Monday February 10 2014
Strokes usually affect older women
“Women have a poorer quality of life after stroke than men,” reports BBC News.
This headline stemmed from a new US study that found women had a lower quality of life than men three and 12 months after experiencing a stroke or mini-stroke.
Quality of life was assessed using a questionnaire known as the EQ-5D quality of life questionnaire, which “scores” quality of life based on certain factors such as mobility levels, how able a person is to take part in everyday activities and symptoms of depression, anxiety and pain. It then produces a score ranging from 1 (perfect health) to 0 (the worst health you could imagine).
While the results were statistically significant, the relative differences appeared small. For example at three months the average difference in quality of life score between men and women was just 0.036 points. And the quality of life difference between men and women at 12 months was even smaller, at 0.022 points.
Whether these differences are clinically important, or whether recovering stoke patients would see them as important needs consideration.
It’s worth noting that a lot of data was missing in this study, meaning many eligible people were excluded from the final data analysis. This may have biased the findings and will have made them less representative of all people recovering from stroke. Finally, the study was in the US which has a vastly different healthcare system than England. For better or for worse, the results in English residents may be different to those in the US.
In summary, this study provides tentative evidence that there may be a gender difference in quality of life post stroke in this group of US adults.
Where did the story come from?
The study was carried out by researchers from Wake Forest Baptist Medical Center, North Carolina (US) and was funded by Bristol-Myers Squibb/Sanofi Joint Partnership and the Agency for Healthcare Research and Quality.
The study was published in the peer-reviewed medical journal the American Academy of Neurology.
Many of the study contributors, including the main author, declared financial conflicts of interests related to financial links with pharmaceutical companies that manufacture stroke related drugs and other funding agencies. It is not clear if or how these conflicts of interest influenced the conduct and conclusions of this study.
The BBC’s coverage was factually accurate but neglected to mention the potential financial conflicts of interest underlying the research, the numerous limitations of the study, or discuss the importance of the relatively small quality of life differences found between men and women.
What kind of research was this?
This was a longitudinal analysis of information already collected as part of an on-going stroke registry in the US.
The researchers compared the quality of life of men and women three and 12 months after they had had a stroke or a mini-stroke (a transient ischaemic attack or TIA). They wanted to see if any gender related quality of life differences changed over time and whether demographic, socioeconomic and stroke specific factors impacted on post-stroke quality of life.
What did the research involve?
The study looked for gender differences in the quality of life of men and women three and 12 months after they had left hospital after being originally admitted with a diagnosis of stroke or mini-stroke.
Quality of life was measured using a validated EQ-5D quality of life questionnaire administered over the phone. Other medical and demographic background information was obtained from a national stroke database called The Adherence eValuation After Ischemic stroke–Longitudinal (AVAIL) Registry.
EQ-5D assesses quality of life using a formula measuring mobility, self-care, everyday activities, depression/anxiety and pain. It results in a score ranging from 1 (perfect health) to 0 (a theoretical health status equivalent to death).
The main analysis compared quality of life between the genders at three and 12 months. Further analysis took account of the potential influences of sociodemographic, clinical and stroke related factors.
What were the basic results?
From a group of 2,880 adults enrolled in the study only 1,370 were included in the final analysis. Missing data was the most common reason for excluding people from the final analysis. In the analysed group 53.7% were male and the median age was 65 years.
Underlying differences between men and women at the start of the study
Women were older than men, less likely to be married, less likely to have college-level education, more likely to be living alone, and more likely to not be working (by choice). Men were more likely to have a history of coronary heart disease, prior myocardial infarction (heart attack) and dyslipidemia (high levels of lipids such as cholesterol in the blood), and women were more likely to have had a mini-stroke. A higher proportion of women had greater disability at three months, and more severe depression.
Relative versus absolute differences
The absolute quality of life scores in the unadjusted analysis (at three months) showed men rated their quality of life marginally higher than women with a median score of 0.84 (interquartile range 0.76 to 1.00) versus 0.81 in women (interquartile range 0.71 to 0.85). At 12 months the score was the same for men 0.84 (interquartile range 0.76 to 1.00) but slightly improved in women 0.83 (interquartile range 0.71 to 1.00).
Gender differences in quality of life at three and 12 months
After adjustment for sociodemographic, clinical, and stroke-related factors, women had a statistically significant lower quality of life than men at three months. The average difference was 0.039 points on the EQ-5D score. The same was found at 12 months, although the average difference was smaller, at 0.022 points. The researchers reported that women fared worse in the dimensions of mobility, pain or discomfort, and anxiety or depression at three and 12 months. They found that many related factors significantly reduced the link between gender and quality of life: at three months the largest influencers were age, race and marital status.
How did the researchers interpret the results?
The researchers concluded that, “women have worse quality of life than men up to 12 months after stroke, even after adjusting for important sociodemographic variables, stroke severity, and disability”.
The study suggests that women have a lower quality of life than men three and 12 months after they have been discharged from hospital after experiencing a stroke or mini-stroke.
While the results were statistically significant, the relative differences appeared small. For example at three months (where the largest difference was found) the average difference in quality of life score between men and women was 0.036 points. This is on a quality of life scale that ranges from 0 (death) to 1 (perfect health). The quality of life difference at 12 months was 0.022 points. Whether these small differences are clinically important, or whether they would be perceived as important to recovering stoke patients needs consideration.
This study had a lot of missing data and this may have biased the findings and will have made them less representative of the general population of people recovering from stroke.
Furthermore, the link between gender and post stroke quality of life was heavily influenced by age, race and marital status (confounders). This raises the possibility that other confounders are still accounting for some or all of the proposed gender-quality of life link. While efforts were made to account for many confounders in the analysis, this may not have been comprehensive. This study weakness is common and is known as “residual confounding”.
Finally, the study involved US residents who may experience different treatment and post treatment care than English residents as the two countries have different healthcare systems. Consequently, the results might have been different if the study took place in England.
In summary, this study provides tentative evidence that there may be a gender difference in quality of life post stroke in this group of US adults. However, the difference found appeared small, and may be explained by residual confounding.
Analysis by Bazian. Edited by NHS Choices.
Follow Behind the Headlines on Twitter.
Join the Healthy Evidence forum.