Cataract surgery is the mainstay of treatment for visually significant cataract. Aside from vision improvement, one secondary benefit of cataract surgery that has been reported is the reduction of fracture risk. This dissertation examines associations between cataract surgery and factors related to fracture risk, including the association between cataract surgery and falls and the association between cataract surgery and long-term mortality.
The first study of this dissertation uses data from the Women’s Health Initiative (WHI) to examine the association between cataract surgery and short and long-term fall frequency in WHI participants with cataract. In the WHI study population, cataract surgery was potentially associated with increased risk of falling at least twice within one year of surgery (odds ratio [OR]=1.06, 95% confidence interval [CI]=0.97, 1.17) and throughout the entire study period (OR=1.10, 95% CI=1.01, 1.19 in repeated measures analysis). In stratified analyses, there were potentially decreased risks of two or more falls within one year after cataract surgery in participants who were older (OR=0.78; 95% CI=0.53, 1.16 for 80-84 years old) or with the highest systemic disease burden (OR=0.80; 95% CI=0.61, 1.05 for Charlson Comorbidity Index [CCI] ≥5), but potentially increased risks in participants who were younger (OR=1.11; 95% CI=0.94, 1.30 for 65-70 years old) or with moderate systemic disease burden (OR=1.17; 95% CI=1.01, 1.35 for CCI 3-4).
The second study examined the association between cataract surgery and long term mortality in the United States (US) Medicare population. In Medicare patients with cataract, patients with cataract surgery had lower adjusted hazards of mortality compared to patients without cataract surgery (hazards ratio [HR]=0.73, 95% CI=0.72, 0.74). The strongest protective associations between cataract surgery and mortality were observed in patients most likely to receive cataract surgery based on high propensity score decile (HR=0.52, 95% CI=0.50, 0.54), patients 80-84 years old (HR=0.63, 95% CI=0.62, 0.65), females (HR=0.69, 95% CI=0.68, 0.70), patients with a moderate systemic disease burden (HR=0.71, 95% CI=0.69, 0.72 for CCI 3-4), and patients with severe cataract (HR=0.68, 95% CI=0.66, 0.70).
The third study examined the association between cataract surgery and long term mortality in WHI participants with cataract, and included additional covariates such as smoking, alcohol use, and body mass index that were not available in the Medicare database. In WHI participants with cataract, there was a protective adjusted association between cataract surgery and mortality (HR=0.60, 95% CI=0.58, 0.63). The strongest protective associations were observed in participants in the highest propensity score decile (HR=0.51, 95% CI=0.40, 0.66), ≥85 years old (HR=0.50, 95% CI=0.36, 0.69), and with a CCI score of 0 or ≥5 (95% CI=0.51, 0.63 for CCI of 0 and 0.51, 0.62 for CCI ≥5).
In conclusion, in patients with cataracts, cataract surgery may be associated with increased risk of falls overall over up to 12 years of follow-up, but decreased risk of falls in older and sicker patients. These findings may partially explain the previously reported protective association between cataract surgery and fracture risk, but there is the need for further study on the association between cataract surgery and fracture risk factors. Additionally, we have found that cataract surgery is associated with improved long term survival in two US populations, and we hypothesize that this may be due to improvement of overall functioning and quality of life after cataract surgery. Further studies of the mechanisms of the protective association between cataract surgery and mortality would be worthwhile in populations within the US and elsewhere.