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March 22, 2010

Lonely people are more likely to develop high blood pressure

Lonely people are more likely to develop high blood pressure later in life, the new report saying that chronic feelings of loneliness push up blood pressure over time.
LonelinessThis news story is based on research in 229 participants in the US. The researchers used a complex statistical model to look at whether reported feelings of loneliness could predict blood pressure over time.

Though this study did find an association between blood pressure & loneliness, it was a relatively small effect. At the end of the study four years later, there was only a small difference in predicted blood pressure between people who were lonely & those who weren’t (about 2mmHg). Raised blood pressure is associated with an increased risk of stroke, heart attack, kidney problems & dementia. However, for most people, it is difficult to say what, if any, health-related effect this small relative increase would have.

Where did the story come from?

This research was carried out by Dr Louise C. Hawkley & colleagues from the University of Chicago. The study was funded by the National Institute of Aging & the John Templeton Foundation. The paper was published in the (peer-reviewed) medical journal Psychology & Aging.
However, it does not state that the researchers do not list the absolute blood pressure readings of the participants, only the differences between lonely & non-lonely people. It is not clear whether the lonely people’s blood pressure was in a clinically high category & presented an actual risk. Furthermore, the increase in blood pressure was quite small, & some indication of just how clinically significant this was would 've been useful.

What kind of research was this?

This cohort study followed a group of participants over four years to see whether there was an association between their self-reported loneliness & their blood pressure over this period.
The researchers say that previous cross-sectional studies 've investigated whether loneliness is associated with health problems. However, as this type of study only looks at a group of people at one point in time, it is not possible to say that one thing has directly caused the other. The researchers suggested that possible effects of loneliness may accumulate over time & they wanted to test whether this was the case.

Loneliness was defined as a “distressing feeling that accompanies discrepancies between one’s desired and actual social relationships” & the study said that although some individuals who are socially isolated may feel lonely, the feeling of loneliness is more associated with an individual’s perception of their situation.

What did the research involve?

The researchers used data collected between 2002 & 2006 from a longitudinal population-based study of non-Hispanic white, black & non-black Hispanic people born between 1935 & 1952. All participants were from Cook County Illinois, USA.

There were 229 participants, ranging in age from 50 to 68. Participants visited the researchers’ laboratory once a year for the duration of the study. At these visits, researchers carried out standard psychological surveys, health & medical interviews, body measurements & cardiovascular measurements including systolic blood pressure. Participants were also asked to bring any medications they were taking so that the drugs’ names, dosage & frequency the drug was taken could be recorded.

To rate the participants’ loneliness & their satisfaction with their social network, a scale called the UCLA loneliness Scale-Revised (UCLA-R) was used, asking individuals to rate how much their own personal feelings were represented by statements such as, “I lack companionship” & “I feel in tune with the people around me.”

The participants’ social network was also classified according to their marital status, how many relatives & friends they interacted with at least once every two weeks, voluntary group membership & religious group affiliation. Social networks were categorised as being low, medium, medium-high and high.

Information on other lifestyle factors that can affect health were also collected, including smoking status, alcohol intake & the amount of exercise they did.

The statistical analysis was aimed at testing whether there were short & long-term associations between loneliness & blood pressure. The researchers tested whether changes in loneliness over one year predicted changes in blood pressure the following year, & also the degree to which the initial loneliness measurement explained changes in blood pressure over a two, three & four-year period. The data was analysed using a cross-lagged panel model, which is a type of statistical analysis that can measure two or more variables at several points in time.

What were the basic results?

The researchers found that the participants’ blood pressure was not predicted by their feelings of loneliness the year before (probability (p) = 0.3). However, loneliness at the start of the study did predict increases in blood pressure two, three, & four years later (p <0.05). The cross-lagged panel model predicted that if two individuals had a difference in loneliness score of 10 at baseline (study start), five years later the lonelier person’s blood pressure would be 2.1mmHg higher. However, when the model was adjusted to take into account the fact that lonely people were also more likely to have higher blood pressure at baseline, it predicted that five years later lonelier peoples’ blood pressure was 2.3mmHg higher than that of less lonely people. The effect of loneliness on blood pressure was independent of age, gender, ethnicity, cardiovascular risk factors, medications, health conditions & the effects of depressive symptoms, social support, perceived stress & hostility.


How did the researchers interpret the results?
Moreover, independent of social network size, age, gender, race or ethnicity, traditional cardiovascular risk factors (BMI, poor health behaviors), cardiovascular medications, chronic health conditions, & a set of related psychosocial variables (depressive symptoms, perceived stress, social support, hostility), loneliness appears to be a unique risk factor for elevated [blood pressure] & increases in [blood pressure] over time.

Conclusion

This study used complex statistical modelling with data from a cohort study to suggest that there is a long-term association between loneliness & blood pressure. Though these differences in blood pressure were small, they were statistically significant. There are a number of aspects to the study that should be taken into account when interpreting these observations:

  • The age range of the population sample was 50 to 68. Older individuals may be more likely than younger people to 've age-related changes to their cardiovascular system or to be on medications that can affect blood pressure. As such, the study cannot ascertain the effects of loneliness on younger individuals.
  • The study was relatively small & the researchers made a large number of statistical comparisons & adjustments. This increases the likelihood that the observations may be down to chance.
  • The participants were from one region of the US, where typical lifestyles or the sociological environment may differ from individuals in the UK. In the US people require health insurance to receive medical treatment. The researchers suggest that there may be an association between loneliness & a lower probability of having health insurance, which may lead to differences in the healthcare that individuals receive for any cardiovascular problems. If this was the case then this is likely to have led to an exaggeration of differences between lonely & non-lonely individuals in this study.
  • The researchers did not state the absolute blood pressure readings of the participants, only the differences between lonely & non-lonely people. It is not clear whether the lonely people’s blood pressure was in a clinically high category & presented an actual risk.

Though this study did find an association between blood pressure & loneliness, it was a relatively small effect. At the end of the study four years later, there was only a small difference in predicted blood pressure between people who were lonely & those who weren’t (about 2mmHg). Raised blood pressure is associated with an increased risk of stroke, heart attack, kidney problems & dementia. However, for most people, it is difficult to say what, if any, health-related effect this small relative increase would have.

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