Higher Heart Rate, BP in Teens Early Marker of Mental Illness?

Pauline Anderson

October 28, 2016

An elevated resting heart rate (RHR) and high blood pressure (BP) in male adolescents are linked to an increased risk for certain psychiatric disorders, particularly obsessive compulsive disorder (OCD), later in life, new research suggests.

The study, conducted by investigators at the University of Helsinki, Finland, and the Karolinska Institute, Stockholm, Sweden, also showed that lower RHR and BP were associated with subsequent diagnoses of substance abuse disorders (SUDs) and violent criminal behavior.

The results suggest that altered cardiac autosomal activity may represent an early marker of psychiatric disorders in men, said lead author Antti Latvala, PhD.

"This study provides new evidence for the role of autonomic nervous system functioning underlying some psychiatric disorders. Previous studies showed some autonomic abnormalities related to various psychiatric disorders, but none of them actually systematically studied several different disorders or looked at the predictive associations," Dr Latvala told Medscape Medical News.

Dr Antti Latvala

The study was published online October 26 in JAMA Psychiatry.

No Link to Depression

For the study, researchers used several Swedish national registers, including the Conscription Register. During a conscription assessment for the Swedish Armed Forces, which until 2010 was mandatory for men at age 18 years, RHR and BP were measured.

Valid RHR measurements were available for more than a million men, and valid systolic blood pressure (SBP) and diastolic blood pressure (DBP) measurements were available for about 1.5 million men.

For information on psychiatric disorders, researchers used the National Patient Register. They studied seven categories of major disorders: OCD, anxiety disorders, posttraumatic stress disorder, depressive disorders, bipolar disorder, schizophrenia, and substance use disorders (SUDs). They also looked at violent criminal convictions from the Swedish Crime Registry.

The median length of follow-up was 31.8 years.

After adjusting for birth year and conscription year, every 10-unit increase in RHR was associated with a 5% increased risk for depression (hazard ratio [HR], 1.05), an 8% increased risk for anxiety disorders, a 10% increased risk for schizophrenia, and an 18% increased risk for OCD.

The associations were somewhat weakened after adjusting for height, weight, body mass index, cognitive ability, parental immigrant status, childhood socioeconomic status, and cardiorespiratory fitness.

There were similar results for blood pressures. For example, a 10-unit increase in DBP was associated with a 6% elevated risk for anxiety (HR, 1.06) and an 11% increased risk for both OCD and schizophrenia in the fully adjusted model.

Investigators compared men in the highest category of RHR (>82 beats per minute) with those in the lowest RHR category (<62 beats per minute). In a model adjusted for all covariates as well as cardiorespiratory fitness, men in the highest RHR category had a 69% increased risk for OCD (HR, 1.69; 95% CI, 1.46 - 1.94), a 21% increased risk for schizophrenia (HR, 1.21; 95% CI, 1.11 - 1.33), and an 18% increased risk for anxiety (HR, 1.18; 95% CI, 1.13 - 1.22).

Similar associations were found after comparing highest and lowest BP measurements. Men with the highest DBP (>77 mmHg) had a 30% to 40% higher risk for OCD than men with the lowest DBP (<60 mmHg).

There were no clear associations between the measurements and depression.

Data for a Risk Score?

Why would the relationships be in general strongest for OCD? "OCD is typically a very severe disorder, and the clinical diagnosis might be more reliable compared to something like depression, which might be more heterogeneous," said Dr Latvala.

The risks for SUDs and antisocial behavior were predicted by lower RHR and systolic blood pressure, especially after adjusting for the confounding effect of physical fitness. For example, in the fully adjusted model, the HR for violent criminality for the lowest RHR group compared to the highest was 1.45 (95% CI, 1.40 - 1.49).

That elevations in RHR and blood pressure were associated with increased risk for some psychiatric illnesses but lower measurements were associated with risk for SUDs may seem counterintuitive, given the relationship between mental illness and substance use. It illustrates a "highly complex picture" of these associations, said Dr Latvala.

Although anxiety and depression may lead to substance use, "at the same time, there are other risk factors for substance use disorders, such as genetic factors," he said.

Researchers excluded men who had a psychiatric diagnosis before their testing, but it is possible that the elevated measurements were early signs of mental illness.

"We know that most of these disorders tend to have an early onset in life, and it's a very likely scenario that at least some proportion of these men were already having some symptoms during adolescence when the heart rate and blood pressure were measured," said Dr Latvala.

Dr Latvala stressed that he and his colleagues are not claiming a causal association.

"We are not saying that heart rate or blood pressure would causally increase the risk of these disorders. The more likely interpretation is that these physiological measures are perhaps indicators of some processes going on early on, and they are part of the risk for having these diagnoses later in life."

The results, he said, do not have direct clinical implications.

"First of all, although we did find the association ― it's there, and it's real ― it's still only a statistical association."

In addition, the association is not strong enough for clinicians to be able to "predict who will get OCD or anxiety or whatever," and the mechanism driving the association is not that well understood, he said.

Instead, this new information might be used in future as part of a risk score. "Perhaps elevated heart rate could be a small piece of that combination of different risk factors that might be useful for prediction."

Dr Latvala has disclosed no relevant financial relationships.

JAMA Psychiatry. Published online October 26, 2016. Full text

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