The purpose of this study is to assess the effects of lifestyle risk factors on the risk of hospitalization for sciatica and to determine whether overweight or obesity modifies the effect of leisure-time physical activity on hospitalization for sciatica.
Methods
We included 4 Finnish prospective cohort studies (Health 2000 Survey, Mobile Clinic Survey, Helsinki Health Study, and Young Finns Study) consisting of 34,589 participants and 1259 hospitalizations for sciatica during 12 to 30 years of follow-up. Sciatica was based on hospital discharge register data. We conducted a random-effects individual participant data meta-analysis.
Results
After adjustment for confounding factors, current smoking at baseline increased the risk of subsequent hospitalization for sciatica by 33% (95% confidence interval [CI], 13%-56%), whereas past smokers were no longer at increased risk. Obesity defined by body mass index increased the risk of hospitalization for sciatica by 36% (95% CI 7%-74%), and abdominal obesity defined by waist circumference increased the risk by 41% (95% CI 3%-93%). Walking or cycling to work reduced the risk of hospitalization for sciatica by 33% (95% CI 4%-53%), and the effect was independent of body weight and other leisure activities, while other types of leisure activities did not have a statistically significant effect.
Conclusions
Smoking and obesity increase the risk of hospitalization for sciatica, whereas walking or cycling to work protects against hospitalization for sciatica. Walking and cycling can be recommended for the prevention of sciatica in the general population.
Introduction
Sciatica involves pain that radiates from the lower back along the sciatic nerve to the back of the thigh and down the leg, and is accompanied by clinical findings suggestive of compression or irritation of the lumbosacral nerve root.1, 2 A herniated lumbar disc with nerve root compression is the most common cause of sciatica.1, 2 The prevalence of clinically verified sciatica in the general population ranges between 2% and 5%.3, 4, 5 Sciatica is a more persistent and disabling condition than other low back syndromes.6 The majority of sciatica cases are, however, treated conservatively, and only a small proportion of the cases eventually need surgery.1, 2, 7 In general, sciatica is a relatively uncommon cause for hospitalization.8, 9, 10 Among metal industry workers, 4.4% of men and 5.9% of women had been hospitalized for cervical, thoracic, or lumbar intervertebral disc disorder during a 27-year follow-up.8 Moreover, among male construction workers, 0.8% had been hospitalized for lumbar disc disease during a 16-year follow-up,10 and among men working in private or public companies, 1.7% had been hospitalized for a herniated lumbar disc during a 33-year period.9
The etiology of sciatica is multifactorial.1 Of lifestyle risk factors, overweight and obesity,11 and smoking12increase the risk of sciatica, but the role of leisure-time physical activity in sciatica is uncertain.13 A meta-analysis11 showed that overweight increases the risk of clinically verified sciatica by 12% and hospitalization for sciatica by 16%. For obesity, the excess risk is 31% for sciatica and 38% for hospitalization due to sciatica. Moreover, another meta-analysis12 found that current smoking increases the risk of clinically verified sciatica by 35%, and hospitalization or surgery due to sciatica by 45%. Smoking cessation reduces the excess risk, and past smokers are 9%-10% more likely to have sciatica than never smokers.12 Furthermore, a recent meta-analysis of a limited number of prospective cohort studies found that a high level of leisure-time physical activity protects against lumbar radicular pain by 16%. Leisure-time physical activity had, however, no protective effect on clinically verified sciatica.13
Most of the previous studies on the role of lifestyle risk factors in clinically verified sciatica used a cross-sectional design, or were case control studies conducted among selected populations. The previous systematic reviews11,12, 13 identified only a limited number of prospective cohort studies on this topic. There may be reverse causation between leisure-time physical activity and sciatica. Individuals with lumbar radicular pain may limit their leisure activities because of fear of pain.14 Cross-sectional studies are more prone to reverse causation than prospective cohort studies. Moreover, there is a vicious cycle between obesity and physical inactivity.15 Physical inactivity contributes to weight gain, and decreased level of physical activity can be a consequence of obesity.15 A prospective cohort study found that physical inactivity increases the risk of lumbar radicular pain in abdominally obese individuals, but not in persons with normal waist circumference.16 It is unknown whether overweight or obesity modifies the effect of leisure-time physical activity on sciatica. The aim of this study was to investigate the effects of lifestyle risk factors on hospitalization for sciatica by conducting an individual participant data meta-analysis of 4 prospective cohort studies. Furthermore, we determined whether overweight or obesity modifies the effect of leisure-time physical activity on hospitalization for sciatica.
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-Rahman Shiri, MD, PhD, Ulla Euro, MD, Markku Heliövaara, MD, PhD, Mirja Hirvensalo, PhD, Kirsti Husgafvel-Pursiainen, PhD, Jaro Karppinen, MD, PhD, Jouni Lahti, PhD, Ossi Rahkonen, PhD, Olli T. Raitakari, MD, PhD, Svetlana Solovieva, PhD, Xiaolin Yang, PhD, Eira Viikari-Juntura, MD, PhD, Tea Lallukka, PhD
This article originally appeared in the December 2017 issue of The American Journal of Medicine.
