She may have died of natural causes. Reports only managed to mention that, Ethel Granger, who had the smallest waist in (recorded) history, measuring a mere 13 inches, passed away in 1982.
She also possibly suffered from an illness due to the damaging effects of tight corsets.
Ethel’s waist was due to her husband, William Granger, who was obsessed with the idea of a wasp-waisted woman. Vogue Italia explains:
Before their marriage Ethel was a plain, unsophisticated twenty-three year old girl who wore the shapeless 1920s dresses that William despised. William told Ethel about his appreciation for corsets, and expressed his wish to feel one around the waist of his wife. One epochal day, when William put his arm around Ethel’s waist she asked “darling, can you feel any difference?”. He could: a pair of corsets that tied Ethel into 24 inches, more or less her natural waist line. The process of Ethel’s waist modification began. Initially Ethel was satisfied with wearing a corset only during the day, but William convinced her to keep it on while sleeping.
Von Sömmerring, a physician and well-known anatomist, argued that the back-laced corset, as worn by fashionable ladies of the time, constituted a health hazard by compressing the ribs and other internal organs and leading—he claimed—to tuberculosis, cancer, and scoliosis, or curvature of the spine.
In 1908, a doctor used X-rays to highlight the damaging effects of tight corsets on a woman's body.
The effect of tight restriction on the lungs was particularly troubling; the lower lobes of the lungs are prevented from expanded fully when taking a breath, resulting in extra strain. This exacerbated lung conditions such as tuberculosis and pneumonia, which effect the lower lungs first, making the condition much more serious -- and both illnesses were much more prevalent before the invention of vaccines in the 20th century. Read more at CNET.com.