to overestimate the worldwide impacts of high metabolic risk factors on NCD (i.e., accounting for nearly 50% of worldwide deaths: 27 million/56.5 million worldwide deaths). High NCD, including cardiovascular disease deaths, associated with low animal food intake suggests that fat soluble vitamin deficiencies (vitamins A, D, E and K2, all largely from animal foods that also supply fatty acids for gut absorption) may partly account for high rates of NCD worldwide, especially in developing countries. Literature review based and GBD raw data based approaches should be complementary in assessing dietary and other attributable risks for NCD and other individual health outcomes.

Funding

None

Research in context

Evidence before this study

The Global Burden of Diseases, Injuries, and Risk Factors Study (GBD 2019) provides the most recent assessment of deaths, attributable to metabolic, environmental and occupational, and behavioural risk factors. Controversies abound in the field of nutritional epidemiology. The lipid hypothesis that dietary saturated fat and cholesterol promote cardiovascular diseases has been disputed with no scientific consensus on the outcome.

Added value of this study

This study assesses the evidence basis of deaths attributed to dietary risks and metabolic risk factors derived from systematic reviews of the medical literature in GBD 2019. This study uses GBD raw data formatted and population weighted to assess the worldwide deaths from noncommunicable diseases attributable to dietary and metabolic risk factors. With this GBD data analysis methodology, the levels of 20 dietary risk factors are assessed in cohorts with the highest and lowest rates of noncommunicable disease deaths. Worldwide GBD data show that many deaths are associated with low levels of animal foods and saturated fatty acids (kcal/day percapita) and associated with low levels of metabolic risk factors. These findings are at variance with the lipid hypothesis operating uniformly worldwide. In the UK, USA, Mexico, and Japan, with subnational GBD data, many deaths are attributable to high levels of animal foods, saturated fatty acids, and metabolic risk factors, supporting the lipid hypothesis.

Implications of all the available evidence

The findings of systematic literature reviews in assessing the health impacts of high metabolic risk factors are superior than using GBD data analysis because GBD data only assess mean cohort levels of metabolic risk factors. However, GBD data can show effects of dietary risk factors acting directly and mediating metabolic risks leading to noncommunicable disease deaths. This GBD data based methodology can enhance understanding of the complex interrelationships of diet, metabolic risk factors and noncommunicable disease deaths. The findings are consistent with a “fat soluble vitamin hypothesis” that deficiencies of vitamins A, D, E, and K2 and fatty acids from inadequate animal food consumption lead to increased cardiovascular disease and noncommunicable disease deaths.