Top five observational studies of 2018

January 2 2019 by , medical review by 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 study

Dairy 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 studies

In 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

Top five medical journal articles of 2018

Top five low-carb studies of 2018

Name

Provider / Domain

Expiration

Description

ckdc-premium

.dietdoctor.com

1 month

app-banner

.dietdoctor.dev.dietdoctor.com

1 day

This cookie shows whether user closed the App Banner prompt

_gaexp

Google LLC

dietdoctor.com

1 year

Used to determine a user's inclusion in an experiment and the expiry of experiments a user has been included in.

_gaexp

Google LLC

.dietdoctor.com

1 year

Used to determine a user's inclusion in an experiment and the expiry of experiments a user has been included in.

_opt_awcid

.dietdoctor.com

3 days

_opt_awmid

.dietdoctor.com

3 days

_opt_awgid

.dietdoctor.com

3 days

_opt_awkid

.dietdoctor.com

3 days

_opt_utmc

.dietdoctor.com

3 days

_opt_expid

.dietdoctor.com

25 seconds

gtm_auth

.dietdoctor.com

3 days

gtm_debug

.dietdoctor.com

3 days

gtm_experiment

.dietdoctor.com

3 days

gtm_preview

.dietdoctor.com

3 days

_hjAbsoluteSessionInProgress

Hotjar Ltd

.dietdoctor.com

30 minutes

The cookie is set so Hotjar can track the beginning of the user's journey for a total session count. It does not contain any identifiable information.

_ga

Google LLC

.dietdoctor.com

2 years

This cookie name is associated with Google Universal Analytics - which is a significant update to Google's more commonly used analytics service. This cookie is used to distinguish unique users by assigning a randomly generated number as a client identifier. It is included in each page request in a site and used to calculate visitor, session and campaign data for the sites analytics reports.

_dc_gtm_UA-3268327-1

.dietdoctor.com

1 minute

This cookie is associated with sites using Google Tag Manager to load other scripts and code into a page. Where it is used it may be regarded as Strictly Necessary as without it, other scripts may not function correctly. The end of the name is a unique number which is also an identifier for an associated Google Analytics account.

_hjFirstSeen

Hotjar Ltd

.dietdoctor.com

30 minutes

The cookie is set so Hotjar can track the beginning of the user's journey for a total session count. It does not contain any identifiable information.

_dc_gtm_UA-22012422-2

.dietdoctor.com

1 minute

AWSELBCORS

Amazon.com Inc.

www.podbean.com

5 minutes

The cookies AWSELB and AWSELBCORS are functionally the same cookies. The latter has an explicit SameSite attribute set because of changes made from Chrome 80 and upwards.

_ga_YMCP8KW9S4

.dietdoctor.com

2 years

_hjIncludedInSessionSample

Hotjar Ltd

www.dietdoctor.com

2 minutes

This cookie is set to let Hotjar know whether that visitor is included in the data sampling defined by your site's daily session limit

__cf_bm

Cloudflare Inc.

.vimeo.com

30 minutes

This cookie is used to distinguish between humans and bots. This is beneficial for the website, in order to make valid reports on the use of their website.

_gid

Google LLC

.dietdoctor.com

1 day

This cookie is set by Google Analytics. It stores and update a unique value for each page visited and is used to count and track pageviews.

CookieScriptConsent

CookieScript

www.dietdoctor.com

1 year

This cookie is used by Cookie-Script.com service to remember visitor cookie consent preferences. It is necessary for Cookie-Script.com cookie banner to work properly.

__cf_bm

Cloudflare Inc.

.podbean.com

30 minutes

This cookie is used to distinguish between humans and bots. This is beneficial for the website, in order to make valid reports on the use of their website.

_hjIncludedInPageviewSample

Hotjar Ltd

www.dietdoctor.com

2 minutes

This cookie is set to let Hotjar know whether that visitor is included in the data sampling defined by your site's pageview limit.

_dc_gtm_UA-22012422-1

.dietdoctor.com

1 minute

_gaexp_rc

.dietdoctor.com

25 seconds

Name

Provider / Domain

Expiration

Description

IDE

Google LLC

.doubleclick.net

1 year

This cookie is set by Doubleclick and carries out information about how the end user uses the website and any advertising that the end user may have seen before visiting the said website.

_uetvid

Microsoft Corporation

.dietdoctor.com

1 year

This is a cookie utilised by Microsoft Bing Ads and is a tracking cookie. It allows us to engage with a user that has previously visited our website.

loc

Oracle Corporation

.addthis.com

1 year 1 month

Stores the visitors geolocation to record location of sharer

test_cookie

Google LLC

.doubleclick.net

15 minutes

This cookie is set by DoubleClick (which is owned by Google) to determine if the website visitor's browser supports cookies.

_gcl_au

Google LLC

.dietdoctor.com

3 months

Used by Google AdSense for experimenting with advertisement efficiency across websites using their services

_uetsid

Microsoft Corporation

.dietdoctor.com

1 day

This cookie is used by Bing to determine what ads should be shown that may be relevant to the end user perusing the site.

uvc

Oracle Corporation

.addthis.com

1 year 1 month

Tracks how often a user interacts with AddThis

YSC

Google LLC

.youtube.com

Session

This cookie is set by YouTube to track views of embedded videos.

MUID

Microsoft Corporation

.bing.com

1 year

This cookie is widely used my Microsoft as a unique user identifier. It can be set by embedded microsoft scripts. Widely believed to sync across many different Microsoft domains, allowing user tracking.

_fbp

Meta Platform Inc.

.dietdoctor.com

3 months

Used by Facebook to deliver a series of advertisement products such as real time bidding from third party advertisers

VISITOR_INFO1_LIVE

Google LLC

.youtube.com

6 months

This cookie is set by Youtube to keep track of user preferences for Youtube videos embedded in sites;it can also determine whether the website visitor is using the new or old version of the Youtube interface.

Name

Provider / Domain

Expiration

Description

_ga_7S1SXKKDKN

.dietdoctor.com

2 years

Name

Provider / Domain

Expiration

Description

_hjSession_1945121

.dietdoctor.com

30 minutes

_hjSessionUser_1945121

.dietdoctor.com

1 year

_ga_Y4DLH4EPXM

.dietdoctor.com

2 years