A claim you hear on longevity podcasts

Is a fasting blood sugar above 87 bad for your heart?

Leaning against. Of 7 studies that test it, 4 disagree, 2 partly agree and 1 agrees.

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The claim checked: Heart attack and stroke risk rises in a straight line once fasting blood sugar passes 87 Hear it at 6:42

What do the studies say?

Leaning against

Four of seven studies disagree. The biggest, a pooled analysis of 102 studies, found no clear link between fasting blood sugar and heart attacks or strokes anywhere in the normal range. A pooled analysis adds up the results of many smaller studies. In 11,092 American adults, a level of 100 to 126 mg per deciliter raised the risk of diabetes, not of heart disease or stroke. One Korean study agrees: there, risk rose from a level near 90 mg/dL. Two studies are mixed.

Computed from 7 studies that test this point, each judged by two readers, in full. 10 more studies are waiting for a full read and do not count yet.

The study behind the claim tested something else. See what it tested

What was said on the podcast?

“And they found that anything over 87, there was a really linear increase in your risk of heart attacks, strokes and so forth over that, above 87.”
Mark Hyman, The Doctor's Farmacy · Why Your Insulin Resistance Isn't Permanent (And How to Fix It) · 6:42 on YouTube
Episode check Heart risk climbs from a fasting blood sugar inside the normal range, the episode says. Four of seven studies disagree. 6 claims checked against 62 studies · 8 chapters not checked yet See the whole episode →
The study behind the claim The retelling misstates it

What did the study actually test?

On tape: a large Israeli study found that the risk of heart attacks and strokes rose in a linear way above a fasting glucose of 87. This is the only large Israeli study with the 87 mg/dL cut point, so Israel, size and the number match. The outcome does not match: the study measured only new type 2 diabetes in young men. It did not measure heart attacks or strokes. The paper mentions cardiovascular and stroke deaths only when it cites other studies of people aged 45 and over. The search found no Israeli study that reports heart attack or stroke risk rising from 87. The paper has an erratum (N Engl J Med 2006;354:2401) that was not read, so its content is not checked here. Normal fasting plasma glucose levels and type 2 diabetes in young men. N Engl J Med, 2005. Prospective cohort (MELANY study) of Israel Defense Forces men followed 1992 to 2004, mean follow-up 5.7 years; Cox models across quintiles of normal fasting glucose, 13,163 apparently healthy men aged 26 to 45 (mean 32) in Israeli army career service, all with fasting glucose below 100 mg/dL at baseline; no women.

What was saidWhat the study did
What was given Matches A fasting blood sugar above 87 Fasting plasma glucose in the third to fifth quintiles of the normal range (87 to 99 mg/dL)
Compared with Matches A fasting blood sugar of 87 or less The bottom quintile, below 81 mg/dL
What was measured Differs Heart attacks and strokes New type 2 diabetes
Who took part Differs Adults in general Israeli army men aged 26 to 45 with normal fasting glucose

What it found

“A multivariate model, adjusted for age, family history of diabetes, body-mass index, physical-activity level, smoking status, and serum triglyceride levels, revealed a progressively increased risk of type 2 diabetes in men with fasting plasma glucose levels of 87 mg per deciliter (4.83 mmol per liter) or more, as compared with those whose levels were in the bottom quintile (less than 81 mg per deciliter [4.5 mmol per liter], P for trend <0.001).”

PMID 16207847

How the authors extend it

“Higher fasting plasma glucose levels within the normoglycemic range constitute an independent risk factor for type 2 diabetes among young men, and such levels may help, along with body-mass index and triglyceride levels, to identify apparently healthy men at increased risk for diabetes.”

PMID 16207847

Supported by the Israel Defense Forces Medical Corps. The authors state they alone were responsible for design, analysis and writing, without censorship by the Israel Defense Forces. Two readers agreed on the label, and the paper was read in full.

The point checked Leaning against

In adults without diabetes, the risk of heart attacks and strokes rises linearly with fasting blood sugar above about 87 mg/dL

Agree 1

other primary study · 2013

“In a large cohort of Korean men and women, we found that fasting glucose level was associated with higher risk for major CVD outcomes, increasing from a level of ∼90 mg/dL after controlling for other risk factors.”

