Top five observational studies of 2018
, medical review by Dr. Andreas Eenfeldt, MD
in Science & health 
Observational research is great for pointing out associations that merit further study — typically with randomized clinical trials — to determine if there is a causal relationship. In 2018, these observational studies caught our eye:
1. Could full-fat dairy help you live longer?
Otto de Oliveira et. al. in The American Journal of Clinical Nutrition:
Serial measures of circulating biomarkers of dairy fat and total and cause-specific mortality in older adults: the Cardiovascular Health Study
Long-term exposure to circulating… [fatty acids from dairy fat] was not significantly associated with total mortality or incident cardiovascular disease among older adults. High circulating heptadecanoic acid was inversely associated with cardiovascular disease and stroke mortality and potentially associated with higher risk of non-CVD death.
Read our take on this study in our post, “Could full-fat dairy products help you live longer?”
2. Does more insulin lead to obesity or is it the other way around?
Dr. Christina Astley et. al. in Clinical Chemistry
Genetic evidence that carbohydrate-stimulated insulin secretion leads to obesity
Mendelian randomization analyses provide evidence for a causal relationship of glucose-stimulated insulin secretion on body weight, consistent with the carbohydrate–insulin model of obesity.
Read our take on this study in our post, “New genetic study: Obesity may be caused by high insulin.”
3. Is high carbohydrate intake the best predictor of cardiovascular disease?
Pavel Grasgruber et. al. in Nutrients:
Global correlates of cardiovascular risk: A comparison of 158 countries
The indicators of cardiovascular diseases always show the most consistent association with high carbohydrate consumption, especially in the form of high-glycaemic cereals, in particular wheat. Other suspect variables are alcohol (mainly in its distilled form) and sunflower oil, but their roles are limited to Europe where their consumption rates are sufficiently high.
4. Does high blood sugar cause dementia?
Fanfan Zheng et. al in Diabetologia:
HbA1c, diabetes and cognitive decline: the English Longitudinal Study of Ageing
Significant longitudinal associations between HbA1c levels, diabetes status and long-term cognitive decline were observed in this study. Future studies are required to determine the effects of maintaining optimal glucose control on the rate of cognitive decline in people with diabetes.
5. Do high LDL cholesterol levels protect against dementia?
Fen Zhou et. al. in Frontiers in Neurology:
High low-density lipoprotein cholesterol inversely relates to dementia in community-dwelling older adults: The Shanghai Aging Study
Our data indicate that high level of LDL-C is inversely associated with dementia in older Chinese adults. High level of LDL-C may be considered as a potential protective factor against cognitive decline.
Read our take on this study in our post, “High LDL cholesterol might protect against dementia”
Honorable mention
Two additional dairy-fat studies and a retrospective analysis of existing data that attempts to establish a timeline for diabetes are also worth reading:
- Does dairy consumption help you live longer?
Mahshid Dehghan et. al. in The Lancet:
Association of dairy intake with cardiovascular disease and mortality in 21 countries from five continents (PURE): a prospective cohort studyDairy consumption was associated with lower risk of mortality and major cardiovascular disease events in a diverse multinational cohort.
- Can full-fat dairy protect you from type 2 diabetes?
Fumiaki Imamura in PLOS Medicine:
Fatty acid biomarkers of dairy-fat consumption and incidence of type 2 diabetes: A pooled analysis of prospective cohort studiesIn a large meta-analysis that pooled the findings from 16 prospective cohort studies, higher levels of 15:0, 17:0, and t16:1n-7 [all biomarkers of dairy-fat intake] were associated with a lower risk of type 2 diabetes.
Read our take on this study in our post, “Can cheese and butter protect against type 2 diabetes?“
- Are there signs of type 2 diabetes at least a decade before diagnosis?
Hiroyuki Sagesaka et. al. in Journal of the Endocrine Society:
Type 2 diabetes: When does it start?Fasting plasma glucose was significantly elevated in those who developed diabetes at least 10 years before diagnosis of diabetes, and this was also the case in those who developed prediabetes. Glucose dysregulation precedes diagnosis of diabetes at least for 20 years.
Read our take on this study in our post, “Risk of diabetes starts long before actual diagnosis.“
Every year, we see interesting associations in new observational studies. What findings will 2019 bring forward? Stay tuned!
Earlier
Top five opinion editorials of 2018