Adherence to Nordic-Style Diet Linked to Lower Risk for Total Stroke

Deborah Brauser

January 11, 2017

Consuming a Nordic-style diet — which includes cabbages, rye bread, fruit such as apples and pears, root vegetables, oatmeal, and fish — may be protective against some types of stroke, new research suggests.

In a cohort of more than 55,000 participants in the population-based Danish Diet, Cancer, and Health study, those with higher Healthy Nordic Food Index scores at baseline had a significantly lower risk for total stroke during an average follow-up of 14 years compared with those with lower index scores.

After adjustment for multiple confounders, total stroke risk was 14% lower for the high-adherence group.

Although a trend was also observed between Nordic diet adherence and ischemic stroke overall, it was not statistically significant. However, there was a significant inverse association for its subtype of large-artery atherosclerosis.

Still, lead author Camilla Plambeck Hansen, PhD, Department of Public Health at Aarbus University, Denmark, pointed out that more studies of these associations are needed before it can be recommended that clinicians propose a Nordic diet to their own patients at risk for stroke.

Dr Camilla Plambeck Hansen

Instead, "maybe they should just consider an alternative if patients have problems adapting to a Mediterranean diet," Dr Hansen told Medscape Medical News. "Other diets may be just as good."

The study results were published online January 3 in Stroke.

Poor Adherence to Mediterranean Diet

Although a Mediterranean-style diet includes fish, just as a Nordic diet does, it also emphasizes olive oil, legumes, and different types of fruits and vegetables.

As reported by Medscape Medical News, the Mediterranean diet has been associated with higher total brain volume, increased cortical thickness, better cognitive function, and reduced risk for stroke.

"However, adherence to a Mediterranean dietary pattern is still relatively poor in the Nordic countries, probably because of differences in cultural food preferences and food availability," write the investigators.

So they sought to examine effects from consuming a diet of food traditionally eaten in these countries to see whether that too could help prevent stroke.

The researchers examined data for 55,338 Denmark-born participants (52% women; mean age, 56.1 years) in the Diet, Cancer, and Health study.

All filled out a 192-item food-frequency questionnaire at baseline regarding their intake over the previous 12 months. The Healthy Nordic Food Index was then used to record Nordic dietary patterns.

"Root vegetables" included carrots and celery, and "cabbages" included broccoli, cauliflower, kale, brussels sprouts, and white and red cabbage. An Index score of 4 to 6 signified high adherence to a Nordic diet and a score of 0 to 1 signified low adherence.

After a mean of 13.5 years of follow-up, there were 2283 cases of stroke reported. Of these, 82.3% were ischemic strokes, 17.1% were hemorrhagic strokes, and 0.6% were considered to be "unspecified" strokes.

Among the ischemic strokes, the most common subtypes were small-artery occlusions (n = 844), stroke of underdetermined cause (n = 516), and large-artery atherosclerosis (n = 319). Among the participants who had hemorrhagic strokes, 274 had an intracerebral hemorrhage and 117 had a subarachnoid hemorrhage.

Inverse Associations

The incidence rate per 10,000 person-years for total stroke was 27.3 for the high adherers to the Nordic diet compared with 39.5 for the low adherers.

After adjustment for total energy and alcohol intake, smoking, physical activity, and education, the hazard ratio (HR) for total stroke for the high vs low adherers was 0.86 (95% confidence interval [CI], 0.76 - 0.98; P = .02).

The same adjustment model also showed a trend for the overall category of ischemic stroke, but it was not significant (P = .07).

This inverse association "was mainly driven by a lower risk of stroke because of large-artery atherosclerosis," which was significant, note the investigators (HR, 0.68; 95% CI, 0.48 - 0.95; P = .03).

There were no significant associations or even trends between the Nordic diet and risk for total hemorrhagic stroke, although an inverse trend was observed for intracerebral hemorrhage.

When asked whether the investigators also looked at individual food items in the Nordic diet, such as fish or apples, Dr Hansen said they did. "And in general, all the components were inversely associated with stroke." However, she noted that this was part of supplementary analysis.

"In conclusion, adherence to a healthy Nordic diet was associated with lower risk of stroke in this large Danish cohort study of men and women," write the researchers.

But are these findings generalizable to other populations? "That's hard to say," answered Dr Hansen, noting that a past study in Swedish women didn't see any association between overall stroke and this type of diet.

"So we need studies in other populations to see if our findings can be applied to other cohorts or not."

She added that because adherence to the Mediterranean diet may not be high for individuals living in different parts of the world, "it might be easier to convince [them] that they need to eat more rye bread than to tell them they should eat olive oil or fruits that are not very traditional in Nordic countries."

"If a certain diet is too difficult for people to adapt to, we need to come up with something else," said Dr Hansen.

Healthy Behaviors Beyond Diet "Key"

Invited to comment, David S. Knopman, MD, professor of neurology at the Mayo Clinic, Rochester, Minnesota, told Medscape Medical News that he was impressed that the study included a large sample, with both men and women, and that it had a hard endpoint.

"They found that there was a benefit in terms of reduction in incident stroke in those who adhered to this Nordic diet, which is really quite a bit different than the Mediterranean diet," said Dr Knopman, who was not involved with this research.

However, there were the same limitations found in most observational studies, he added. And he would have liked to have seen effects from this type of diet on cognition.

Also, "the problem with most diet studies is that you see a lack of specificity in the outcomes," Dr Knopman noted, adding that diet is just one component of a healthy lifestyle.

"I think that the takeaway for clinicians is to be skeptical of reports about specific diets. It's appropriate to recommend reasonable diets and avoiding things that seem to be junk food. But adherence to healthy behaviors beyond diet is really the key message," he concluded.

The study was funded by the former Danish Council for Strategic Research, which is now the Innovation Fund Denmark, and by the Danish Cancer Society. The study authors and Dr Knopman have disclosed no relevant financial relationships.

Stroke. Published online January 3, 2017. Abstract

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