Does losing your job up the risk of a heart attack?

'Losing your job can be deadly, because it increases the risk of having a heart attack by up to two-thirds,' The Daily Telegraph reports.

The news is based on a US study that examined the association between different aspects of unemployment (such as number of job losses and time spent out of work) and the risk of having a heart attack.

The researchers followed 13,451 older American adults for a period of up to 18 years and found that unemployment status, multiple job losses and short periods without work are all significant risk factors for a heart attack, even with adjustment for conventional risk factors such as smoking.

Despite the authors' findings, there are several limitations to this study:

• heart attacks were self-reported and not verified by medical records
• this was a US study, so there may be economic and social factors that may not be applicable to the UK population, such as the fact that Americans have to pay for their healthcare
• people who took part in the study were older adults – arguably the last generation who grew up with the concept that a job would be for life – and younger adults better adapted to a world of job insecurity would possibly not react in the same way

Of note, the reason for job loss was not explored by the researchers. This could potentially have provided more meaningful results, as it may have revealed other possible confounding factors that could be involved in the link between job loss and heart attack risk.

However, the study does seem to suggest there is a link between job and economic insecurity and ill heakth.

Where did the story come from?

The study was carried out by researchers from Duke University in the US and was funded by the National Institute on Aging and the Social Security Administration. It was published in the peer-reviewed journal Archives of Internal Medicine.

Once past the attention-grabbing media headlines, the story is covered appropriately by the papers, although none of them report that the reasons for 'job loss' were not investigated by the study.

What kind of research was this?

This was a prospective cohort study looking at the associations between different aspects of unemployment and the risks of heart attack (acute myocardial infarctions, or AMI) among adults in the US.

While previous research has examined the association between employment status and AMIs, as well as other types of diseases, little is known about the cumulative effect of multiple job losses and unemployment on the risk of heart attack. This was a question the researchers tried to address in this study.

The researchers say that information about employment status and the risk of heart attack could improve our ability to screen individuals with a high risk of having a heart attack.

What did the research involve?

The researchers used data from the US Health and Retirement Study (HRS). The HRS comprises a nationally representative sample of adults over the age of 50 who were followed up by the researchers every two years from 1992 to 2010. 

The sample used by the researchers included 13,451 participants aged 50 to 75 years, 9,824 of whom were from the original HRS cohort (people born between 1931 and 1941).

The remaining participants were made up of two age groups added to supplement the HRS cohort:

• people born between 1942 and 1947 (the 'war cohort')
• people born between 1948 and 1953 (the 'early baby boomer cohort')

The researchers collected information on the participants' past employment histories (number of jobs, job losses, and so on) at the start of the study.

Every two years the researchers carried out follow-up interviews to ask the participants about:

• employment status (employed or unemployed, excluding retirement)
• cumulative number of job losses (0, 1, 2, 3, or more than 4)
• cumulative time unemployed (0 years, more than 0-1 year, 2-4 years, more than 5 years)

All employment information was self-reported by the participants and the researchers considered participants who reported themselves as 'not employed' and 'not retired' as unemployed.

At each interview participants were also asked whether or not they had a heart attack or myocardial infarction in the past two years, and if so when it had occurred.

The researchers made adjustments for a number of confounders known to be associated with an increased risk of a heart attack:

• socioeconomic factors such as education and income
• behavioural factors such as smoking status, alcohol use and physical activity
• psychological factors such as depressive symptoms
• clinical factors such as body mass index, cholesterol, diabetes and high blood pressure

They also examined the association between job instability and heart attack risk by sex and race or ethnicity.

What were the basic results?

A total of 1,061 acute myocardial infarction events were reported during the study period (7.9% of all participants). Following adjustments, the main results of this study were:

• the risk of heart attack was significantly higher among participants who reported being unemployed (hazard ratio 1.35, 95% confidence interval [CI] 1.10 to 1.66)
• compared with no job loss, the risk of heart attack grew with an increasing number of job losses – for example, with one job loss the hazard ratio was 1.22, 95% CI 1.04 to 1.42, compared with four or more cumulative job losses, where the hazard ratio was 1.63, 95% CI 1.29 to 2.07
• the risk of heart attack was significantly higher within the first year of unemployment (hazard ratio 1.27, 95% CI 1.01 to 1.60) but was not found to be significant for longer periods of unemployment
• retirement was not associated with an increased risk of heart attack

The researchers found that the adjusted findings were comparable to other major risk factors for heart attack, such as:

• smoking (hazard ratio 1.44, 95% CI 1.24 to 1.69)
• diabetes (hazard ratio 1.51, 95% CI 1.30 to 1.75)
• high blood pressure (hazard ratio 1.62, 95% CI 1.42 to 1.86)

How did the researchers interpret the results?

The researchers conclude that unemployment status, multiple job losses and short periods without work are all significant risk factors for acute cardiovascular events, or heart attacks. They say that the increased risks associated with multiple job losses were comparable to other traditional risk factors for heart attack such as smoking, diabetes and high blood pressure.

One of the researchers, Dr Linda George, is quoted in the media as saying that, "We think it is the stress of dealing with unemployment that may explain this. And, probably, job loss has a stronger effect than a stressful job".

Conclusion

Overall, this study provides some evidence of an association between unemployment and the risk of a heart attack. Importantly, there are some limitations to this study which may restrict the findings. These include:

• Employment status and heart attack events were self-reported by participants. It is possible that participants did not accurately report these events, which makes the results less reliable. Self-reported data validated by medical records would have provided more accurate information.
• The researchers report that no data was available for certain clinical factors such as the treatment and control of high blood pressure and diabetes, as well as other preventative measures taken to reduce the likelihood of a heart attack. This information would have made the results more robust.
• The researchers also report that job characteristics – such as whether the job was office-based or manual work – were not recorded, including the reasons for job loss. This would have provided more information on the type of job loss, for example whether it was the end of a contract, a redundancy or a voluntary choice other than retirement.
• Interestingly, the researchers considered participants who reported not being employed or retired as unemployed. This does not take into account participants who may have gone back to study for a period of time or who worked on a short-term contract basis. 

It is important to note that this research does not prove that there is a direct cause-and-effect link that unemployment leads to heart attack – it can only say that there is an association.

The authors report further research in this area should consider the influence of other job-related factors such as seasonal employment, under-employment, multiple jobs, family demands and the timing of job loss.