West Des Moines-based American Equity Investment Life Holding Co., a leading issuer of fixed index annuities, on Thursday reported fourth-quarter net income of $31.2 million, or 39 cents per share, compared with $51 million, or 64 cents per share, a year earlier. Non-GAAP operating income was $50.7 million, compared with $39.8 million for the year-ago quarter. Annuity sales were $1.15 billion compared with third-quarter sales of $1.07 billion, which drove full-year sales to nearly $4.2 billion. For the year, the company had 12 percent growth in policyholder funds under management and a 14 percent non-GAAP operating return on average equity.