All analyses were weighted to produce nationally representative estimates. Apart from the joinpoint regression, all other analyses were performed using Stata statistical software (StataCorp LP, 2015) that accounts for the complex survey design of NHIS in the calculation of standard errors and 95% confidence intervals (CI) and in significance testing. All tests of significance were two-tailed, with the level of significance set at 0.05. For better visual presentation, selected estimates and fitted joinpoint regression lines for age 60+ are displayed as figures.
