Study type: Epidemiological study (observational study)

Electric Blanket Use and Risk of Thyroid Cancer in the Women's Health Initiative Observational Cohort. epidem.

Published in: Women Health 2015; 55 (7): 829-841

Aim of study (acc. to author)

A cohort study was conducted in the USA to investigate the association between electric blanket use and thyroid cancer incidence in women.

Further details

The definition of electric blanket was inclusive of electric heating pad, electric mattress pad, and heated water bed in addition to blankets.

Endpoint/type of risk estimation

Type of risk estimation: (hazard ratio)



Exposure groups

Group Description
Group 1 ever electric blanket use: no
Group 2 ever electric blanket use: yes
Reference group 3 former/current use: never
Group 4 former/current use: former
Group 5 former/current use: current
Reference group 6 type of use: never
Group 7 type of use: warming up only
Group 8 type of use: most of the time
Reference group 9 years of use: never/warming up only
Group 10 years of use: < 1
Group 11 years of use: 1 - 4
Group 12 years of use: 5 - 9
Group 13 years of use: 10 - 19
Group 14 years of use: ≥ 20
Reference group 15 total months of use: never/warming up only
Group 16 total use: 0 - 12.5 months (1st quartile)
Group 17 total use: 12,5 - 35 months (2nd quartile)
Group 18 total use: 35 - 100 months (3rd quartile)
Group 19 total use: 100 - 200 months (4th quartile)
Reference group 20 total use: never/warming up only
Group 21 total use: 0 - 2520 hours (1st quartile)
Group 22 total use: 2520 - 7350 hours (2nd quartile)
Group 23 total use: 7350 - 18000 hours (3rd quartile)
Group 24 total use: 18000 - 66000 hours (4th quartile)


Study size

Type Value
Total 89,527

1,092,578 person-years of follow-up

Statistical analysis method: ( adjustment: )

Conclusion (acc. to author)

During a mean follow-up of 12.2 years, 190 incident cases of thyroid cancer were identified. Overall, 57% of the participants reported the use of electric blankets while sleeping and/or for warming the bed before sleep.
No association was found between use of electric blankets and subsequent risk of thyroid cancer (HR 0.98, CI 0.72-1.32). Duration of electric blanket use measured in years, months, or hours was not associated with the risk of thyroid cancer. These results did not change when the cases were limited to the most frequently occurring histologic type, namely papillary thyroid cancer.
The authors conclude that results of this study do not support possible health hazards of electric blankets in regards to thyroid cancer risk.

Study funded by

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