With advances in natural language processing and machine learning, researchers are leveraging social media as a low-cost, low-burden method to measure various psychosocial factors. Yet, it is unclear whether information derived from social media is generalizable to broader populations, especially middle-aged and older adults. Using data from the Nurses' Health Study II (2017-2018; n=49,045) including women aged 53-70 years, we assessed differences in sociodemographics, health conditions, behaviors, and psychosocial factors between regular and non-regular Facebook users. We evaluated effect sizes with phi coefficients (Φ; categorical data) or Cohen's ds (continuous data), and calculated odds ratios (OR) with 95% confidence intervals (CI). While most comparisons between users and non-regular users achieved statistical significance in this large sample, effect sizes were mostly "very small" (conventionally defined as <0.01) (e.g., optimism: meanusers=19 versus meannon-regular-users=19, d=-0.03; physical activity: meanusers=24 versus meannon-regular-users=24 metabolic equivalent tasks/week, d=0.01). Some factors had slightly larger differences for users versus non-regular users (e.g., depression: 28% versus 23%; Φ=0.05; OR=1.27, 95% CI=1.22,1.33; obesity: 34% versus 26%; Φ=0.07; OR=1.42, 95% CI=1.36,1.48). Results suggest regular Facebook users were similar to non-regular users across sociodemographic and psychosocial factors, with modestly worse health regarding obesity and depressive symptoms; future research should evaluate other demographic groups.