Fasting glucose level and the risk of incident atherosclerotic cardiovascular diseases. Diabetes Care
Who: Korean government employees, teachers and dependents aged 30-95 without reported CVD, liver disease, cancer, respiratory disease or diagnosed diabetes (Korean Cancer Prevention Study)
PMID 23404299

Partly agree 2

controlled trial · 2005

“The significant relationship between fasting plasma glucose and the primary outcome (but not the other outcomes) was retained after adjustment for the presence of diabetes (relative risk [RR]=1.06; 95% CI 1.00–1.12; p=0.043).”

The relationship between dysglycaemia and cardiovascular and renal risk in diabetic and non-diabetic participants in the HOPE study: a prospective epidemiological analysis. Diabetologia
Who: high-risk HOPE trial participants enrolled in Canada (fasting glucose subset), diabetic and non-diabetic combined
PMID 16059716

pooled analysis · 2016 · landmark

“Importantly, we observed increased risks when fasting plasma glucose was as low as 5.6 mmol/L according to the current ADA definition of impaired fasting glucose (IFG-ADA).”

Association between prediabetes and risk of cardiovascular disease and all cause mortality: systematic review and meta-analysis. BMJ
Who: prospective general-population cohorts of adults aged ≥18 comparing prediabetes with normoglycaemia
PMID 27881363

Disagree 4

pooled analysis · 2010 · landmark

“Furthermore, there were no material associations with vascular risk at fasting blood glucose concentrations between 3·9 mmol/L and 5·6 mmol/L.”

Diabetes mellitus, fasting blood glucose concentration, and risk of vascular disease: a collaborative meta-analysis of 102 prospective studies. Lancet
Who: individual records from 102 prospective studies of adults without initial vascular disease (mean age 52, 43% women, 96% Europe/North America/Australasia)
PMID 20609967

pooled analysis · 2010

“In analyses across tenths of fasting glucose values, adjusted HRs for CHD were generally weak and nonsignificant at levels below 7 mmol/l ( Figure 1 ).”

Markers of dysglycaemia and risk of coronary heart disease in people without diabetes: Reykjavik prospective study and systematic review. PLoS Med
Who: Reykjavik cohort (Icelandic adults without history of MI) plus 26 Western prospective cohorts of people without diabetes
PMID 20520805

controlled trial · 2010

“Elevations in FPG in the non-diabetic range were not associated with long-term risk of cardiovascular events in middle-aged men in WOSCOPS.”

Fasting plasma glucose in non-diabetic participants and the risk for incident cardiovascular events, diabetes, and mortality: results from WOSCOPS 15-year follow-up. Eur Heart J
Who: 6447 moderately hypercholesterolaemic Scottish men (mean age 55) with no history of CVD or diabetes and fasting glucose <7.0 mmol/L (WOSCOPS)
PMID 20395260

trial or observed group · 2010 · landmark

“As compared with a baseline fasting glucose level of less than 100 mg per deciliter, a level of 100 to less than 126 mg per deciliter was associated with diagnosed diabetes (hazard ratio, 2.31; 95% CI, 2.06 to 2.59) but not with coronary heart disease (hazard ratio, 1.03; 95% CI, 0.91 to 1.18), ischemic stroke (hazard ratio, 0.97; 95% CI, 0.76 to 1.23), and death from any cause (hazard ratio, 1.07; 95% CI, 0.96 to 1.21) after adjustment for covariates (model 2b) (Table 3), whereas undiagnosed diabetes (defined as a fasting glucose level of 126 mg per deciliter or higher at baseline) was significantly, independently associated with the development of coronary heart disease (hazard ratio, 1.29; 95% CI, 1.04 to 1.61), ischemic stroke (hazard ratio, 1.89; 95% CI, 1.33 to 2.69), and death from any cause (hazard ratio, 1.31; 95% CI, 1.07 to 1.61).”

Glycated hemoglobin, diabetes, and cardiovascular risk in nondiabetic adults. N Engl J Med
Who: 11,092 black or white middle-aged adults in the ARIC study without a history of diabetes or cardiovascular disease
PMID 20200384

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